Chapter 1

Chimpanzee sets the starting point

The closest modern (that is, non-extinct) relatives of humans are chimpanzees. This is unambiguously evidenced by the data of comparative anatomy and molecular genetics, which we talked about a little in the Preface. Paleontological and comparative genetic evidence indicates that the evolutionary lines leading to humans and chimpanzees split about 6–7 million years ago.

Chimpanzees are divided into two species: the common chimpanzee ( Pan troglodytes), living north of the great Congo River, and the pygmy chimpanzee, or bonobo ( pan paniscus), living from it to the south. These species separated from each other no more than 1-2 million years ago, that is, much later than "our", human, the line separated from the ancestors of chimpanzees. It follows that both species of chimpanzee have the same degree of relationship with humans.

Chimpanzees are very important to any popular story about human evolution because they set the starting point. The traits shared by both humans and chimpanzees are of less interest to us than those that only we have. This, of course, is not very logical and smacks of discrimination and xenophobia. Yet books on human evolution rarely begin with a discussion of the important question of why we don't have a tail.

This is of little interest to anyone, because chimpanzees also do not have a tail. And gorillas don't have tails, and orangutans don't, and gibbons don't. This is a common feature of all great apes. This is not our unique feature. What we want to know is why we are so, so special and not at all like those shaggy and wild ones in the zoo.

The story of human evolution usually begins not with the loss of the tail, but with bipedalism - walking on two legs. It seems to be ours, purely human. True, gorillas, chimpanzees and bonobos also sometimes walk like this, although not very often (up to 5–10% of the time). But for everyone except us, such a gait is uncomfortable. Yes, especially and to nothing: the arms are so long, slightly hunched over - and you are already on all fours. Non-human monkeys find it easier to walk on their knuckles, fist, or palm.

Interest in bipedalism clearly shows that it is modern monkeys that set the starting point in the discussion of anthropogenesis. Today, we are well aware that a large and diverse group of bipedal great apes lived and flourished in Africa beginning about 7 million years ago. Their brains were no larger than those of chimpanzees, and it is unlikely that they surpassed chimpanzees in their mental abilities. In a word, they were still quite "inhuman", but already bipedal. If at least one of the species of these monkeys - Australopithecus, Paranthropus, Ardipithecus - accidentally survived to this day (in some African "lost world" - why not?), our bipedalism would inspire us no more than taillessness. And stories about anthropogenesis would begin with something else. Maybe from the manufacture of stone tools (2.6 million years ago). Or from the moment (a little over 2 million years ago) when the brain began to grow.

But all these bipedal non-human apes, unfortunately, died out (except those that turned into people). And so we will not deviate from the accepted tradition and start with bipedalism. We will talk mainly about the history of that group of monkeys that includes us, but does not include chimpanzees. Representatives of this "human" evolutionary line we will call hominids (in the singular - hominid). In fact, there is no consensus among anthropologists about the classification and nomenclature (official group names) of extinct and modern anthropoids. We will stick to one of the options, according to which all representatives of the branch of the evolutionary tree that diverged from the ancestors of chimpanzees 6-7 million years ago and which includes all primates closer to humans than to chimpanzees are classified as hominids. All representatives of this group have now become extinct, except for one single species. Homo sapiens. But in the past there were quite a few of them (see reference table).

Get up and go

Hominid originated in Africa, and all of their early evolution took place there. The conjecture that the fossil ancestors of people lived precisely on the African continent was expressed by Darwin in the book The Origin of Man and Sexual Selection, published in 1871, 12 years after The Origin of Species. At that moment, when in the hands of scientists there was still not a single bone of someone even remotely similar to the transitional link between ape and man, Darwin's guess looked incredibly bold. That it has been confirmed is perhaps one of the most impressive facts in the history of evolutionary biology. Darwin wrote literally the following: “The mammals living in every large region of the world are closely related to the fossil species of the same region. It is therefore possible that now extinct great apes, close to the gorilla and chimpanzee, lived in Africa in the past. Since these two species are closest to man, it seems somewhat more likely that our early predecessors lived on the African continent than elsewhere." Simple, modest and brilliant.

Hominids are characterized by an important common feature - walking on two legs. There are at least as many different hypotheses to explain the transition to bipedalism as there are known reasons for monkeys to sometimes rise to their feet. Monkeys walk vertically, crossing shallow water bodies. Maybe our ancestors became bipedal because they spent a lot of time in the water? There is such a hypothesis. Male monkeys, flirting with females, stand up to their full height and show their penis. Maybe our ancestors wanted to show their genitals all the time? There is such a hypothesis. Females sometimes walk on two legs, pressing the cub to the stomach (if the cub does not sit on its mother's back, clinging to the wool). Maybe it was important for our ancestors to drag two cubs at once, for which they freed their hands? There is also a hypothesis...

And that is not all. There is an assumption that our ancestors sought to increase the viewing range (which became especially important after leaving the forest for the savannah). Or reduce the surface of the body exposed to the sun's rays, again after going out into the savannah. Or it just became fashionable to walk like this - it's cool and the girls like it. This, by the way, is quite plausible: this could happen due to the mechanism of "Fischer's escape", which is discussed in the chapter "The Origin of Man and Sexual Selection". How to choose the right one from this multitude of ideas? Or are several correct at once? Hard to say. Entire articles and even books are devoted to arguments in favor of each of these hypotheses, but none of them has direct evidence.

In such cases, in my opinion, preference should be given to hypotheses that have additional explanatory power, that is, they explain not only bipedalism, but at the same time some other unique features of hominids. In this case, we will have to make fewer controversial assumptions. Below we discuss one of these hypotheses, which seems to me the most convincing. But first you need to get to know the facts.

Traditionally, the last common ancestor of humans and chimpanzees was thought to have preferred to walk on all fours, much like chimpanzees do. Thought that this original (primitive) [The word "primitive" and its antonym "advanced" have a very clear meaning in biology. Primitiveness is relative. It is possible to speak about the primitive and advanced state of a trait only by comparing different organisms with each other. Primitive means more similar to what the common ancestor of the compared species had] the mode of locomotion was preserved in chimpanzees (as well as gorillas and orangutans), and in our evolutionary line it was replaced by bipedalism in connection with the exit from the forest into the open savannah. Recently, however, there have been suspicions that perhaps the last common ancestor of man and chimpanzee, if not bipedal, then at least showed a greater propensity for upright walking than modern chimpanzees and gorillas. This possibility is unambiguously hinted at by new paleoanthropological finds.

In recent years, fossils of several very ancient hominids have been discovered in Africa that lived around the same time that the evolutionary lines leading to chimpanzees and humans separated. The classification of these forms remains controversial. Although they are described as members of three new genera ( Sahelanthropus, Orrorin, Ardipithecus) some experts believe that some of them should be combined with each other or with a later genus Australopithecus. In particular, it was proposed to unite Orrorin, Ardipithecus and several species of primitive Australopithecus into the genus Praeanthropus. But these disputes are not very interesting for us: in the end, call it what you want, the main thing is to understand what kind of creatures they were, how they lived and how they changed over the course of generations.

The most interesting thing about these ancient hominids is that they all probably already walked on two legs (although not as confidently as we do), but they did not live in the open savannah, but in a not very dense forest or in a mixed landscape, where forest areas alternated with open ones. This, in principle, does not contradict the old theory that the development of bipedality was associated with gradual the transition of native forest dwellers to life in open areas.

SAHELANTROP [reference data for the hominin species mentioned in the text are summarized in the table on p. 449]. Among the most important recently discovered forms is Sahelanthropus tchadensis, described from the skull, several jaw fragments, and individual teeth. All this was found in 2001-2002 in northern Chad by French anthropologists led by Michel Brunet. The skull was given the unofficial nickname Tumai, which in the local dialect means "a child born before the onset of the drought season." Such nicknames are given to their findings of paleoanthropology for advertising purposes. Unfortunately, no fragments of the postcranial skeleton [postcranial skeleton - the entire skeleton except the skull] it has not been officially reported, although there are rumors that a fragment of the femur was also found. The age of the find is 6–7 million years. Tumai, in principle, does not contradict the ideas of what a common ancestor of humans and chimpanzees might look like. [although in many ways Tumai’s skull resembles a gorilla (S. V. Drobyshevsky, personal communication)] And most importantly, he is quite suitable for this role for his age. But he may end up being the oldest ancestor of a chimpanzee or a gorilla, or a very early representative of "our" line, that is, hominids. Tumay's brain volume is very small (approximately 350 cm3). On this basis, he does not stand out from other non-human anthropoids at all.

Three features of the Sahelanthropus are of particular interest. The first is the position of the foramen magnum, which is shifted forward compared to other anthropoids. Perhaps this means that Toumai already walked on two legs quite often, and therefore the spine was attached to the skull not from behind, but rather from below. The second interesting point is that the Sahelyantrop, judging by the associated fossil flora and fauna, did not live in the open savannah, but on the shores of an ancient lake, in a mixed landscape where open areas alternated with forest ones. Fossil remains of lake, forest and savannah animals have been found in the vicinity of the Sahelanthrope. The third important feature is the small size of the fangs. They are comparable to the fangs of female chimpanzees, but much smaller than those of males. The size of the fangs in male anthropoids allows us to judge some aspects of social life (more on this will be discussed below in the section on Ardipithecus). But, since there is only one skull and we do not know what gender Toumai was, it is not yet worth drawing far-reaching conclusions from small fangs.

The find showed that ancient hominids or forms close to them were more widespread in Africa than was thought: almost all previous finds were made in the so-called Great Rift Valley, stretching from north to south in East and South Africa.

ORRORIN. Another important find Orrorin tugenensis, found in 2000 in Kenya by French researchers led by Brigitte Senyu and Martin Pickford. Nickname - Millennium man(millennial man), age - about 6 million years. This is also a form close to the common ancestor of man and chimpanzee. As in the case of the Sahelanthropus, the bone material for this species is still fragmentary and not numerous. However, professional zoologists and anthropologists are well aware of how much information about the structure of a mammal can be extracted even from a few scattered bones. [the tale is widely known about how the great paleontologist Georges Cuvier accurately restored the appearance of the entire animal from one bone. This, of course, is an exaggeration, but there is some truth here: different parts of the animal are interconnected, and therefore changes in some parts in many cases are reflected in others. This is called the principle of correlation. However, it should not be absolutized: within certain limits, different parts of the skeleton can change independently of each other]. The skulls of Orrorin have not yet been found, but anthropologists have concluded that walking on two legs based on the structure of the hip. Judging by the accompanying fossil flora and fauna, Orrorin did not live in open savannah, but in a dry, evergreen forest. Found a handful of scattered teeth, similar to the teeth of later hominids. Among them is one canine (upper right). It is small, about the size of a female chimpanzee.

In general, it became clear that upright walking, most likely, was mastered by our ancestors for a very long time. Almost immediately after the separation of the lines of man and chimpanzee, representatives of "our" line already walked on two legs. Or maybe it happened even earlier? What if the common ancestors of humans and chimpanzees already preferred to walk on their hind limbs, and the current chimpanzee manner of walking, leaning on the knuckles of the fingers, developed later? This assumption is hindered by the fact that gorillas and orangutans also rely on their hands when walking. If we assume that bipedalism was the original, primitive condition for the ancestors of chimpanzees, then we have to admit that subsequently representatives of this evolutionary line, independently of gorillas, acquired a gait very similar to the gorilla. There is nothing incredible about this. True, biologists try to avoid as far as possible the assumption of the independent appearance of the same trait in different evolutionary lines. This is called the principle of parsimony, or the economy of hypotheses. But in this case, according to many anthropologists, this principle does not work: most likely, "bone walking" really developed independently among orangutans, gorillas and chimpanzees.

ORANGUTANS WALK LIKE PEOPLE. Recently, there is a growing body of evidence suggesting that bipedal walking may not be derived from the way chimpanzees and gorillas walk on their knuckles at all.

From what then to deduce it? Perhaps one of those modes of locomotion that developed among great apes at the stage of life on trees. For example, it has recently been shown that the most reminiscent of human gait is the manner of orangutans moving on two legs, holding hands on branches.

It has been previously suggested that the skeleton and musculature of our ancestors were pre-adapted (predisposed) to bipedal walking due to tree-climbing skills. At the same time, the body is oriented vertically, and the legs make movements reminiscent of those made when walking. However, anthropologist Robin Crompton of the University of Liverpool and his colleagues Susanna Thorpe and Roger Holder of the University of Birmingham believe that it is difficult to deduce human bipedal gait from vertical tree-climbing, as well as from the gait of chimpanzees and gorillas. There are significant differences in the mechanics of these movements. For example, the knees of chimpanzees and gorillas almost never fully extend. As we already know, these monkeys sometimes move on the ground on two legs, but the legs remain half-bent. Their gait differs from the human and a number of other features. Another thing is orangutans, the most "arboreal" of the large anthropoid [meaning a natural group including orangutans, gorillas, chimpanzees and hominids. In English, this group is called great apes], whose behavior Crompton and his colleagues observed during the year in the forests of the island of Sumatra.

Anthropologists have registered 2811 single "acts" of movement of orangutans in the crowns of trees. For each case, the number of supports (branches) used, their thickness, as well as the method of movement were recorded. Orangutans have three such ways: on two legs (holding on to something with a hand), on all fours, clasping a branch with their fingers and toes, and on one hand, in a suspended state, from time to time grabbing something with their feet.

Statistical analysis of the collected data showed that the method of movement depends on the number and thickness of supports. On single thick, strong branches, orangutans usually move on all four, along branches of medium diameter - on their hands. On thin twigs, they prefer to carefully walk with their feet, holding on to some additional support with their hand. At the same time, the gait of the monkeys is very similar to the human one - in particular, the legs are fully extended at the knees. It is this mode of movement that seems to be the safest and most efficient when you need to move along thin, flexible and unreliable branches. An additional advantage is that one of the hands remains free to pick the fruit.

The ability to walk on thin branches is no small thing for tree monkeys. Thanks to this ability, they can move freely along the forest canopy and move from tree to tree without descending to the ground. This significantly saves strength, that is, reduces the energy costs for the extraction of food. Therefore, this ability must be supported by natural selection.

Orangutans separated from the common evolutionary trunk before gorillas, and gorillas before this trunk split into the ancestors of chimpanzees and humans. The researchers suggest that bipedal walking along thin branches was originally inherent in the distant ancestors of all large anthropoids. Orangutans living in the tropical rain forests of Southeast Asia retained and developed this skill, gorillas and chimpanzees lost it, developing in return their characteristic four-legged walking on the knuckles and the rarely used bipedal “half-bent” gait. This could be facilitated by the periodic "drying" of tropical forests in Africa and the spread of savannahs. Representatives of the human evolutionary line have learned to walk on the ground in the same way as on thin branches, straightening their knees.

According to Crompton and his colleagues, their assumption explains two groups of facts that seem rather mysterious from the point of view of other hypotheses for the origin of bipedality. First, it becomes clear why forms close to the common ancestor of humans and chimpanzees (such as the Sahelanthropus, Orrorin, and Ardipithecus) already have clear signs of bipedalism in the structure of the skeleton, and this despite the fact that these creatures did not live in the savannah. but in the forest. Secondly, the structure of the arms and legs of the Afar Australopithecus, the most well-studied of the early representatives of the human line, ceases to seem contradictory. At Australopithecus afarensis the legs are well adapted for bipedal walking, but the arms are very long, prehensile, more suitable for living in trees and grasping branches (see below).

According to the authors, humans and orangutans retained the ancient bipedal gait of their distant ancestors, while gorillas and chimpanzees lost it and developed something new instead - walking on the knuckles. It turns out that in this respect, humans and orangutans should be considered "primitive", and chimpanzees and gorillas - "evolutionarily advanced" ( Thorpe et al., 2007).

The magnificent Ardi, the oldest of the well-studied (today) hominids, brings even more clarity to the question of the origin of bipedalism.

In October 2009, a special issue of the journal Science was published, dedicated to the results of a comprehensive study of the bones of Ardipithecus, a bipedal monkey that lived in northeastern Ethiopia 4.4 million years ago. View Ardipithecus ramidus was described in 1994 from several teeth and jaw fragments. In subsequent years, the collection of bone remains of Ardipithecus was significantly enlarged and now includes 109 specimens. The greatest success was the discovery of a significant part of the female skeleton, which scientists solemnly presented to journalists and the general public under the name of Ardi. In official documents, Ardi is listed as the ARA-VP-6/500 skeleton.

Eleven articles published in the special issue of Science summed up many years of work by a large international research team. The publication of these articles and their protagonist Ardi were widely publicized, but this is by no means an empty hype, because the study of the bones of Ardipithecus really allowed us to reconstruct the early stages of hominid evolution in more detail and more accurately.

The assumption, made earlier on the basis of the first fragmentary finds, was confirmed that A. ramidus- an excellent candidate for the role of a transitional link [a candidate, not just a transitional link, because one cannot rigorously prove from fossil bones that someone was someone's ancestor or descendant. However, in many cases this can be judged with a high degree of certainty, as, for example, in the case of Ardi] between the common ancestor of humans and chimpanzees (apparently, Orrorin and Sahelantrop were close to this ancestor) and later hominids - Australopithecus, from which, in turn, the first representatives of the human genus descended ( Homo).

Up until 2009, the oldest known hominin in detail was Lucy, an Afar australopithecine that lived about 3.2 million years ago ( Johanson, Go, 1984). More and more ancient species (in ascending order of antiquity: Australopithecus anamensis, Ardipithecus ramidus, Ardipithecus kadabba, Orrorin tugenensis, Sahelanthropus chadensis) were studied on the basis of fragmentary material. Accordingly, our knowledge of their structure, lifestyle and evolution also remained fragmented and inaccurate. And now the honorary title of the most ancient of the well-studied hominids solemnly passed from Lucy to Ardi.

DATING AND FEATURES OF THE BURIAL. Bones A. ramidus come from a single layer of sedimentary deposits about 3 m thick, enclosed between two volcanic layers. The age of these interlayers was determined using the argon-argon method. [one of the most reliable methods for radiometric dating of volcanic rocks. It is the result of an improvement in the potassium-argon method, based on the constancy of the rate of transformation of the radioactive isotope 40 K into 40 Ar] and turned out to be the same (within the measurement error) - 4.4 million years. This means that the bone layer was formed (as a result of floods) relatively quickly - at most in 100,000 years, but most likely - in several millennia or even centuries.

The excavations began in 1981. In total, more than 140,000 samples of vertebrate bones have been obtained, of which 6000 can be identified to the family. Among them - 109 samples A. ramidus belonging to at least 36 individuals. Fragments of Ardi's skeleton were scattered over an area of ​​about 3 m 2 . The bones were unusually fragile, so extracting them from the rock cost a lot of work. The cause of Ardi's death has not been determined. She was not eaten by predators, but her remains appear to have been thoroughly trampled on by large herbivores. Especially went to the skull, which was crushed into many fragments.

ENVIRONMENT. Along with the bones A. ramidus remains of various animals and plants have been found. Among plants, forest ones predominate, among animals - eating leaves or fruits of trees (rather than grass). Judging by these finds, Ardipithecus did not live in the savanna, but in a wooded area, where areas of dense forest alternated with thinner ones. The ratio of carbon isotopes 12 C and 13 C in the tooth enamel of five individuals A. ramidus indicates that the Ardipithecus ate mainly the gifts of the forest, and not the savanna (savanna grasses are characterized by an increased content of the 13 C isotope). In this, the Ardipithecus differ from their descendants, Australopithecus, who received from 30 to 80% of carbon from open space ecosystems (Ardipithecus - from 10 to 25%). However, the Ardipithecus were still not purely forest dwellers, like chimpanzees, whose food is almost 100% forest origin.

The fact that the Ardipithecus lived in the forest at first glance contradicts the old hypothesis that the early stages of hominin evolution and the development of bipedal walking were associated with leaving the forest for the savannah. Similar conclusions had previously been made in the course of the study of Orrorin and Sahelantrop, which also apparently walked on two legs, but lived in a wooded area. However, this situation can be looked at from another point of view, if we remember that the forests in which the early hominids lived were not very dense, and their bipedal walking was not very perfect. According to S. V. Drobyshevsky, the combination of "transitional environment" with "transitional gait" does not refute, but, on the contrary, brilliantly confirms the old views. Hominids moved from dense forests to open spaces gradually, and their gait improved just as gradually.

SKULL AND TEETH. Ardi's skull is similar to that of the Sahelanthrope. Both species are characterized by a small brain volume (300–350 cm 3), a large occipital foramen displaced forward (that is, the spine was attached to the skull not from behind, but from below, which indicates bipedal walking), as well as less developed than in chimpanzees and gorillas , molars and premolars. Apparently, the pronounced prognathism (protrusion of the jaws forward) in modern African great apes is not a primitive trait and developed in them after their ancestors separated from human ancestors.

The teeth of an ardipithecus are the teeth of an omnivore. The whole set of features (the size of the teeth, their shape, the thickness of the enamel, the nature of microscopic scratches on the tooth surface, the isotopic composition) indicates that the ardipithecus did not specialize in any one diet - for example, on fruits, like chimpanzees. Apparently, the Ardipithecus fed both in trees and on the ground, and their food was not too hard.

One of the most important facts is that males A. ramidus, unlike modern anthropoids (except humans), fangs were no larger than those of females. Male monkeys actively use fangs both to intimidate rivals and as a weapon. In the most ancient hominids ( Ardipithecus kadabba, Orrorin, Sahelanthropus) the fangs of males may also have been no larger than those of females, although there is not yet enough data for final conclusions. Obviously, in the human evolutionary line, sexual dimorphism (between-sex differences) in the size of fangs came to naught very early. We can say that in males there was a "feminization" of fangs. In chimpanzees and gorillas, dimorphism seems to have increased a second time, males have acquired very large fangs. Male bonobos have smaller fangs than other modern apes. Bonobos are also characterized by the lowest level of intraspecific aggression. Many anthropologists believe that there is a direct relationship between male canine size and intraspecific aggression. In other words, it can be assumed that the decrease in fangs in our distant ancestors was associated with certain changes in the social structure. For example, with a decrease in conflicts between males.

BODY SIZE. Ardi's height was about 120 cm, weight - about 50 kg. Males and females of Ardipithecus almost did not differ in size. Weak sexual dimorphism in body size is also characteristic of modern chimpanzees and bonobos with their relatively equal relations between the sexes. Gorillas, on the other hand, have a very pronounced dimorphism, which is usually associated with polygamy and a harem system. In the descendants of the Ardipithecus, the Australopithecus, sexual dimorphism may have increased (see below), although this was not necessarily due to the dominance of males over females and the establishment of a harem system. The authors speculate that males may have grown and females shredded due to going out into the savannah, where males had to take over the protection of the group from predators, and females may have learned to cooperate better with each other, which made physical strength less important for them. .

POSTCRANIAL SKELETON. Ardi moved on the ground on two legs, although less confidently than Lucy and her relatives - Australopithecus. At the same time, Ardi retained many specific adaptations for effective tree climbing. In accordance with this, in the structure of the pelvis and legs of Ardi, a combination of primitive (climbing-oriented) and advanced (walking-oriented) signs is observed.

Ardi's hands are exceptionally well preserved (unlike Lucy's). Their study allowed us to draw important evolutionary conclusions. As we already know, it has long been believed that human ancestors, like chimpanzees and gorillas, walked on their knuckles. This peculiar way of locomotion is characteristic only of African great apes and orangutans; other monkeys, when walking, usually rely on the palm of their hand. However, Ardi's hands are devoid of specific features associated with "bone-walking". The Ardipithecus hand is more flexible and mobile than that of the chimpanzee and gorilla, and is similar to the human one in a number of ways. It is now clear that these characters are primitive, original to hominids (and possibly to a common ancestor of humans and chimpanzees). The structure of the hand, characteristic of chimpanzees and gorillas (which, by the way, does not allow them to manipulate objects as deftly as we do), on the contrary, is advanced, specialized. The strong, grasping hands of chimpanzees and gorillas enable these massive animals to move efficiently through trees, but are ill-suited for fine manipulation. The hands of the Ardipithecus allowed him to walk along the branches, leaning on his palms, and were better suited for tool activities. Therefore, in the course of further evolution, our ancestors did not have to "remake" their hands so much.

In the structure of the Ardipithecus foot, a mosaic of signs is observed, indicating the preservation of the ability to grasp branches (opposed thumb) and, at the same time, effective bipedal walking (harder than in modern great apes, the arch of the foot). The descendants of the Ardipithecus, the Australopithecus, lost the ability to grasp branches with their feet and acquired an almost completely human structure of the foot.

Ardipithecus brought many surprises to anthropologists. According to the authors, no one could have predicted such a mixture of primitive and advanced features, which was found in Ardipithecus, without real paleoanthropological material in their hands. For example, it never occurred to anyone that our ancestors first adapted to walk on two legs due to the transformation of the pelvis and only then abandoned the opposing thumb and grasping function of the feet.

Thus, the study of Ardipithecus has shown that some popular hypotheses about the evolutionary paths of hominids need to be revised. Many features of modern anthropoids turned out to be not at all primitive, but advanced, specific features of chimpanzees and gorillas, associated with deep specialization in climbing trees, hanging on branches, "bone walking", and a specific diet. These signs were not in our common ancestors with them. Those monkeys from which man descended were not very similar to the current ones.

Most likely, this applies not only to the physical structure, but also to behavior and social structure. Perhaps chimpanzee thinking and social relationships are not such a good model for reconstructing the thinking and social relationships of our ancestors. In the concluding article of the special issue of Science, the famous American anthropologist Owen Lovejoy calls for a rejection of the usual notion that Australopithecus was something like a chimpanzee who learned to walk upright. Lovejoy emphasizes that in reality chimpanzees and gorillas are extremely peculiar, specialized, relic primates that have taken refuge in impenetrable tropical forests and that is the only reason they have survived to this day. Based on the new facts, Lovejoy developed a very interesting model of the early evolution of hominids, which will be discussed in the next section.

Family relationships are the key to understanding our evolution

Most hypotheses about the ways and mechanisms of anthropogenesis traditionally revolve around two unique features of people: a large brain and complex tool activity. Owen Lovejoy is one of those anthropologists who believe that the key to understanding our origins is not an enlarged brain or stone tools (these signs appeared very late in the evolution of hominids), but other unique features of the "human" evolutionary line associated with sexual behavior. , family relations and social organization. Lovejoy argued this point of view as early as the early 1980s. At the same time, he suggested that the key event in the early evolution of hominids was the transition to monogamy, that is, to the formation of stable marriage pairs ( Lovejoy 1981). This assumption was then repeatedly challenged, revised, confirmed and denied ( Butovskaya, 2004) [the largest Russian anthropologist M.L. Butovskaya believes that our distant ancestors most likely practiced the so-called serial monogamy. This type of relationship is characteristic of modern European civilization: they got married, lived together for several years (on average, about as long as it takes to raise a child), then divorced and changed partners. Similar practices are found among modern hunter-gatherers such as the Hadza in Tanzania].

New data on Ardipithecus have strengthened the case for the leading role of changes in social and sexual behavior in the early evolution of hominids. A study of the Ardipithecus has shown that the chimpanzee and gorilla are not the best reference points for reconstructing the thinking and behavior of our ancestors. As long as Lucy remained the oldest well-studied hominin, it could still be assumed that the last common ancestor of humans and chimpanzees was broadly similar to chimpanzees. Ardi radically changed this situation. It became clear that many features of chimpanzees and gorillas are relatively recently acquired specific features of these relic primates. Human ancestors did not have these characteristics. If this is true of feet, hands, and teeth, then it may well be true of behavior and family relationships. Therefore, we should not start from the belief that the social life of our ancestors was about the same as that of today's chimpanzees. Chimpanzees aside, we can focus on the information provided by fossil material.

Lovejoy attaches great importance to the fact that Ardipithecus males, as already mentioned, did not have large fangs that could, like other monkeys, constantly sharpen on the molars of the lower jaw and be used as a weapon and a means of intimidating male competitors. The reduction of fangs in later hominids - Australopithecus and humans - has previously been interpreted either as a by-product of the increase in molars (molars) or as a consequence of the development of the stone industry, which made this natural weapon redundant. It has long been clear that the fangs were reduced long before the start of the production of stone tools (about 2.6 million years ago). The study of Ardipithecus showed that the decrease in fangs also occurred long before the molars increased in Australopithecus (which was possibly associated with going out into the savannah and with the inclusion of hard rhizomes in the diet). Therefore, the hypothesis about the social causes of the decrease in fangs began to look more convincing. Large fangs in male primates are a reliable indicator of intraspecific aggression. Therefore, their decrease in early hominids most likely indicates that relations between males have become more tolerant. They became less at enmity with each other because of females, territory, dominance in the group.

Great apes in general are characterized by the so-called K-strategy . Their reproductive success depends not so much on fertility as on the survival of the young. Humanoids have a long childhood, and females spend a huge amount of time and energy to raise each cub. While the female is nursing the cub, she is not able to conceive. As a result, males are constantly faced with the problem of a shortage of "conditioned" females. Chimpanzees and gorillas solve this problem by force. Male chimpanzees unite in combat squads and raid the territories of neighboring groups, trying to expand their possessions and gain access to new females. Male gorillas expel potential competitors from the family and strive to become the sole masters of the harem. For both, large fangs are not a luxury, but a means to leave more offspring. Why did the early hominids abandon them?

Another important component of the reproductive strategy of many primates is the so-called sperm wars. They are characteristic of species that practice free sexual relations in groups that include many males and females. Large testes are a reliable indicator of sperm wars. Gorillas, with their well-guarded harems, and loner orangutans (also hardcore polygamists, although their mates usually live apart, not as a single group) have relatively small testes, like humans. Sexually liberated chimpanzees have huge testes. Important indicators are also the rate of sperm production, the concentration of spermatozoa in it and the presence of special proteins in the seminal fluid that create obstacles for foreign spermatozoa. Based on the totality of all these signs, it can be concluded that in the evolutionary history of man, regular sperm wars were once, but have not played a significant role for a long time.

If early male hominids didn't squabble over females and get into sperm wars, then they must have found some other way to ensure their reproductive success. This method is known, but it is quite exotic - it is practiced by only about 5% of mammals. This is monogamy - the formation of strong married couples. Males of monogamous species, as a rule, take an active part in caring for offspring.

Lovejoy believes that monogamy may have evolved from behaviors found in some primates, including (albeit infrequently) chimpanzees. We are talking about "mutually beneficial cooperation" of the sexes based on the principle of "sex in exchange for food." This behavior may have developed particularly strongly in early hominids due to the peculiarities of their diet. Ardipithecus were omnivores, foraging both in trees and on the ground, and their diet was much more varied than that of chimpanzees and gorillas. It must be borne in mind that in monkeys omnivorousness is not a synonym for promiscuity in food - on the contrary, it implies high selectivity, a gradation of food preferences, and an increase in the attractiveness of certain rare and valuable food resources. Leaf- and fruit-eating gorillas can afford to wander lazily through the forest, moving only a few hundred meters a day. The omnivorous Ardipithecus had to be more energetic and travel much longer distances to get something tasty. At the same time, the danger of falling into the teeth of a predator increased. It was especially hard for females with cubs. Under such conditions, the "sex for food" strategy became very advantageous for females. Males who fed females also increased their reproductive success, as their offspring had an improved chance of survival.

Chimpanzees steal fruits from other people's gardens to seduce females

An international team of zoologists from the US, UK, Portugal and Japan observed a family of wild chimpanzees in the forests around the village of Bossu in Guinea, near the border with Côte d'Ivoire and Liberia, for two years. These observations made it possible to judge the relationship among wild chimpanzees , not spoiled by annoying human attention and training.

The territory of the family occupied an area of ​​approximately 15 km 2 and closely adjacent to human habitation. The economy of the people included plantations of fruit trees. The family of chimpanzees at different times numbered from 12 to 22 individuals, of which there are always only three males. These males constantly raided fruit plantations. On average, each male climbed into someone else's garden 22 times a month. The males understood the danger of an illegal enterprise, showing their alarm with a characteristic scratching. Going to work, the male looked around all the time - if there was any surveillance, then quickly climbed a tree, instantly plucked two fruits - one in the teeth, the other in the hand - and quickly, quickly from the dangerous territory.

Chimpanzee thieving raids look just like boyish forays into a neighboring orchard for apples. And the purpose of these raids, as it turned out, is not too different from boyish thoughts: to boast of prey to comrades and to appear as heroes to girls. Chimpanzees don't bring stolen fruit to their family to devour it in a corner. Males feed them to females!

It must be remembered that chimpanzees, like other apes, rarely share food with each other (except, of course, mothers and cubs). And the food is not free. It is offered by males to females ready to mate. Females behave correctly and do not ask for treats, the male himself chooses whom to treat. As we can see, the "sex for food" strategy in promiscuous chimpanzee communities can also work, although not as effectively as in monogamy.

In this family, one of the females was clearly superior to the others in terms of attractiveness. In 83% of cases, the males treated her with fruits. After that, the female, accepting courtship, moved away with the chosen one to the borders of the territory. At the same time, she clearly preferred the courtship of one of the applicants, and this was not at all a dominant alpha male, but a subordinate beta male: she spent more than half of her time with him. The dominant male was less likely than others to share ill-gotten fruits with her: only in 14% of cases did he invite her to treat herself.

Observers also note the following fact: males preferred this particular female, despite the fact that the family also had another, physiologically more prepared for reproduction. The uninvited thought immediately comes to mind that male chimpanzees evaluated their girlfriends not only by readiness for breeding, but also by other subjective criteria, but, naturally, the authors of the publication refrained from such speculation. These remarkable observations nevertheless led them to the well-founded conclusion that for chimpanzees, stealing is not a way to get their own food. After all, they do not share "real", forest food. This is a way to maintain your authority, as is characteristic of a dominant male, or to win the sympathy of females ( Hockings et al., 2007).

If males of ancient hominids made it a rule to carry food to females, then over time, special adaptations should have developed to facilitate this behavior. [In animals as intelligent as monkeys, behavior may first change, and the change will persist through generations through imitation and learning, as a cultural tradition. This leads to a change in the direction of selection, because mutations that make life easier with just such behavior will now be supported and distributed. As a result, this can lead to the consolidation of new psychological, physiological and morphological features. This way of forming evolutionary innovations is called the Baldwin effect. We will talk about it in more detail in the following chapters]. The extracted tidbits had to be carried over considerable distances. It's not easy if you walk on all fours. Lovejoy believes that bipedalism, the most striking distinguishing feature of hominids, developed precisely in connection with the custom of supplying food to females. An additional incentive could be the use of primitive tools (for example, sticks) to pick out hard-to-reach food items.

The changed behavior had to affect the nature of social relations in the group. The female was primarily interested in the fact that the male would not leave her, the male - that the female would not cheat on him. The achievement of both goals was desperately hampered by the female primate's way of "advertising" ovulation, or the time when a female is fertile. Such advertising is beneficial if the society is organized like a chimpanzee. But in a society with a predominance of stable pair bonds that have developed on the basis of the "sex for food" strategy, the female is absolutely not interested in arranging long periods of abstinence for her male (she will stop feeding or even leave for another, scoundrel!). Moreover, it is beneficial for the female that the male could not determine at all whether conception is possible at the moment. Many mammals determine this by smell, but in hominids, selection has reduced many olfactory receptors. Males with an impaired sense of smell fed their family better - and became more desirable marriage partners.

The male, for his part, is also not interested in his female advertising her readiness for conception and creating unnecessary excitement among other males - especially if he himself is currently "on the hunt." Females who concealed ovulation became preferred partners because they had fewer reasons for adultery.

As a result, female hominids lost all outward signs of readiness (or unreadiness) for conception; including, it became impossible to determine by the size of the mammary glands whether the female now has a nursing calf. In chimpanzees, as in other primates (except humans), the size of the mammary glands indicates whether the female is fertile. Enlarged breasts are a sign that the female is now feeding the cub and cannot conceive a new one. Male chimpanzees rarely mate with lactating females, and their enlarged breasts do not appeal to them.

Humans are the only primates whose females have permanently enlarged breasts (and some males like it). But why did this trait develop in the first place - to attract males or, perhaps, to discourage them? Lovejoy believes the second option is more plausible. He believes that the constantly enlarged breasts, which do not give any information about the female's ability to conceive, were part of a set of measures to strengthen monogamy and reduce hostility between males.

As pair bonds strengthened, the preferences of females should have gradually shifted from the most aggressive and dominant males to the most caring. In animal species in which males do not take care of the family, choosing the most "cool" (dominant, courageous) male often turns out to be the best strategy for the female. Paternal care for offspring radically changes the situation. Now it is much more important for the female (and her offspring) that the male is a reliable breadwinner. External signs of masculinity (masculinity) and aggressiveness, such as large fangs, begin to repel rather than attract females. A male with large fangs is more likely to increase his reproductive success by force, by fighting other males. Such husbands go out of fashion when a diligent and reliable husband-breadwinner is needed for the survival of the offspring. Females who choose fighter husbands raise fewer cubs than those who choose non-aggressive laborers. As a result, females begin to prefer males with small fangs - and under the influence of sexual selection, fangs rapidly decrease.

Sad ladies choose not the most courageous gentlemen

Few biologists would deny that mate-selection adaptations play a huge role in evolution (see the chapter "Human Origins and Sexual Selection"). However, there are still many gaps in our knowledge of these adaptations. In addition to purely technical difficulties, their study is hampered by stereotypes. For example, researchers often overlook such a seemingly obvious possibility that mating preferences in different individuals of the same species do not have to be the same at all. It seems natural to us to think that if, for example, the average peacock prefers males with large and bright tails, then this must certainly be true for all peacocks at all times. But this is not necessarily the case. In particular, the so-called choice with an eye on oneself is possible - when an individual prefers partners that are somewhat similar or, conversely, not similar to itself. Moreover, even in the same individual, preferences can change depending on the situation - for example, on the degree of stress or on the phase of the estrous cycle.

A good choice of a sexual partner is a matter of life and death for your genes, which in the next generation will have to mix with the genes of your chosen one. This means that any hereditary changes that even slightly affect the optimal choice will be extremely intensively supported or, conversely, rejected by natural selection. Therefore, we have the right to expect that the algorithms for choosing a partner, which have developed in the course of evolution in different organisms, can be very sophisticated and flexible. These considerations are quite applicable to people. Research in this area can help find a scientific approach to understanding the most subtle nuances of human relationships and feelings. However, few such studies have been carried out so far.

Recently, two seemingly unrelated articles appeared in the journals Evolutionary Psychology and BMC Evolutionary Biology. One work was done on humans, the other on house sparrows, but the patterns revealed in them are similar. This at least makes you think.

Let's start with sparrows. These birds are monogamous, that is, they form stable pairs, and both parents take care of the offspring, but adultery is common. In short, family relationships in sparrows differ little from those accepted in most human populations. In male house sparrows, the main sign of masculinity is a black spot on the chest.

It is shown that the size of the spot is an "honest" indicator of the health and strength of the male (which depend on the quality of the genes) and is directly related to his social status. Males with a large spot occupy the best areas, successfully defend their female from the encroachments of other males and produce more offspring on average than males with a small spot. It is also shown that the reproductive success of females who have linked their lives with the owner of a large spot, in most populations, is on average higher than that of "losers" who got a less bright male as their husband.

From these facts, it would seem that sparrows should always and under any circumstances prefer males with a large spot. Austrian scientists from the Institute of Ethology im. Konrad Lorenz in Vienna. They suggested that females' preferences might depend on their own condition. In particular, it was expected that females in poor physical condition might be less picky. Reduced selectivity in unattractive individuals has previously been noted in several animal species.

As a measure of the physical condition of the female, the ratio of body weight to the length of the metatarsus, erected in a cube, was used. This indicator simply reflects the fatness of the bird, which, in turn, depends on its health and on the conditions in which it grew. It is known that this value in passerine birds is positively correlated with indicators of female reproductive success, such as clutch size and the number of surviving chicks.

The experiment involved 96 sparrows and 85 sparrows caught in the Vienna Zoo. The initial size (length) of the black spot in all males selected for the experiment was less than 35 mm. Half of the males were painted with a black marker up to 35 mm, which roughly corresponds to the average size of the spot in males of this species, and the other half - up to 50 mm, which corresponds to the maximum size. Female preferences were determined by the standard method commonly used in such studies. Two males with different spot sizes were placed in the two outer enclosures, and a female was placed in the central enclosure, and it was looked at which of the males the female would spend more time next to.

It turned out that between the fatness of the female and the time she spends next to the "worst" of the two males, there is a strong negative correlation. In other words, the worse the condition of the female, the less time she spends next to the owner of a large spot and the stronger her craving for a male with a medium-sized spot. At the same time, contrary to theoretical expectations, well-fed females did not demonstrate clear selectivity. They spent, on average, about the same amount of time near each of the two males. The stunted females, on the other hand, showed a strong selectivity: they strongly preferred "average" males and avoided those with a huge spot.

This appears to be one of the first ethological studies to demonstrate a preference for "second-class" females over low-quality males. A similar result was obtained on zebra finches, and this work was also published quite recently ( Holveck, Riebel, 2010). Earlier, something similar was seen in stickleback fish ( Bakkeret et al., 1999). Unlike Viennese sparrows, female finches and sticklebacks that are in good shape clearly prefer "high quality" males.

The authors suggest that the odd preference for skinny sparrows may be due to the fact that males with little spotting are more caring fathers. Some facts and observations indicate that weak males with a small spot try to compensate for their shortcomings by taking on more parental chores. A strong sparrow, in principle, can raise chicks without the help of a spouse, so she can afford to take a healthy and strong male with a large spot as her husband, even if he is a bad father, in the hope that the offspring will inherit his health and strength. A weak female cannot cope alone, so it is more profitable for her to choose a less “prestigious” spouse if there is hope that he will spend more energy on the family. Isn't this somewhat reminiscent of the situation, according to Lovejoy, among the Ardipithecus?

Previous research has shown that female sparrow preferences may vary among sparrow populations. In some populations, females, on average, as expected by theory, prefer males with the largest spots. In others, this is not observed (as in the population of the Vienna Zoo). According to the authors, this variability is partly due to the fact that in different populations there may be a different numerical ratio of females in good and bad physical shape ( Griggio, Hoi, 2010).

A similar study, but not on sparrows, but on humans, was performed by psychologists from Oklahoma State University. They studied the influence of thoughts about death on how women evaluate the attractiveness of male faces, which differ in the degree of masculinity (masculinity).

If we talk about "average" preferences, then women tend to prefer more masculine faces if they themselves are in that phase of the menstrual cycle when the likelihood of conception is high. Women who are less likely to conceive tend to prefer men with more feminine faces.

The interest of psychologists in the effects of death reminders is due to the fact that, as numerous observations and experiments have shown, such reminders have a profound effect on the reproductive behavior of people. One of the manifestations of this influence is birth rate surges, often observed after major catastrophes or natural disasters. Reminders of the inevitability of death exacerbate people's interest in the reproductive sphere and stimulate the desire to have children. For example, if subjects are reminded that they are mortal before testing, the percentage of positive answers to questions like "Would you like to have another child?" increases noticeably. Quite a few such studies have been carried out, and all of them gave similar results. In China, subjects were less likely to support birth control policies after being reminded of death; in America and Israel, such reminders increased the willingness of young ladies to engage in "risky" sexual relationships with the danger of becoming pregnant.

Psychologists from the University of Oklahoma decided to test whether the reminder of death affects women's preferences when evaluating male faces. The study involved 139 female students who do not take hormonal drugs. The subjects were randomly divided into two groups - experimental and control. Students from the first group were asked before testing to write a short essay on the topic "My feelings about my own death and what will happen to me when I die." For the control group, “death” was replaced with “the upcoming exam” in the topic of the essay. Then, in accordance with accepted methods, the students completed a small "distraction" task, so that some time passed between the reminder of death and testing. After that, the subjects were presented with sequences of faces generated by a computer - from extremely masculine to extremely feminine. It was necessary to choose from these persons "the most attractive".

It turned out that the reminder of death greatly affects women's preferences. Female students from the control group, as in all previous studies of this kind, preferred more masculine faces if they themselves were ready to conceive, and less masculine if they were in that phase of the cycle when conception is unlikely. But the students who had to write an essay about their own death, tastes changed dramatically: they liked less masculine faces in the fertile phase and more masculine in the non-fertile phase.

The authors discuss several possible interpretations of the obtained results (it is clear that many of them can be invented). One of the proposed explanations seems to be the most interesting in the light of the data on sparrows and ardipithecus described above. Perhaps the reminder of death inclines women to choose not "good genes" for their potential children, but a "caring father." The fact is that men, like sparrows, have a negative correlation between the severity of masculine traits and a tendency to take care of their wife and children. In addition, men with the most masculine faces, on average, are less prone to pro-social (socially useful) behavior and adherence to social norms. They are more aggressive, and therefore life with them is fraught with a certain risk. Probably, thoughts about the inevitability of death can act on women in much the same way as on sparrows - awareness of one's own weakness. Both encourage females to bet not on "good genes", but on a potentially more caring father ( Vaughn et al. 2010). Perhaps the burdened with children, omnivorous, eternally hungry Ardi sisters felt the same way?

Lovejoy's model is the "adaptive complex" of early hominids. The arrows between the rectangles indicate causal relationships, the arrows inside the rectangles indicate an increase or decrease in the corresponding indicators. In the last common ancestor of humans and chimpanzees, the collectives probably consisted of many males and females interbreeding relatively freely with each other. They had moderate polymorphism in canine size and low levels of aggression between males; there were sperm wars. Early hominins developed three unique traits (dark triangles), two of which are documented in the fossil record (bipedalism and reduced fangs). Suggested causal relationships: 1) the need to carry food led to the development of bipedalism; 2) the choice of non-aggressive partners by females leads to a decrease in fangs; 3) the need to protect themselves from "adultery" (in both sexes) leads to the development of latent ovulation. This course of evolution is generated by two groups of factors: the food strategy of early hominids (left column) and the "demographic dilemma" caused by the intensification of the K-strategy (right column). The selection pressure caused by these factors leads to the development of the "sex for food" strategy. The subsequent increase in male height and efficient male-to-male cooperation in Australopithecus afarensis ensured the effectiveness of collective foraging raids. This made it possible in the future to master the prey of carrion in the savannah, and then collective hunting (genus Homo). Such an "economic revolution" contributed to the improvement of adaptations to bipedal walking, further strengthening of intra-group cooperation and reduction of intra-group aggression, an increase in the amount of energy that could be devoted to raising offspring, and an increase in the birth rate and survival of children. It also loosened the restrictions that hinder the development of "expensive" tissues (the brain). Based on a drawing from Lovejoy, 2009.

As a result of the events described, our ancestors formed a society with a reduced level of intragroup aggression. It is possible that intergroup aggression also decreased, because with the way of life that Ardipithecus supposedly led, it is difficult to assume developed territorial behavior. The uneven distribution of resources across the territory, the need to travel long distances in search of valuable food objects, the high risk of a predator getting for dinner - all this made it difficult (although not completely excluded) the existence of clear boundaries between groups and their protection.

The decrease in intra-group aggression created the prerequisites for the development of cooperation and mutual assistance. The reduction in antagonism between females allowed them to cooperate in joint care of the young. The decrease in antagonism between males made it easier to organize joint raids for food. Chimpanzees also occasionally practice collective hunting, as well as collective fighting against neighboring groups of chimpanzees. In early hominids, this behavior probably developed much more.

This opened up new ecological possibilities for the hominids. Valuable food resources that are impossible or extremely dangerous to obtain alone (or in small, poorly organized, ready to scatter groups at any moment) suddenly became available when male hominid learned to unite in close-knit squads, where everyone could rely on a comrade.

It is not difficult to deduce from this the subsequent development of completely new types of resources by the descendants of Ardipithecus - including the transition to feeding on carrion in the savannah (this was undoubtedly a very risky business requiring a high level of male cooperation; see below), and then to collective hunting for large game.

The subsequent expansion of the brain and the development of the stone industry appears in Lovejoy's model as a by-product - and even to a certain extent accidental - consequence of the direction of specialization in which the early hominids took. The ancestors of chimpanzees and gorillas had the same initial capabilities, but they were "led" along a different evolutionary route: they relied on the forceful solution of matrimonial problems, and therefore the level of intra-group antagonism remained high, and the level of cooperation remained low. Complex tasks, the solution of which requires coordinated actions of close-knit and friendly teams, remained inaccessible to them, and as a result, these monkeys did not become intelligent. The hominids "chosen" a non-standard solution - monogamy, a rather rare strategy among mammals, and this ultimately led them to the development of the mind.

Lovejoy's model ties together three unique hominid features: bipedalism, small fangs, and hidden ovulation. Its main advantage lies precisely in the fact that it gives a single explanation for these three features, and does not look for separate reasons for each of them.

Lovejoy's model has been around for 30 years. All its components have long been the subject of lively discussion in the scientific literature. Lovejoy draws on a wealth of facts and theory, not just the meager information and rudimentary reasoning that can be presented in a popular book. The new data on Ardipithecus fit extremely well into Lovejoy's theory and made it possible to refine its details. Lovejoy is well aware that his model is speculative and some of its aspects will not be easy to confirm or refute ( Lovejoy 2009). Nevertheless, it is, in my opinion, a good theory, consistent with most of the known facts. It can be hoped that subsequent anthropological discoveries will gradually make some of its provisions generally recognized.

Back to the childhood?

We said above that the reduction of canines in male early hominids can be considered as "feminization". Indeed, the reduction of one of the characteristic "male" simian traits made male hominids more like females. Perhaps this was due to a decrease in the production of male sex hormones or a decrease in the sensitivity of certain tissues to these hormones.

Look at the zoo for orangutans and gorillas. The Moscow Zoo, for example, now has one gorilla and two orangutan families. They live in spacious enclosures, they feel good there, and you can watch them for hours, which is what I sometimes do. It doesn't take a biologist to notice how much more human-like the females of these two species are than the males. A mature male orangutan or gorilla looks creepy, he is all hung with secondary sexual characteristics that demonstrate masculinity and strength: a humpbacked silvery back, a brutal look, inconceivable pancake-shaped cheeks, huge folds of black skin on his chest. There is little human in them. But the girls are pretty cute. Perhaps you won’t take such a wife, but so, take a walk, sit in a cafe, chat about this and that ...

In addition to feminization, there was another important trend in the evolution of our ancestors. In terms of the shape of the skull, the structure of the hairline, the size of the jaws and teeth, a person is more like baby monkeys than adults. Many of us retain long-term curiosity and playfulness, traits that most mammals have only in childhood, while adults are usually sullen and incurious. Therefore, some anthropologists believe that neoteny, or juvenilization, a delay in the development of certain traits, leading to the preservation of childish features in adult animals, played an important role in human evolution.

We can also talk about a broader concept - heterochrony. This is the name of any changes in the speed and sequence of the formation of different signs in the course of development (neoteny is a special case of heterochrony). For example, according to one theory, an important role in human evolution was played by the accelerated development of socially oriented mental abilities (see the chapter "The Public Brain", book 2).

Juvenilization could also contribute to the transition to monogamy. Indeed, in order for couples to become at least somewhat stable, partners must have special feelings for each other, mutual affection must form between them. In evolution, new traits rarely arise from nothing; usually some old trait is used, which, under the influence of selection, undergoes a certain modification. The most suitable "blank" (pre-adaptation) for the formation of stable marital attachment is the emotional connection between mother and child. The study of mono- and polygamous species of rodents suggests that the system for the formation of strong family ties has repeatedly developed in the course of evolution precisely on the basis of an older system for the formation of an emotional bond between a mother and her offspring (see the chapter "Genetics of the Soul", book 2).

Something similar may have happened in the relatively recent history of mankind, about 10-15 thousand years ago, when our ancestors began to domesticate wild animals.

In 2006, Emanuela Prato-Previde and her colleagues at the Milan Institute of Psychology conducted a series of observations on the behavior of dogs and their owners under unusual, stressful conditions. First, each couple (the dog and its owner) were placed in a half-empty room with a strange setting consisting of a couple of chairs, a cup of water, an empty plastic bottle, two balls, a toy on a string, a squeaker toy, and a video camera that recorded everything that happened. Then the owner was taken to the next room, where he could observe the suffering of the dog left alone on the monitor. After a short separation, the owner was allowed back. Then followed a second, longer separation and a new happy reunion.

The people participating in the experiment (among them 15 women and 10 men) were told by cunning psychologists that they were interested in the behavior of the dog, and asked to behave as naturally as possible. In fact, the object of the study were not dogs, but their owners. Each action of the test subjects was carefully recorded and classified. The exact number of strokes, hugs, kisses, play actions, and so on was counted. Particular attention was paid to spoken words.

It turned out that both men and women, in communicating with a four-legged friend, used many of the behavioral elements that are characteristic of parents communicating with young children. Particularly revealing were the subjects' speeches, which abounded in repetitions, diminutive forms of words, affectionate names, and other characteristic features of the so-called maternal language. After a long separation (accompanied by more severe stress both for the "abandoned" dog and for the owner who was watching her experiences), the play activity of the subjects decreased markedly, but the number of hugs and other lisping increased. Men chatted with their dogs somewhat less than women, but this could be due to the fact that men are more sensitive to the presence of a video camera: perhaps they were afraid of appearing funny when talking to a dog. There were no other significant differences in the behavior of men and women.

In this purely observational-descriptive study, there was no control, no big statistics, no artificial viruses were injected into the brain of anyone, no genes were turned off, and no jellyfish green fluorescent protein was made to glow. Nevertheless, the authors believe that their results are a strong argument in favor of the hypothesis that canine-human symbiosis was originally built on the transfer of the parental stereotype of behavior to new four-legged friends ( Prato-Previde et al., 2006). This hypothesis is supported by other facts. For example, in some traditional cultures, untouched by civilization, it is customary to keep a lot of completely useless pets, and in many cases they are treated exactly like children, women even breastfeed them ( Serpell, 1986). Maybe the first wolf cubs that settled in the dwelling of a Paleolithic man did not perform any utilitarian functions and our ancestors sheltered them not to help in hunting, guarding a cave or eating leftovers, but only for spiritual comfort, for friendship, for mutual understanding? Romantic, but quite respected by many psychologists hypothesis.

The ability to transfer to other social partners the behavior developed for communication with children could play an important role in human evolution. It is possible that the juvenile appearance and behavior of adult hominids was supported by selection, because such individuals, slightly similar to children, their marriage partners experienced more tender feelings. This could increase their reproductive success if wives were less likely to cheat on such husbands (who were also likely to be less aggressive and more reliable), and husbands were less likely to leave girl wives, whose whole appearance spoke of how needy they were. in protection and support. So far, this is just fortune-telling on the coffee grounds, but nevertheless, some indirect arguments in favor of this guess can be made.

If juvenilization really took place in the evolution of human thinking and behavior, then something similar could very well be in the evolution of our closest relatives - chimpanzees and bonobos. These two species differ markedly in their character, behavior and social structure. Chimpanzees are quite gloomy, aggressive and warlike, in their groups males are usually in charge. Bonobos live in more abundant places than chimpanzees. Perhaps that is why they are more carefree and good-natured, easier to put up with, their females are better at cooperating and have more "political weight" in the team. In addition, in the structure of the bonobo skull, like in humans, there are signs of juvenile development. Perhaps such signs can be found in the behavior of bonobos?

Recently, American anthropologists from Harvard University and Duke University decided to check whether chimpanzees and bonobos differ in the chronology of the development of certain features of thinking and behavior associated with social life ( Wobber et al., 2010). To do this, three series of experiments were carried out with chimpanzees and bonobos leading a semi-wild (or "semi-free") lifestyle in special "shelters", one of which is located on the northern coast of the Congo (chimpanzees live there), the other - on the south, in the bonobo estate . Most of these monkeys were confiscated from poachers at an early age, and only a few were born in the shelter.

In the first series of experiments, the monkeys were let in pairs into a room where there was something tasty. The division into pairs was carried out so that in each pair there were monkeys of approximately the same age and that there was an approximately equal number of same-sex and opposite-sex pairs. Three types of treats were used, differing in the ease of "monopolization" (some were easier to completely appropriate for oneself, others were more difficult). The researchers kept an eye on whether the monkeys would eat together or if one of them would grab everything. In addition, cases of gaming and sexual behavior were recorded.

It turned out that young chimpanzees and bonobos are equally willing to share food with their comrades. With age, however, chimpanzees become more greedy, while bonobos do not. Thus, bonobos retain in adulthood a "childish" trait - the absence of greed.

Bonobos were more likely than chimpanzees to play games in this experiment, including sexual ones. In both species, playfulness declined with age, but it happened faster in chimpanzees than in bonobos. Thus, in this regard, bonobos also behave "childishly" when compared with chimpanzees.

In a second set of experiments, the monkeys were tested for their ability to refrain from mindless activities in a specific social context. Three people were placed shoulder to shoulder in front of the monkey. The two outermost people took treats from a container inaccessible to the monkey, while the middle one did not take anything. Then all three extended their hand to the monkey, clenched into a fist, so that it was not clear who had an empty fist, and who had a treat. The monkey could ask for food from each of the three. It was believed that the monkey solved the problem correctly if it asked only the two outermost ones, who took a treat from the container before her eyes, and did not ask the middle one.

Chimpanzees, as it turned out, already at the age of three perfectly cope with this task and retain this skill for life. Smaller bonobos, on the other hand, often make the mistake of asking all three of them for food. Only by the age of 5-6 years do bonobos catch up with chimpanzees in terms of the frequency of correct decisions. Thus, in this case, too, one can speak of a delay in the mental development of bonobos compared to chimpanzees. Of course, we are not talking about mental retardation. Bonobos aren't dumber than chimpanzees, they're just more carefree and less socially harsh.

In the third series of experiments, the monkeys were given a more difficult task - to adapt to a change in human behavior. It was necessary to ask for food from one of the two experimenters. During the preliminary tests, one of the two always gave the monkey a treat, and the other never. The monkey, of course, got used to this and began to choose a "good" experimenter over and over again. Then the roles suddenly changed: the kind experimenter became greedy, and vice versa. Scientists monitored how quickly the monkey would understand what had happened and change its behavior in accordance with the changed situation. The results were approximately the same as in the previous series of experiments. Starting at the age of five, chimpanzees quickly retrained and began to choose the experimenter who treated them now, and not in the past. Young bonobos coped with the task worse and caught up with chimpanzees only by 10-12 years.

These results are in good agreement with the hypotheses about the important role of heterochrony in the evolution of thinking of higher primates and that bonobos are characterized by a delay in the development (juvenilization) of some mental traits compared to chimpanzees. It is possible that the primary reason for the differences found is the reduced level of intraspecific aggression in bonobos. This, in turn, may be due to the fact that bonobos live in more abundant areas, and they have less competition for food.

The authors draw attention to the fact that artificial selection for reduced aggressiveness during domestication in some mammals led to the juvenileization of a number of traits. In particular, they mention the famous experiments of D.K. Belyaev and his colleagues on the domestication of foxes ( Trut, 2007). In these experiments, foxes were selected for reduced aggressiveness. The result was friendly animals that retained some of the "childish" traits in adulthood, such as lop-earedness and a shortened muzzle. It seems that selection for friendliness (in many animals this is a "childish" trait) may, as a side effect, lead to the juvenileization of some other features of morphology, thinking, and behavior. These signs can be interconnected - for example, through hormonal regulation.

So far, we cannot say for sure how relevant the selection for reduced aggressiveness was in our ancestors and whether our juvenile features (high forehead, shortened facial part of the skull, character of the hairline, curiosity) can be explained by such selection. But the suggestion looks tempting. Apparently, the decrease in intragroup aggression played an important role in the early stages of hominin evolution. But there are also many facts indirectly pointing, on the contrary, to the growth of hostility between groups of hunter-gatherers (moreover, this is considered as one of the reasons for the development of intra-group cooperation; we will return to this topic in the chapter "The Evolution of Altruism", Book 2). But in this case we are already talking about the later stages of evolution and about intergroup aggression. So these hypotheses do not contradict each other.

australopithecines

Let's get back to history. If a long series of lyrical digressions did not confuse the reader, then he still remembers that we settled on the Ardipithecus, who lived in East Africa 4.4 million years ago. Shortly thereafter, about 4.2 million years ago, Ardi's successors enter the African scene - slightly more "advanced", slightly more "human" bipedal monkeys, united by most anthropologists in the genus Australopithecus. The oldest known species of this genus, Australopithecus anamus ( Australopithecus anamensis, 4.2–3.9 Ma) is described from fragmentary material. Therefore, it is difficult to say anything definite about him, except that his structure was really intermediate between the Ardipithecus and the later - and better studied - Australopithecus. He could very well be a descendant of Ardi and an ancestor of Lucy.

Afar Australopithecus, the species to which Lucy belonged, lived in East Africa from about 4.0 to 2.9 million years ago. The remains of many individuals of this species have been found. A. afarensis almost certainly was among our ancestors, or at least was very closely related to them. Primitive features (for example, a brain with a volume of only 375-430 cm 2, like a chimpanzee) were combined with advanced, “human” ones (for example, the structure of the pelvis and lower limbs, indicating upright posture).

About Lucy, described in 1978 by Donald Johanson, Tim White and Yves Koppen, Johanson himself spoke in detail in the book "Lucy: the origins of the human race." This book was published in Russian in 1984. We will confine ourselves to a brief account of two new important finds.

The search for fossil remains of hominids in East Africa - the cradle of mankind - has long ceased to be the lot of lone enthusiasts. The work is on a grand scale, promising areas are divided among competing groups of anthropologists, excavations are carried out systematically and very purposefully. In 2000, in one of these "research areas" - in Dikik (Ethiopia) - a unique find was made: a well-preserved skeleton of a young Afar Australopithecus, most likely a three-year-old girl, who lived 3.3 million years ago. Anthropologists gave her the unofficial nickname "Lucy's daughter" ( Alemseged et al. 2006; Wynn et al., 2006). Most of the bones were walled up in hard sandstone, and it took five whole years to prepare the skeleton (cleaning the bones from the host rock).

The Dikik region, and in particular those layers in which the skeleton was found, have been thoroughly studied in paleontological terms, which made it possible to reconstruct the habitat of "Lucy's daughter". It looks like it was a paradise place: a river valley with lush floodplain vegetation, lakes, a mosaic landscape with alternating forest areas and open spaces, an abundance of herbivores, including large ones, characteristic of both forest and steppe habitats (antelopes, rhinos, hippos , fossil three-toed hipparion horses, many elephants), and almost complete - as far as can be judged from the fossil remains - the absence of predators (only numerous bones of a large fossil otter were found Enhydriodon and a lower jaw, possibly from a raccoon dog). In general, there was less forest and more savannah here than in the habitats of older hominids - Ardipithecus, Australopithecus Anam and Kenyanthropus.

Australopithecus afarensis is one of the most well-studied hominin species. Its remains have been found in numerous places in Ethiopia, Kenya and Tanzania. At the Hadar site in central Ethiopia alone, the bones of at least 35 individuals have been found. However, before the “daughter Lucy” was found and dissected, scientists knew almost nothing about how these monkeys developed and what their children looked like.

The geological age of the find (3.31–3.35 Ma) was determined by the stratigraphic method [Stratigraphy is the science of dividing sedimentary rock strata into layers, determining their relative geological age (as a rule, young layers lie on top of older ones) and the correlation (correlation with each other) of the same age layers from different places and sedimentary strata. Many methods are used to correlate layers, including paleontological (comparison of complexes of fossil remains of living organisms)]. This means that, according to a complex of paleontological and other features, the rock in which the skeleton was found was attributed to a strictly defined stratigraphic horizon (layer), the absolute age of which was previously established using several independent radiometric methods. [For more information about methods for determining the age of rocks and fossils contained in them, see: Markov A.V. Chronology of the distant past].

The individual age of the girl herself (about three years old) was determined by her teeth. In addition to well-preserved milk teeth, computed tomography revealed developing adult teeth in the jaws. Their shape and relative size also made it possible to determine the sex of the child (it is known that in Afar australopithecines, men and women differed from each other in a number of ways, including teeth, more strongly than in later hominids).

The authors of the find compared it with another young australopithecine, the "child from Taung", found in the 1920s in South Africa by Raymond Dart (this was the beginning of the study of australopithecines). The "Child from Taung" lived much later and belonged to a different species - Australopithecus africanus. It turned out that the girl from Dikiki, despite her young age, already had a number of characteristic distinguishing features of her species. A. afarensis, so that its species affiliation is beyond doubt.

The brain volume of the girl is estimated at 275–330 cm3. This is slightly less than what would be expected from the average brain size of adult Australopithecus. Perhaps this indicates a somewhat slower brain growth compared to modern humanoids. Very rarely preserved in fossil hominids, the hyoid bone is similar to that of young gorillas and chimpanzees and is very different from humans and orangutans. This is an argument in favor of the absence of speech in Australopithecus, which, however, did not raise much doubt anyway. [The question of the origin of speech in hominids is discussed in detail in the book by S. A. Burlak "The Origin of Language" (2011), so we almost do not touch on this topic here].

The girl's legs, like those of other Afar australopithecines, have many advanced ("human") features. This once again confirms that A. afarensis was an upright creature. The bones of the arms and shoulder girdle, according to the authors, bring the young Australopithecus closer to a gorilla than to a man, although some shift towards the "human" side is still observed.

In general, the find confirmed the "functional dichotomy" in the structure of the Afar australopithecines: a very advanced, almost human lower body was combined with a relatively primitive, "monkey" upper part. This "monkey top" was interpreted by some researchers simply as the legacy of their ancestors, from which the Australopithecus had not yet had time to get rid of, others as evidence of a semi-arboreal way of life. However, both interpretations may well be true at the same time.

Lucy's daughter's shoulder blade - the first intact shoulder blade found A. afarensis- only confused the matter more, since it resembles a gorilla's shoulder blade (more precisely, it looks like something intermediate between a gorilla and human shoulder blades), and gorillas are not the biggest tree climbers. They actively use their hands when walking, relying on the knuckles, like chimpanzees. The authors who described Lucy's daughter are still inclined to believe that the Afar australopithecines spent a lot of time in trees and therefore retained adaptations for climbing.

Various combinations of primitive and advanced traits are generally very characteristic of fossil organisms, whose primitiveness and advancedness we evaluate retrospectively - by comparison with distant descendants and ancestors. Evolutionary changes of different organs and parts of the body always go at different speeds - there is simply no reason why they should all change absolutely synchronously. Therefore, no matter what transitional form we take, it will always turn out that some signs of it are already “almost like a descendant”, while others are still “quite like an ancestor”.

Young Australopithecus were the prey of birds of prey

Australopithecus Africanus ( Australopithecus africanus) lived in South Africa between 3.3–3.0 and 2.4 mya. It was from this species that the study of Australopithecus began.

The famous skull of the "Taung Child" was found by a miner in a lime mine in South Africa in 1924. The skull fell into the hands of Raymond Dart, one of the pioneers of paleoanthropology. The following year, a sensational article by Dart appeared in the journal Nature, entitled "Australopithecine africanus: a man-ape from South Africa" ​​( Dart, 1925). So for the first time mankind learned about Australopithecus - the long-awaited "missing link" between the monkeys and the Pithecanthropes already known by that time ( Homo erectus).

Together with the skull of a young Australopithecus, bones of baboons, antelopes, turtles and other animals were found in the Taung cave. The skulls of the baboons seemed to have been smashed through by some kind of blunt instrument. Dart suggested that all this fauna is the remains of the feasts of the apes. This is how the image of Australopithecus arose - a skilled hunter who ran across the savannah after baboons and killed them with a blow to the head with a club. Subsequently, adults were found A. africanus, also in a complex with a diverse fossil fauna.

A detailed study of these paleocomplexes led scientists to the conclusion that the found clusters of bones are indeed the remains of feasts, but not of apes, but of some other predators. Australopithecus were not hunters, but victims. Suspicion first fell on large felines such as the sabertooth megantereon ( Meganterion). The leopard and the spotted hyena were also named among the possible hunters of the apes. These assumptions were based, in particular, on a comparison of the trace element and isotope composition of the bones of predators and ancient hominids, as well as on the characteristic lesions on the bones of the latter, exactly corresponding to the fangs of a leopard.

In 1995, it was first suggested that the "child from Taung", along with baboons and other animals, fell victim to a large bird of prey, similar to the modern African crowned eagle ( Berger, Clarke, 1995). The hypothesis has been heavily criticized. In particular, the opinion was expressed that not a single eagle is able to lift into the air such a large prey as an Australopithecus cub.

In recent years, much more has become known about the habits of large birds of prey - monkey hunters. For example, it turned out that the lifting power of these birds was still greatly underestimated. However, the "bird hypothesis" lacked decisive evidence - clear evidence that the "child from Taung" had been in the claws of a huge eagle. Such evidence was obtained in 2006, after the skulls of modern monkeys killed by a crowned eagle were examined in detail. Having become acquainted with the new data, the South African anthropologist Lee Berger, one of the authors of the "bird hypothesis", drew attention to the description of the characteristic holes and breaks in the upper parts of the eye sockets left by eagle claws. The scientist immediately re-examined the skull of the "child from Taung" and found the same damage in both eye sockets.

Nobody paid attention to them, which is not surprising - after all, until now, these injuries still could not be interpreted. In the right eye socket of the "child from Taung" there is a noticeable round hole with a diameter of 1.5 mm, in the upper part of the left eye socket there is a large gap with uneven edges. Together with the dent on the top of the skull described back in 1995, these injuries are sufficient evidence that the young Australopithecus was caught, killed and eaten by a large bird of prey.

Berger points out that eagles were most likely far from the only enemies of Australopithecus. Quadrupedal and feathered predators are the most important factor in mortality among modern African monkeys, and, apparently, things were no better for our distant ancestors. Many anthropologists consider the threat from predatory animals and birds to be one of the important reasons for the development of sociality among ancient hominids (and high sociality, in turn, could contribute to the accelerated development of the mind), therefore, in order to understand the evolution of our ancestors, it is important to know who hunted them ( Berger, 2006).

The point of view about the semi-arboreal life of the Afar australopithecines, as well as their not quite human, clumsy gait, has recently been disputed by many anthropologists. Against it are new data obtained during the study of the famous tracks from Laetoli (Tanzania), as well as the recent discovery of the postcranial skeleton of a very large representative A. afarensis- Big man.

The traces of Laetoli were discovered by Mary Leakey in 1978. This is a chain of traces of three hominids, imprinted in ancient volcanic ash: two adults and one child. The oldest traces of bipedal primates glorified not only Mary Leakey herself, but also the place of the find - the village of Laetoli, located in East Africa, in Tanzania, in the Ngorongoro Reserve. On the edge of the Serengeti plateau, not far from Laetoli, is the now extinct volcano Sadiman - it was his ashes that immortalized the traces of Australopithecus.

The volcanic eruption that the three may have been trying to escape from happened 3.6 million years ago. In those parts of the hominids known to science, then only the Afar Australopithecus lived. Most likely, they left traces. From the prints of the feet it is clear that their thumb was no longer opposed to all the others, like Ardi's, but was adjacent to them - almost like ours. So, the Afar Australopithecus said goodbye to the old monkey custom of grabbing branches with their feet.

But how did they walk anyway - clumsily hobbled on half-bent, like modern gorillas or bonobos, when it is a whim for them to walk "without hands", or with a confident, firm gait, straightening their legs - like a human being? Recently, American anthropologists have taken up this issue in earnest ( Raichlen et al., 2010). They forced human volunteers to walk in different gaits on the sand, distributing their body weight in different ways and placing their feet in different ways, and then compared the resulting footprints with the footprints from Laetoli. Conclusion: the gait of the Afar australopithecines practically did not differ from ours. They walked confidently and moved their legs like us, fully straightening their knees.

A large Afar australopithecine, nicknamed Kadanuumuu (which means big man in the local dialect), was described in 2010 by a group of anthropologists from the United States and Ethiopia ( Haile-Selassie et al., 2010). Owen Lovejoy, already known to us, was part of the research team. The find was made in the Afar region of Ethiopia, the same place where many other fossil hominids come from. The skull was never found, but the bones of the left leg and right hand (without foot and hand), a significant part of the pelvis, five ribs, several vertebrae, the left collarbone and right shoulder blade were found. Most likely, it was a male (or is it time to say - a man?), And a very large one. If Lucy's height was about 1.1 m, then the Big Man was about half a meter taller, that is, his height was within the normal range of modern people. He lived 3.6 million years ago - 400,000 years earlier than Lucy and almost simultaneously with three unknowns who left traces on volcanic ash in Laetoli.

The structure of the skeleton of the Big Man, according to the authors, indicates a high adaptability to full-fledged bipedal walking and the absence of adaptations for tree climbing. Kadanuumuu's shoulder blade is much less gorilla-like than Lucy's daughter's shoulder blade, and looks almost human. From this the authors conclude that the Big Man knew how to climb trees a little better than we do. The ribs, pelvis, and limb bones also show many advanced features. Even the ratio of the length of the arms and legs, although with difficulty, fits into the range of normal variability Homo sapiens. Among modern people, there are few such long-armed and short-legged individuals, but still they come across. Apparently, this means that the Afar australopithecines were quite variable in size and proportions of their body - perhaps almost the same as modern people. Characteristics that were previously conventionally considered to be inherent in all Afar people (for example, very short legs, like Lucy's), in fact, could depend on age, sex, and vary widely within the population.

As for sexual dimorphism (differences in body size and proportions between men and women), there is fierce debate about this. Some authors (perhaps the majority) believe that dimorphism in Afar australopithecines was much more pronounced than in modern humans. In monkeys, strong sexual dimorphism (when males are much larger than females) is a sure sign of a harem system, which would seem to contradict the supposed monogamy of Australopithecus. Other authors, including Lovejoy, argue that the sexual dimorphism of the Afar people was about the same as ours. Of course, the discussion is not based on reasoning, but on real bones and careful measurements, but the collected material, apparently, is still not enough for reliable conclusions.

According to the anthropologist S.V. Drobyshevsky (2010, who studied a large number of endocranes (casts of the brain cavity) of fossil hominids, the brain of Australopithecus was similar in structure to the brain of chimpanzees, gorillas and orangutans, but differed in a more elongated shape due to an enlarged parietal lobe. Perhaps, this was due to the fact that australopithecines had greater mobility and sensitivity in their hands, which is actually logical, given their walking style.

paranthropes

Paranthropus, also called massive australopithecines, is one of the dead-end branches on the evolutionary tree of hominids. Three types of Paranthropus have been described: P. aethiopicus(2.6–2.3 Ma, East Africa), R. boisei, also known as Zinjanthropus (2.3–1.2 million years ago, East Africa), and R. robustus(1.9–1.2 Ma, South Africa). They lived simultaneously with other representatives of hominids - ordinary, or gracile (more miniature), australopithecines, such as A. garhi from East Africa and South African A. sediba, and the most ancient representatives of the human race ( Homo).

In the initial period of their history, representatives of the human race lived in Africa, surrounded by a variety of relatives who differed from ancient people much less than modern chimpanzees differ from modern humans. Interspecies relationships within the hominin group undoubtedly left their mark on the early stages of human evolution. The presence of several closely related species in the same area probably required the development of special adaptations to prevent interspecific hybridization and to separate ecological niches (it is difficult for closely related species to get along together if their diets and lifestyles are the same). Therefore, in order to understand the early stages of the history of the genus Homo it is important to know how our extinct bipedal cousins ​​lived and ate—even if we know they were not our ancestors.

The Paranthropes appear to have evolved from the common, or gracile, Australopithecus (like the first humans), but their evolution went the other way. First Homo included in their diet the remains of the meals of predators and learned to scrape off the remains of meat and split bones with primitive stone tools; their brains began to increase, while their jaws and teeth, on the contrary, gradually decreased. Paranthropus went the other way: their brains remained small (roughly like those of chimpanzees and gracile australopithecines), but the teeth, jaws and chewing muscles reached an unprecedented level of development for hominids. The fangs, however, remained relatively small: it was probably already irreversible.

It has traditionally been thought that the driving force behind these changes was an adaptation to a diet of coarse plant foods—tough roots, stems, leaves, or hard-shelled nuts. Based on morphological data, scientists reasonably believed that Paranthropus were specialized consumers of the toughest and hardest food objects, inaccessible to other hominids due to the relative weakness of their jaws and teeth. It was also assumed that a narrow food specialization may have been one of the reasons for the extinction of Paranthropus. The first people, on the contrary, retained the omnivorous nature of their ancestors, the gracile australopithecines. It is clear that omnivorous forms are more likely to survive a change in the environment than narrow specialists. History repeated itself in more recent times, when a highly specialized species of people who ate mainly meat - Neanderthals - was supplanted by an omnivore. Homo sapiens [Only at the end of 2010 did it become clear that neither Asian nor European Neanderthals were in fact 100% meat-eaters, as would seem to follow from the isotopic composition of tooth enamel. Starch granules have been found in the tartar of Neanderthals, indicating that from time to time they ate barley, dates, legumes (in Asia), rhizomes of water lilies, and possibly cereals (in Europe). Moreover, judging by the shape of these pellets, Neanderthals even knew how to cook plant foods] (Dobrovolskaya, 2005).

Subsequently, facts were discovered that contradicted the hypothesis of a narrow food specialization of Paranthropus. Analysis of the isotopic composition of tooth enamel showed that they were apparently omnivores ( Lee-Thorp et al., 2000). In particular, termites were included in their diet, which Paranthropus mined using primitive bone tools ( d "Errico, Backwell, 2009).

But the opinion remained unshakable that coarse plant food was an important part of the paranthropus diet. Otherwise, why do they need such powerful jaws and huge teeth? However, in 2008 this seemingly self-evident assumption was called into question ( Ungar et al., 2008).

American anthropologists studied the microscopic traces of tooth enamel wear preserved on the molars of seven individuals. Paranthropus boisei. This species lived in the East African savanna, often near rivers and lakes. Specialization features characteristic of paranthropes (large flat molars, thick tooth enamel, powerful chewing muscles) are most pronounced in this species. Not surprisingly, the first found skull of this species was nicknamed the Nutcracker. Of the 53 studied individuals, the details of the structure of the tooth surface were well preserved only in seven. However, these seven individuals are quite a representative sample. They come from three countries (Ethiopia, Kenya, Tanzania) and cover most of the existence of this species. The oldest of the skulls is about 2.27 million years old, the youngest is 1.4 million years old.

The authors used two characteristics of the enamel surface, reflecting the nature of food preferences: fractal complexity (a variety of sizes of microscopic depressions and grooves) and anisotropy (the ratio of parallel and randomly oriented microscratches). A study of the teeth of modern primates on various diets has shown that high fractal complexity is associated with feeding on very hard foods (such as cracking nuts), while high anisotropy reflects feeding on hard foods (roots, stems, leaves). It is important that traces of microwear of tooth enamel are ephemeral - they do not accumulate during life, but appear and disappear in a few days. Thus, according to these traces, one can judge what the animal ate in the last days of its life. For comparison, the authors used the teeth of four modern primate species whose diet includes hard and rigid objects, as well as two fossil hominids: Australopithecus africanus and Paranthropus robustus.

The results surprised the researchers. Scratching of tooth enamel R. boisei turned out to be very low. No signs of feeding on particularly hard or rigid objects could be found. Modern solid-feeding monkeys have markedly higher fractal complexity scores, while hard-food primates have higher anisotropy scores.

Nutcrackers rarely seem to have gnawed on nuts or chewed on tough vegetation. They preferred something softer and more nutritious, like juicy fruits or insects. At least none of the seven individuals studied ate anything hard or tough in the last days before death. The surface texture of their tooth enamel is similar to that of soft fruit-eating monkeys.

Previously, a similar analysis was carried out for another species of Paranthropus - the South African R. robustus. It turned out that this species also ate hard and rigid objects not always - apparently, only at certain times of the year ( Scott et al., 2005). It's amazing that P. boisei whose teeth and jaws are more developed than those of R. robustus ate solid food less frequently. He seemed to eat more hard food than R. robustus, but not more often than the gracile australopithecine Australopithecus africanus, which did not have such powerful teeth and jaws as those of Paranthropus.

It turns out that paranthropes preferred to eat something completely different from what their teeth and jaws were adapted to. This seems paradoxical - and indeed, this phenomenon is known to science as Liam's paradox. The discrepancy between morphological adaptations and real food preferences is sometimes found, for example, in fish, and the reasons for this phenomenon are now generally understood ( Robinson, Wilson, 1998). This happens when the preferred types of food are easily digestible and do not require the development of special adaptations, but sometimes the "good" food is not enough, and then the animals have to switch to another, less quality or poorly digestible food. During such critical periods, survival will depend on the ability to effectively obtain and assimilate "bad" food - one that the animal under normal conditions will not come close to. Therefore, there is nothing unnatural in the fact that some animals have developed morphological adaptations to feeding on food that they usually do not eat. Something similar is observed in some modern primates - for example, in gorillas, which prefer fruits, but in times of famine they switch to tough leaves and shoots.

Perhaps paranthropes are one example of Liam's paradox. Soft fruits or insects can be eaten by hominids with any teeth and jaws, but chewing hard roots during periods of hunger requires large teeth and powerful jaws. Even if such hunger strikes are rare, it is enough for natural selection to favor stronger teeth and jaws.

Most likely, there was some sexual selection here - especially if you take into account the latest data that paranthropes had highly developed sexual dimorphism, males were much larger than females and had harems (see below). Powerful jaws and teeth could increase the chances of a male to win in competition with other males and increase their attractiveness in the eyes of females. Our ancestors obviously had different tastes. They were attracted to males by something else - perhaps caring, the ability to get a tasty marrow bone for their beloved from under the noses of hyenas and vultures, complex and inventive behavior during courtship?

Thus, not only were paranthropes not food specialists, they may have been even more omnivorous than gracile australopithecines. After all, the latter, it seems, could not eat the hard parts of plants, but paranthropes could, although they did not like it. On the other hand, all the food resources available to gracile australopithecines were also available to paranthropes. If food specialization increases the likelihood of extinction, then one would rather expect Paranthropus to survive and the line of gracile australopithecines to be extinguished. This did not happen, probably only because the descendants of the gracile australopithecines - the first people - found another, more versatile and promising way to expand their diet. Instead of powerful teeth and jaws, sharp stones, complex behavior and a smart head were used, instead of hard and inedible roots - the meat and bone marrow of dead animals.

The results obtained, among other things, show that the structure of the teeth and jaws alone cannot be used to judge with certainty the diet of extinct animals. Morphological adaptations may sometimes reflect not a preferred diet, but diets that an animal normally tries its best to avoid.

In recent years, scientists have managed to find out something about the social life of Paranthropus. Anthropologists from South Africa, the UK and Italy have come up with a new method of comparing fossil bones to help understand how male and female extinct hominids developed after they reached puberty. The fact is that in modern primates practicing a harem type of family relationships (for example, gorillas and baboons), females, having reached maturity, hardly grow anymore, while males continue to grow for quite a long time. This is due to the fact that in such species there is very strong competition between males for the right to access the team of females. Young males have almost no chance of success in the fight against seasoned individuals, so they postpone decisive action until they are in full force.

In harem species, mature males are much larger than both females and young mature males; often they also differ in color. In species that practice more democratic variants of family relations, such as humans and chimpanzees, sexual dimorphism is less pronounced (males do not differ so much from females in size and color), and in males, the achievement of sexual and social maturity approximately coincides in time. In this case, the period of "additional" growth of sexually mature males is reduced or not expressed.

The researchers reasoned that if they compared the size of individuals (determined by the size of the bones) with their age (determined by the wear of the teeth), then with enough abundant material it would be possible to understand how long the growth in males of this species continued after reaching puberty. South African view Paranthropus robustus attracted the attention of researchers primarily because of the abundance of material. The authors examined fragments of the skulls of 35 individuals and selected 19 of them for their analysis.

Three selection criteria were used: 1) erupted wisdom teeth - evidence of puberty; 2) the preservation of a significant part of the facial or jaw bones, so that the size of the individual can be estimated; 3) well-preserved molars, so that age can be estimated from the wear of the enamel.

It turned out that the studied sample is divided into two unequal parts. In the first of them (four individuals), the body size did not increase with age—the stage of “additional” growth was absent. The researchers reasoned that they were females. In the second group (15 individuals), the growth was quite significant. These are most likely males. Young males differed little in size from females, while mature males were much larger. This gives reason to believe that Paranthropus had harems, and there was intense competition between males for females.

A natural question arises: why have so many more male skulls been found than female ones? The authors give an elegant answer to this, thanks to which the unequal sex ratio among the found skulls becomes an additional confirmation of the proposed theory. The fact is that the studied skulls belong mainly to those individuals that fell victim to predators. For example, the location of the bones in the Svartkrans cave, where many bone remains have been found R. robustus, is considered a classic example of a fossil complex formed as a result of the activity of predators. Many of the bones from Swartkrans bear unmistakable tooth marks.

Why did male paranthropes fall into the clutches of saber-toothed or hyenas three times more often than females? It turns out that such a picture is observed in modern "harem" primates. Females of these species always live in groups, usually under the protection of a seasoned "husband", and males, especially young ones who have not yet managed to acquire their own harem, roam alone or in small groups. This significantly increases the chances of a predator getting to dinner. For example, male baboons during a solitary life are three times more likely to become victims of predators compared to females and males living in a team.

The authors also analyzed the material on the South African gracile australopithecines ( A. africanus), which are closer to human ancestors than Paranthropus. The material on this species is not so rich, and therefore the conclusions are less reliable. However, judging by the available facts, A. africanus sexual dimorphism was much less pronounced than in Paranthropus, and females and males became victims of predators with approximately the same frequency. This is an additional argument in favor of the fact that the harem system was absent in gracile australopithecines and family relations were more equal ( Lockwood et al., 2007).

The increased mortality of young males in the harem system is unlikely to benefit the group and the species as a whole. This can be seen as one of the reasons why paranthropes ultimately lost the evolutionary competition to their closest relatives - gracile australopithecines and their descendants, people.

Human Origins

Evidence for evolutionary human origin

Option 1

1 . What was the name of a group of great apesconsisting of the earliest primates?

1) anthropoids

2) pongids

3) hominids

4) tarsiers

2 . Which monkeys are not pongids?

1) chimpanzee

2) gorilla

3) orangutan

4) capuchins

3 . Which scientist first suppressed a person into one grouppu with primates?

1) Ch. Darwin

2) J.B. Lamarck

3) K. Linnaeus

4) T. Huxley

4. What biological feature does not characterizekind of a reasonable man?

1) large brain volume

2) strong jaws

3) the predominance of the cerebral part of the skull over the facial

4) upright posture

5 . What does the australopithecine stage correspond to in evolutionhominid families?

1) archanthrope

2) paleoanthrope

3) protoanthrope
4) neoanthrope

6 . What is the name of the oldest man, fossilswhose remains were found on the island of Java?

1) protoanthrope

2) Pithecanthropus

3) paleoanthropist

4) synanthropus

7 . What modern people appeared on Earth40-30 thousand years ago and continue to live today?

1) neoanthropes

2) archanthropes

3) Neanderthals

4) paleoanthropes

8 . At what stage of the formation of man as a biologicalWhat kind of ancient people appeared - Neanderthals?1) at the stage of neoanthropes

2) at the stage of archanthropes

3) at the stage of protoanthropes

4) at the stage of paleoanthropes

9 .To what systematic group of the Mammals class does Homo sapiens belong?

1) marsupials

2) rodents

3) predatory

4) primates

10 .Which of the driving forces of human evolution has a biological nature?

1) articulate speech

2) the ability to tool activity

3) heredity

4) abstract thinking

11. The first to learn how to use fire

1) australopithecines

2) pithecanthropes

3) Neanderthals

4) Cro-Magnons

12. Which of the following is an example of a rudiment in humans?

1) excessive hairiness

2) the presence of the coccyx

3) the presence of a tail

4) additional mammary glands

13. In humans, unlike mammals

1) the upper limb consists of the shoulder, forearm and hand

2) the brush is hook-shaped, with an underdeveloped thumb

3) the lower jaw is connected to the skull movably

4) the thumb forms a right angle with respect to other fingers

14. What is the difference between Homo sapiens and animals?

1) development of the peripheral nervous system

2) the presence of two circles of blood circulation

3)developmentS-shaped spine

4) the formation of three germ layers during embryonic development

15. What trait in humans in the process of evolution arose earlier than others?

1) speech

2) consciousness

3) regular work activity

4) bipedalism

16. What does the presence of a tail in human embryos at an early stage of its development indicate?

1) about development with complete transformation

2) about the variability of organisms

3) about the origin of man from animals

4) about deviations in its development

17. Scientists refer to the group of ancient people

1) Australopithecus

2) Cro-Magnon

3) Neanderthal

4) Pithecanthropus

18. Consider the figure, which shows the fossil ancestors of the genus Man in the chronological order of their appearance on Earth. Under what number is Homo erectus depicted on it?

1)1

2)2

3)3

4)4

19.

1) the presence of teeth in the holes of the jaws

2) the ability to regulate your body temperature

3) the presence of a nervous system

4) alveolar structure of the lungs

5) laying in the embryos of the neural tube above the chord

6) the presence of an arched foot

20 used in the systematics of man, starting with the mostlarge.

1) hominids

2) primates

3) chordates

4) man

5) mammals

6) a reasonable person

21.

labor activity

B)

abstract thinking

AT)

insulation

G)

mutational variability

D)

population waves

E)

second signaling system

biological

2)

social

Human Origins (anthropogenesis). The evolution of primates.

Evidence for evolutionary human origin

Option 2

1 . What were the extinct arboreal humans called?different monkeys that are the ancestors of moderngreat apes and humans?
1) hominids 3) driopithecus
2) tarsiers 4) pongids

2 . Which pre-existing group of tarsierhidden in the evolutionary trunk of the monkeys of the OldSveta?

1) lemurs 3) ramapithecus
2) necrolemurs 4) baboons

3 . Which scientist for the first time in his work proved the relationshipman with great apes?
1) K. Linnaeus2) T. Huxley
3) J.B. Lamarck4) Ch. Darwin

4 . What property of the species Homo sapiens is notsocial?

1) big brain box

2) the creation and use of tools

3) consciousness and speech

4) public lifestyle

5 . How is the word "Australia" translated from Latin?lopithecus"?

1) Australian monkey|

2) the oldest monkey

3) great ape

4) southern monkey

6 . Fossils of what ancient manwere found near Beijing?

1) Pithecanthropus

2) paleoanthrope

3) synanthropus

4) Australopithecus

7. What are the names of the first representatives of biologicalkind of Homo sapiens?

1) australopithecines

2) Cro-Magnons

3) Neanderthals

4) paleoanthropes

8. At what stage did Sinanthropus and Pithecanthus appear?rops?

1) at the stage of archanthropes

2) at the stage of paleoanthropes

3) at the stage of neoanthropes

4) at the stage of protoanthropes

9. Which of the following structural features of the human skull is an adaptation to speech?

1) the presence of a protruding chin

2) vertical forehead

3) fusion of the bones of the skull

4) enlarged in comparison with the facial brain part of the skull

10. In humans, unlike the orangutan

1) more facial part of the skull

2) more brain volume

3) the upper limbs are longer than the lower ones

4) the chest is formed by ribs

11. What factor of human evolution is considered to be social?

1) labor activity

2) hereditary variability

3) struggle for existence

4) natural selection

12. Which feature of the class Mammals is characteristic of humans?

1) diaphragm

2) pulmonary respiration

3) brain and spinal cord

4) closed circulatory system

13. Which of the representatives of the genus Man belongs to the presented images of rock paintings?

1) Pithecanthropus

2) Neanderthal

3) Cro-Magnon

4) Australopithecus

14. To the group of ancient people, scientists include

1) Cro-Magnons

2) australopithecines

3) Neanderthals

4) synanthropes

15. Determine the correct sequence of the main stages of human evolution.

1) ancient people⇒ forerunners of humans⇒ Neanderthals⇒ cro-magnons

2) the predecessors of people⇒ ancient people⇒ Neanderthals ⇒ Cro-Magnons

3) Cro-Magnons ⇒ Neanderthals ⇒ predecessors of people ⇒ ancient people

4) Neanderthals⇒ ancient people⇒ forerunners of humans⇒ cro-magnons

16. What human trait is a trait of chordate type animals?

1) lungs, consisting of alveoli

2) the nervous system of the nodal type

3) hairline

4) gill slits in the wall of the pharynx of the embryo

17. What contributed to the emergence of upright posture in humans?

1) settling new territories

2) faster ground movement

3) closer communication between people

4 ) liberation of the hand and development of labor activity

18. Consider the figure, which shows the fossil ancestors of the genus Man in the chronological order of their appearance on Earth. Under what number is a Cro-Magnon on it, if under the number 1 is an Australopithecus?

1)5

2)4

3)3

4)2

19. How are humans classified as Mammals? Choose three correct answers from six and write down the numbers under which they are indicated.

1) tubular type nervous system

2) gill slits on the pharynx of the embryo

3) four-chambered heart

4) auricles

5) the skeleton of the upper and lower limbs

6) furrows and gyrus in the cerebral cortex

20. Establish a correspondence between the example and the factor of anthropogenesis for which it is characteristic.

second signaling system

B)

manifestation of mutations

AT)

struggle for existence

G)

transfer of accumulated experience

D)

traditions and rituals

E)

insulation

biological

2)

social

21 .Set the chronological sequence of taxa,used in the systematics of man, starting with the smallest

1) vertebrates

2) a reasonable person

3) chordates

4) man

5) mammals

6) eukaryotes

But, acquiring an increasingly civilized appearance, a person tried not to perceive a chimpanzee or a gorilla as his likeness, because he quickly realized himself as the crown of creation of the almighty creator.

When theories of evolution appeared, suggesting the initial link in the origin of Homo sapiens in primates, they were met with incredulity, and more often with hostility. Ancient monkeys, located at the very beginning of the pedigree of some English lord, were perceived at best with humor. Today, science has identified the direct ancestors of our biological species, who lived more than 25 million years ago.

common ancestor

From the point of view of modern anthropology, the science of man, of his origin, it is considered incorrect to say that a person descended from a monkey. Man as a species evolved from the first people (they are usually called hominids), which were a radically different biological species than monkeys. The first great human - Australopithecus - appeared 6.5 million years ago, and the ancient monkeys, which became our common ancestor with modern anthropoid primates, about 30 million years ago.

Methods for studying bone remains - the only evidence of ancient animals that have survived to our time - are constantly being improved. The oldest ape can often be classified by a jaw fragment or a single tooth. This leads to the fact that more and more new links appear in the scheme, complementing the overall picture. In the 21st century alone, more than a dozen such objects were found in various regions of the planet.

Classification

The data of modern anthropology are constantly updated, which makes adjustments to the classification of biological species to which a person belongs. This applies to more detailed divisions, while the overall system remains unshakable. According to the latest views, man belongs to the class Mammals, order Primates, suborder Real monkeys, family Hominid, genus Man, species and subspecies Homo sapiens.

The classification of the closest "relatives" of a person is the subject of constant debate. One option might look like this:

• Squad Primates:
  • Half-monkeys.
  • real monkeys:
    • Dolgopyatovye.
    • Broad-nosed.
    • Narrow-nosed:
      • Gibbon.
      • Hominids:
        • Pongins:
          • Orangutan.
          • Bornean orangutan.
          • Sumatran orangutan.
      • Hominins:
        • Gorillas:
          • Western gorilla.
          • Eastern gorilla.
        • Chimpanzee:
          • common chimpanzee.
        • People:
          • A reasonable person.

Origin of monkeys

Determining the exact time and place of origin of monkeys, like many other biological species, occurs like a gradually emerging image on a Polaroid photograph. The finds in different regions of the planet supplement the overall picture in detail, which is becoming clearer. At the same time, it is recognized that evolution is not a straight line - it is rather like a bush, where many branches become dead ends. Therefore, it is still a long way to build at least a segment of a clear path from primitive primate-like mammals to Homo sapiens, but there are already several reference points.

Purgatorius - a small, no larger than a mouse, animal lived in trees, eating insects, in the Upper Cretaceous and (100-60 million years ago). Scientists put him at the beginning of the chain of evolution of primates. It revealed only the beginnings of signs (anatomical, behavioral, etc.) characteristic of monkeys: a relatively large brain, five fingers on the limbs, lower fecundity with no seasonality of reproduction, omnivorousness, etc.

Beginning of hominids

Ancient apes, the ancestors of anthropoids, left traces starting from the late Oligocene (33-23 million years ago). They still retain the anatomical features of narrow-nosed monkeys, put by anthropologists at a lower level: a short auditory meatus located outside, in some species - the presence of a tail, the lack of specialization of the limbs in proportion and some structural features of the skeleton in the area of ​​the wrists and feet.

Among these fossil animals, proconsulids are considered one of the most ancient. The peculiarities of the structure of the teeth, the proportions and dimensions of the cranium with an enlarged brain region relative to its other parts allow paleoanthropologists to classify proconsulids as anthropoid. This species of fossil monkeys includes proconsuls, kalepithecus, heliopithecus, nyanzapithecus, etc. These names were most often formed from the name of geographical objects near which fossil fragments were found.

Rukvapitek

Most of the finds of the most ancient bones of paleoanthropologists are made on the African continent. In February 2013, paleoprimatologists from the United States, Australia and Tanzania published a report on the results of excavations in the Rukwa River Valley in southwestern Tanzania. They discovered a fragment of the lower jaw with four teeth - the remains of a creature that lived there 25.2 million years ago - this was the age of the rock in which this find was discovered.

According to the details of the structure of the jaw and teeth, it was established that their owner belonged to the most primitive anthropoid apes from the proconsulid family. Rukvapitek - this is the name of this hominin ancestor, the oldest fossil great ape, because it is 3 million years older than any other paleoprimates discovered before 2013. There are other opinions, but they are connected with the fact that many scientists consider the proconsulids to be too primitive beings to define them as true humanoids. But this is a question of classification, one of the most controversial in science.

Dryopithecus

In the geological deposits of the Miocene era (12-8 million years ago) in East Africa, Europe and China, the remains of animals were found, to which paleoanthropologists assigned the role of an evolutionary branch from proconsulids to true hominids. Driopithecus (Greek "drios" - tree) - the so-called ancient monkeys, which became a common ancestor for chimpanzees, gorillas and humans. The places of the finds and their dating make it possible to understand that these monkeys, outwardly very similar to modern chimpanzees, formed into a vast population, first in Africa, and then spread across Europe and the Eurasian continent.

About 60 cm tall, these animals tried to move on their lower limbs, but mostly lived in trees and had longer “arms”. The ancient dryopithecus monkeys ate berries and fruits, which follows from the structure of their molars, which did not have a very thick layer of enamel. This shows a clear relationship of driopithecus with humans, and the presence of well-developed fangs makes them an unequivocal ancestor of other hominids - chimpanzees and gorillas.

Gigantopithecus

In 1936, several unusual monkey teeth, remotely similar to human ones, accidentally fell into the hands of paleontologists. They became the reason for the emergence of a version about their belonging to beings from an unknown evolutionary branch of human ancestors. The main reason for the appearance of such theories was the huge size of the teeth - they were twice the size of the teeth of a gorilla. According to the calculations of experts, it turned out that their owners had a height of more than 3 meters!

After 20 years, a whole jaw with similar teeth was discovered, and the ancient giant monkeys turned from a creepy fantasy into a scientific fact. After a more accurate dating of the finds, it became clear that huge anthropoid primates existed at the same time as the Pithecanthropus (Greek "pithekos" - monkey) - ape-men, that is, about 1 million years ago. The opinion was expressed that they were the direct predecessors of man, involved in the disappearance of the largest of all monkeys that existed on the planet.

herbivorous giants

Analysis of the environment in which fragments of giant bones were found, and the study of the jaws and teeth themselves, made it possible to establish that bamboo and other vegetation served as the main food for Gigantopithecus. But there were cases of discovery in caves, where they found the bones of monster monkeys, horns and hooves, which made it possible to consider them omnivores. Giant stone tools were also found there.

A logical conclusion followed from this: Gigantopithecus - an ancient anthropoid ape up to 4 meters tall and weighing about half a ton - is another unrealized branch of hominization. It has been established that the time of their extinction coincided with the disappearance of other anthropoid giants - African Australopithecus. A possible reason is climatic cataclysms that have become fatal for large hominids.

According to the theories of the so-called cryptozoologists (Greek "cryptos" - secret, hidden), individual Gigantopithecus individuals have survived to our times and exist in areas of the Earth that are difficult for people to reach, giving rise to legends about the "Bigfoot", Yeti, Bigfoot, Almasty and so on.

White spots in the biography of Homo sapiens

Despite the successes of paleoanthropology, in the evolutionary chain, where the first place is occupied by the ancient apes, from which man descended, there are gaps lasting up to a million years. They are expressed in the absence of links that have scientific - genetic, microbiological, anatomical, etc. - confirmation of the relationship with previous and subsequent types of hominids.

There is no doubt that gradually such white spots will disappear, and sensations about the extraterrestrial or divine beginning of our civilization, which are periodically announced on entertainment channels, have nothing to do with real science.

Key questions

What is evolution and poppy proof of its existence?

To us and from whom did man come?

Why did one species of animal have to undergo such a rapid evolution during the last century?

In 1831, Charles Darwin went on a voyage on the ship "Beagle" as a naturalist. As he set out on his journey, he shared the popular belief that every existing species is unique and permanent, and that worldwide catastrophes wiped out previous populations, evidence of which was preserved as fossils, and new species arose in their place.

Returning from a trip almost five years later, Darwin already had a different opinion. He became convinced that organisms evolve slowly, and fossils - the ancestors of existing forms - are partial evidence of this process.

What made Darwin change his idea of ​​the origin of life? During a round-the-world trip on the Beagle, Darwin collected facts that testify to the evolution of species. Of course, these facts were not so numerous compared to the bright and convincing examples that evolutionists have discovered over the past 100 years or more. However, Darwin saw a lot and did a lot on the material he saw, which will be the subject of discussion in this and subsequent chapters.

19.1. Evolution - a change in the inherited phenotypes (inherited manifestations of traits) of individuals in a population

Evolution is a special kind of change that can only occur in a group of organisms. An individual does not evolve.

Evolution happens inside populations, which can be defined as a group of organisms of the same species living in a more or less limited area.

The process of evolution consists in changing the inherited phenotype, i.e., the external manifestation of the hereditary characteristics of the organism, such as color, size, biochemical composition, development rate, behavior, etc.

Evolution in a population can occur even if evolutionary change does not occur in a particular individual. An adult gray moth does not become black, just as a bacterium does not become resistant to a drug, but one of the gray moth's offspring may turn out to be black, etc. At different times, the population consists of different individuals, and therefore it reflects the general changes that have occurred over many generations. If a population is examined twice after a long period of time, and if it turns out that during this period new phenotypes have appeared in the population that can be transmitted to future generations, then we can say that evolution has occurred in the population (Fig. 19-1).

19.2. As a rule, information about previous populations exists only in the form of fossil remains.

Since a noticeable evolutionary change usually occurs after thousands or millions of years, evolution can be traced by comparing modern populations with ancient ones that have survived only partially as fossils. We cannot be sure that the fossils we find are representative of their populations, but our knowledge of the fossilization process suggests that they are. The close correspondence between individual fossils and the populations they represent is amply confirmed when a living "fossil" is discovered - a living member of a supposedly extinct fossil group.

For example, the lobe-finned fish Latimeria belongs to an ancient subfamily of fish, which for a long time we knew only from the presence of fossil remains. Scientists believed that all species of lobe-finned fish became extinct 75 million years ago. But in 1939, in the waters of the Malagasy Republic, a live lobe-finned fish was caught at great depths, followed by others.

From Figure 19-2, it becomes apparent that the phenotype of this fish, reconstructed from fossils, is remarkably similar to that of its modern relatives. Such examples allow scientists to use fossil material with certainty.

For reference

Each element has several varieties, called isotopes. Isotopes differ in that their atoms contain different numbers of neutrons. Since the atomic mass of an element is approximately the sum of protons and neutrons, isotopes of the same element have different atomic masses. To designate isotopes of the same element, their atomic mass (rounded to the nearest whole number) is written to the left of, and slightly above, the sign of the element. For example, 14 C is a radioactive isotope of carbon. Other carbon isotopes are stable (non-radioactive), such as 12 C. Each radioactive isotope of any element has a certain half-life.

19.3. The age of fossils is most often determined by examining the radioactive substances they contain.

radioactive substances break apart and are converted into other substances. For example, radioactive uranium decays into lead and helium (a resistant gas), radioactive potassium turns into argon (a resistant gas) and ordinary calcium, radioactive carbon turns into nitrogen, etc.

Some radioactive transformations occur within a few hours, others within a few years, and some over entire epochs. In 456 billion years, only half of a certain amount of 238 U (an isotope of uranium) will turn into lead and helium. The time it takes for half of a given amount of a substance to decay is called half-life. Every radioactive substance has a certain half-life. If the half-life is known, it can be used to determine the age of rocks and the fossils they contain. For example, when the 1.0 g uranium isotope 238 U decays to 0.5 g in 456 billion years, 0.4 g of lead is formed (the rest of the mass is converted into helium and nuclear energy). In another 456 billion years, only 0.25 g of uranium will remain, but the amount of lead will increase to 0.6 g. To determine the age of the rock, the relative content of uranium and lead in it is measured. The greater the amount of uranium relative to lead, the younger the rock.

The half-life of the uranium isotope 238 U is too long to be used in determining the age of later fossils. The half-life of the uranium isotope 235 U is 713 million years. And the potassium isotope 40 K turns into the argon isotope A, having a half-life of 13 billion years. These half-lives are quite applicable for determining the age of many fossils.

Another useful isotope is the carbon isotope 14 C. It is present together with ordinary carbon in all living organisms as a small but constant fraction of living tissue. Like all radioactive elements, it is constantly decaying. But while the organism lives, the amount of radioactive carbon in it is replenished as it decays. After the death of the organism, the content of 14 C in relation to the total amount of carbon in dead tissues begins to decrease. In fact, in 5570 years it will be half as much. Therefore, comparing the amount of ordinary carbon with the amount of radioactive carbon allows us to determine the age of the latest fossils, as well as teeth, bones, remains of wood and charcoal, dating back 10,000 years.

In general, the "repertoire" of radioactive tests now covers the entire period (of life on Earth. Thus, the age of most fossils can be determined now more accurately than ever before.

19.4. To study human evolution, i.e., the divergence between hominids (humans) and pongids (great apes), it is necessary to consider the differences between them

Since there are people who are unwilling to admit that the process of evolution includes man, we have chosen him as an example of evolution, although many other organisms could serve as a good or even better example, especially those whose remains have been preserved in places where decomposition is under bacterial influence was minimal.

The reconstruction of human evolution should begin with a study of the differences between humans and great apes. Knowing them, we will know what to look for in order to establish common ancestors or "missing links". There are relatively few anatomical differences between apes and humans. The human brain is much larger, and the forehead is higher. The jaws are shorter than those of monkeys, and the face, on which the nose protrudes, is flatter. Human teeth are arranged in the jaws in the form of a gracefully curved arch called the dental arch. In monkeys, the dental arch is whiter rectangular than arched. Some teeth in monkeys are separated by a relatively large distance, and in humans, the teeth are in contact with each other. Besides, the fangs, or eye teeth, are not longer in man than other teeth; in monkeys, they are longer and resemble teeth.

Human - bipedal a vertically walking creature. The method of movement of the monkeys is called brachiation, they throw the body from tree to tree, clinging to the branches with their hands. Since man is a two-legged creature, he differs from the great apes in that he has: 1) a wide bowl-shaped pelvis; 2) large muscular buttocks; 3) a fairly powerful heel; 4) long cogs; 5) arched foot; 6) S-shaped spine; 7) foramen magnum (a large opening at the base of the skull through which the spinal cord passes), facing downwards, and not backwards, as in monkeys (Fig. 19-3). There are other differences, such as the relative lack of hair and priapic bone(bones of the penis) in humans.

Since the bones are easily fossilized, we can hope that we will be able to fully trace the evolutionary differences in the skeleton of man and great apes. However, there are significant differences between humans and great apes that are not subject to fossilization: ^ human puberty lasts longer (17 years for humans, 8-10 years for monkeys); 2) a person can be left-handed and right-handed; 3) people unite in large groups and use complex means of transmitting thoughts, signs and abstract concepts to each other; 4) man is able to produce offspring throughout the year, while monkeys breed at certain periods / However, there is one, "non-skeletal" difference, which is very well "fossilized". People create tools that shape and reflect their complex culture.

There are more similarities between man and great apes, not-I*ate differences. They share many anatomical and biochemical features. For example, neither humans nor great apes are capable of synthesizing vitamin C and do not have tails.

19.5. Possible common ancestors of modern great apes and humans are extinct arboreal apes that lived about 15-30 million years ago

15 million years ago, neither modern apes nor humans existed. Fossils of ape-like primates have been found, which, apparently, are their common ancestors. The age of these fossils is approximately 15-30 million years. However, the remains of these ancient fossils are very scarce. Most often this is only a part of the jaw, sometimes only one tooth, less often - finds approaching the full skeleton. For our discussion, of greatest interest are fossils belonging to the group of driopithecus - tree monkeys (Fig. 19-4), the remains of which were found in Africa, India and Europe. They are the likely ancestors of great apes, such as the gorilla and chimpanzee, and appear to be closely related to human ancestors.

The pelvis of the dryopithecus is adapted for locomotion on four legs, but its size was smaller than that of modern chimpanzees and gorillas. Their legs were not as long as those of a human, and their arms were shorter than those of a chimpanzee or an orangutan. Some dryopithecus have fangs (eye teeth) larger than those of humans, but smaller than those of modern great apes. The roots of the canine teeth in humans are larger than seems necessary. This suggests that our ancestors had larger fangs. There is also a similarity between the molars of humans and driopithecus.

The dentition of dryopithecus is not the same, since they belonged to several different families, genera and species. Most dryopithecus teeth were similar to those of monkeys, but there are also those that have a more rounded dental arch, relatively small fangs, and other similarities with human teeth. Elwyn Simons united humanoid forms under a common name Ramaptihecus punjabicus.

These fossils lived in Africa and India, and possibly in the territory located between them. They lived about 14 million years ago, as determined by dating based on the radioactive conversion of potassium to argon, carried out at the site where one of them was discovered by the late Lewis Leakey (Lewis Leakey).

Leakey and Simone disagreed on the names of certain anthropoid fossils, but they agreed on their origin, namely that 12-14 million years ago, animals that showed signs of developing ape-like features that we observe in modern pongids lived in warmer climes. Old World.

Together with them there was a group of primates, very similar in appearance, whose teeth had a clear resemblance to human teeth. (Simone called them Ramapithecus.) Leakey formally separated these humanoid jaw-bearers from the Dryopithecus group and assigned them to the hominid family.

Extremely important information was obtained from the discovery of the remains of the fossil Ramapithecus, known as the "Calcutta jaw". They show that the maturation period of Ramapithecus, in contrast to Pongida, was very long, as in humans. The lower jaw contains all three molars, but with very different wear. The first is heavily worn, the second is only moderately worn, the third is almost completely worn out. This differential wear of molars is seen in humans and fossil humans (including Australopithecus), but is never seen in great apes. According to Simons, the third molar, or wisdom tooth, is a sign of maturity in all humans and great apes. It appears after the development of the skeleton and puberty of the body is completed. In great apes, which have a short period of maturation, molars appear quickly one after another and therefore they are almost uniform in degree of wear. In humans, the first molar erupts at about the same chronological age as in monkeys, but the second appears somewhat later, and the third much later than in monkeys. Therefore, in a person who has reached maturity, the third molar is completely new, and the first is worn out, which is also characteristic of the fossil Ramapithecus.

If all this is confirmed by further findings, the picture of human evolution will appear as follows:

1) The first great apes evolved from Old World monkeys that gradually lost their tail. Then, in the process of divergence of these great apes, forms were formed that, apparently, are the ancestors of driopithecus and gibbons (gibbons are a separate family of great apes). 2) 15-20 million years ago there was a divergence of driopithecus into a) forms from which a person will later appear ( Ramapithecus), and b) the forms from which modern pongids would originate ( Dryopithecus).

19.6. A closer ancestor of man, apparently, was Australopithecus (Australopithecus)

Approximately 2, and perhaps even 3 or 4 million years ago, hominids not only existed, but their anatomy was very similar to that of humans. Even their head had a number of human features. The teeth were almost the same as those of a human, with the exception of the molars, which were larger in size, and the jaws were somewhat smaller than those of Dryopithecus.

R. A. Dart, who first discovered these hominids, did not immediately mistake the small skull he found for a hominid skull, although he drew attention to the fact that the teeth and jaws had many features characteristic of hominids (Fig. 19- 5b, c). So he called his find Australopithecus africanm.

In 1936, ten years after Dart's discovery, Robert B. Broom (Robert B. Broom) discovered the pelvic bones of Australopithecus (Fig. 19-5, A). Except for minor details, their shape clearly resembled the familiar shape of human bones, proving that Australopithecus walked upright.

This was not a complete surprise, since the large foramen magnum in the fossil found by Dart was pointing down, which also indicated the vertical position of the body. In addition, many other anatomical details of the skeleton indicated that Australopithecus was more of a mini-brain human than anything else.

In the late 1950s, Lewis Leakey's wife, Dr. Mary Leakey, unearthed the most amazing of all finds: Australopithecus skeletal remains, along with the earliest known type of stone tools.

Based on the radioactive decay of potassium, it was found that the age of the remains is 1.75 million years, i.e. this proved that A. africanm created tools.

19.7. Gradually, A. africanus evolved into a form called A. habilis, from which, in turn, Homo erectus evolved about a million years ago.

Although, thanks to the Leakeys, most of the finds tracing the process of transformation of Australopithecus africanus into Homo erectus were found in Tanzania (which was partly facilitated by the Tanzanian climate), Homo erectus was first found by the Danish physician Eugene Dubois in Java in 1891.

Dubois suggested that Java is the place to look for the "missing link". Going there, he found what he was looking for! The species he discovered is now found in most of the tropical and temperate zones of the Old World. However, his luck is still amazing. For 40 years, other expeditions tried unsuccessfully to replicate his discovery.

At first, Dubois' find was called Pithecanthropus erectus(upright ape-man), but now this species has received the name Homo erectus(upright person).

Anatomical changes in Homo erectus were observed mainly in the skull.

The size of his brain approached the size of the brain of a modern person. And some representatives of H. erectus had the same brain as some modern H. sapiens with a small brain volume.

Speaking about the volume of the human brain, it should be noted that the most famous H. sapiens with a small skull size was the French writer Anatole France, whose skull volume was only 1017 cm 3 with an average volume of 1350 cm 3. Thus, this does not mean at all that N. erectus was an imbecile creature. The tools he made testify to his extraordinary ability and technical skill.

Apparently, H. erectus had other similarities with the behavior of modern man: several carefully opened skulls of H. erectus were found as if their contents had been eaten during a cannibal feast or ritual.

19.8. The increase in the volume of the human brain over the past 2 million years is one of the fastest evolutionary changes

Now there is a whole series of found fossil skulls that allow you to carefully trace the path from A. africanus with a mini-brain to H. sapiens. Although the growth of the brain has occurred in relatively small steps, it is one of the most rapid evolutionary changes in the history of life on Earth. In less than 2 million years, the average brain volume of hominids has more than doubled. This is an exceptional speed compared to the usual pace of evolution. For example, the evolution of a horse from its dog-sized ancestors to its modern form took place over 60 million years.

The volume of the human brain is no longer increasing, and apparently the pH has remained that way for nearly 250,000 years. In fact, H. sapiens neanderthalensis(Neanderthal man, a race of our species that "thrived" during the last ice age) brain volume was on average 100 cm 3 larger than that of a modern person. It is likely that the brain is no longer enlarged, since the already large size of the newborn's head barely allows it to pass through the mother's pelvis, which must open slightly during childbirth to ensure the birth of the child. But there may have been other, even more important reasons.

19.9. The evolution of Homo erectus into Homo sapiens ended about 300,000 years ago

Paleontologists believe that N. erectus evolved into Homo sapiens about 300,000 years ago, but they acknowledge that this figure is somewhat arbitrary. The evolution of human anatomy, behavior and physiology, that is, the human phenotype, is a gradual process. It continues to this day.

19.10. There is evidence of the evolution of a species of butterfly over the past 100 years or more

The first documented observation of evolution involved butterflies, which developed black coloration as the forest environment in which they lived increased in completeness.

As early as Darwin's youth, almost all British Biston betularia butterflies were spotted pale gray and white. A black form of Biston betularia also existed but was rare. We know this because it was in high demand among collectors. And now the forests of Birmingham in England are full of them, and they are as common as they once were. Evolution has taken place in our time.

Modern biologists have noticed that the black form is common in areas located east of large industrial centers such as Birmingham, and, knowing that in England the winds usually blow from west to east, they suggested that smoke and soot from factories and factories somehow influenced the formation of black uniforms. British biologist

H. B. D. Kettlewell observed that in forests where black butterflies were found, the trees were black and sooty, and forests where there were still many gray and white spotted butterflies, the old "typical form ", relatively clean. The trunks in these forests were covered with variegated gray-white lichen. He established that the black color in butterflies is associated with natural pigmentation and is inherited, like the typical spotted form.

Kettlewell suggested that since birds are the most dangerous enemies of butterflies, the more conspicuous a butterfly was sitting on a tree trunk, the more likely it could be seen and eaten. Therefore, the spotted butterfly was relatively safe on a trunk covered with lichen, and the black one on a trunk covered with soot (Fig. 19-6). To test his hypothesis, Kettlewell bred butterflies of both forms and released them into clean and sooty forests. Before releasing them, he painted a dot under the wing of each butterfly. Kettlewell released 799 butterflies into lichen-covered forests and after 11 days captured 73 butterflies with his mark.

Spotted butterflies were more likely to survive among lichen-covered trees. Over an 11-day period, each spotted butterfly was about 2.9 times more likely to survive than the black butterfly.

In smoky forests, the black form of butterflies had an advantage. Here the experiment was carried out 2 times. In 1953, 27.5% of black butterflies and only 13% of spotted butterflies were caught in 11 days. During this period, the survival rate of black butterflies was 2.1 times higher than that of spotted butterflies. In 1955, the survival rate of black butterflies was again 2.1 times greater.

Kettlewell used filming to record the actions of birds given the opportunity to catch one of two species of butterflies perched in a tree in front of them. In Birmingham, birds noticed black butterflies much less frequently. For example, redstarts ate 43 spotted butterflies and only 15 black butterflies in two days. In pure forests it was the other way around. The gray flycatcher ate 81 black butterflies and 9 spotted ones. Filming showed that it was not easy for birds to see spotted butterflies against a spotted background of lichens and black butterflies against a dark background of soot. Not surprisingly, in a sooty environment, about 100 species of butterflies began to acquire a dark color.

There are other cases of observed evolution known to science, many of which are due to our radical intervention in nature. One of them is the acquisition of resistance to DDT by mosquitoes. Another case is the acquisition of resistance to antibiotics by infectious bacteria. These examples, as well as fossil evidence, support the fact of evolution. Thus, we have come to the next question: what causes biological evolution?

Great apes, or ( Hominoidae) is a superfamily of primates, which includes 24 species. Although people are Hominoidea, the term "ape" does not apply to humans and describes non-human primates.

Classification

Great apes are classified in the following taxonomic hierarchy:

• Domain: ;
• Kingdom: ;
• Type of: ;
• Class: ;
• Squad: ;
• Superfamily: Hominoids.

The term great ape refers to a group of primates that includes the families: hominids (chimpanzees, gorillas, orangutans) and gibbons. scientific name Hominoidea refers to apes (chimpanzees, gorillas, orangutans, gibbons) as well as humans (i.e. ignoring the fact that humans prefer not to call themselves apes).

The gibbon family is the most diverse, it has 16 species. Another family - hominids - is less diverse and includes: chimpanzees (2 species), gorillas (2 species), orangutans (3 species) and humans (1 species).

Evolution

The record is incomplete, but scientists believe that ancient hominoids diverged from marmosets between 29 and 34 million years ago. The first modern hominoids appeared about 25 million years ago. Gibbons were the first group to split off from other groups, about 18 million years ago, followed by a lineage of orangutans (about 14 million years ago), and gorillas (about 7 million years ago).

The most recent split occurred between humans and chimpanzees about 5 million years ago. The closest living relatives of hominoids are the Old World monkeys, or marmosets.

Environment and habitat

Hominoids live throughout the West and Central, as well as in the Southeast. Orangutans are found only in Asia, chimpanzees inhabit West and Central Africa, gorillas are common in Central Africa, and gibbons live in Southeast Asia.

Description

Most hominoids, with the exception of humans and gorillas, are skilled as well as flexible climbers. Gibbons are the most agile arboreal primates of all hominids. They can jump up branches, moving quickly and efficiently through trees.

Compared to other primates, hominoids have a lower center of gravity, a shortened spine relative to their body length, a broad pelvis, and broad chest. Their overall build gives them a more upright posture than other primates. Their shoulder blades are on their backs, allowing for a wide range of motion. Hominoids also do not have a tail. Together, these characteristics give hominoids a better balance than their closest living relatives, the Old World monkeys. Hominoids are therefore more stable when standing on two legs or swinging their limbs and hanging from tree branches.

Hominoids are very intelligent and able to solve problems. Chimpanzees and orangutans make and use simple tools. Scientists studying orangutans in captivity have noted the ability of these primates to use sign language, solve puzzles and recognize symbols.

Food

The diet of hominoids includes leaves, seeds, nuts, fruits, and a limited number of animals. Most species but fruits are the preferred food. Chimpanzees and orangutans primarily eat fruits. When fruit is scarce at certain times of the year or in certain regions, gorillas feed on shoots and leaves, often bamboo. Gorillas are well adapted to chewing and digesting such a low-nutrient food, but these primates still prefer fruit when available. Hominoid teeth are similar to those of Old World monkeys, although they are especially large in gorillas.

reproduction

Gestation in hominoids lasts from 7 to 9 months and leads to the birth of one offspring or, more rarely, two. Cubs are born helpless and require care for a long time. Compared to most other mammals, hominoids have a surprisingly long period of breastfeeding. In most species, full maturity occurs at the age of 8-13 years. As a result, females typically give birth only once every few years.

Behavior

Like most primates, hominoids form social groups whose structure varies by species. Gibbons form monogamous pairs. Orangutans are an exception to the social norm of primates, they lead a solitary life.

Chimpanzees form groups that can number from 40 to 100 individuals. Large groups of chimpanzees break up into smaller groups when fruit becomes less available. If small groups of dominant male chimpanzees leave to feed, the females often copulate with other males in their group.

Gorillas live in groups of 5 to 10 or more individuals, however they stay together regardless of the presence of fruit. When fruit fruits are hard to come by, they resort to eating leaves and shoots. Since the gorillas stay together, the male is able to monopolize the females in his group. This fact is associated with more in gorillas than in chimpanzees. In both chimpanzees and gorillas, groups include at least one dominant male, with females leaving the group at adulthood.

Threats

Many species of hominoids are endangered due to destruction, poaching and hunting for bushmeat and skins. Both species of chimpanzee are endangered. Gorillas are on the verge of extinction. Eleven out of sixteen gibbon species are becoming extinct.