The Origin of Humankind

by Richard Leakey

  When change did come, however, it was dazzling—so dazzling that we should be aware that we might be blind to the reality behind it. About 35,000 years ago in Europe, people began making tools of the finest form, fashioned from delicately struck stone blades. For the first time, bone and antler were used as raw material for toolmaking. Tool kits now comprised more than one hundred items, and included implements for fashioning rough clothing and for engraving and sculpting. For the first time, tools became works of art: antler spear throwers, for example, were adorned with lifelike animal carvings. Beads and pendants appear in the fossil record, announcing the new practice of body decoration. And—most evocative of all—paintings on the walls of deep caves speak of a mental world we readily recognize as our own. Unlike previous eras, when stasis dominated, innovation is now the essence of culture, with change being measured in millennia rather than hundreds of millennia. Known as the Upper Paleolithic Revolution, this collective archeological signal is unmistakable evidence of the modern human mind at work.

  Now, I said that the archeological signal of the Upper Paleolithic Revolution might be blinding us to reality. By this I mean that for historical reasons the known archeological record in Western Europe is far richer than in Africa. For every archeological site of this era in Africa, there are about two hundred such sites in Western Europe. The disparity reflects a difference in the intensity of scientific exploration in the two continents, not the reality of human prehistory. For a long time, the Upper Paleolithic Revolution was taken as an indication that the final emergence of modern humans occurred in Western Europe. After all, the archeological signal and the fossil record coincided there precisely: both indicate a dramatic event about 35,000 years ago: modern humans appeared in Western Europe 35,000 years ago and their modern behavior is immediately part of the archeological record. Or so it was assumed.

  Recently, this view has changed. Western Europe is now recognized as something of a backwater, and we can discern a transformation sweeping across Europe, from east to west. Beginning about 50,000 years ago, in Eastern Europe, the existing Neanderthal populations disappeared and were replaced by modern humans, the final replacement taking place in the far west by about 33,000 years ago. The coincidental appearance of modern humans and modern human behavior in Western Europe reflects the influx of a new kind of population, modern Homo sapiens. The Upper Paleolithic Revolution in Europe was a demographic signal and not an evolutionary signal.

  If modern humans were migrating into Western Europe beginning 50,000 years ago, where did they come from? On the basis of the fossil evidence, we would say Africa, in all probability—or perhaps the Middle East. Despite the paucity of the archeological record, it does support an African origin of modern human behavior. Technologies based on narrow blades begin to appear on that continent around 100,000 years ago. This, remember, would coincide with the first known appearance of modern human anatomy, and could be taken as a third example of the link between biology and behavior.

  The link here may, however, be an illusion, the result of happenstance. I say this because in the Middle East, where both the fossil and archeological records are good, we see something that is clear and yet paradoxical. The application of new dating techniques shows that Neanderthals and modern humans essentially coexisted in the region for as long as 60,000 years. (In 1989, the Tabun Neanderthal was shown to be at least 100,000 years old, making it a contemporary of the modern humans from Qafzeh and Skhul.) Throughout that time, the only form of tool technology we see is that associated with Neanderthals. The name given to their technology is Mousterian, after the cave of Le Moustier, in France, where it was first discovered. The fact that the anatomically modern human populations in the Middle East appear to have manufactured Mousterianlike technology rather than the innovation-rich tool assemblages so characteristic of the Upper Paleolithic means that they were modern in form only, and not in their behavior. The link between anatomy and behavior therefore seems to break. The archeological signal of the earliest modern human behavior is weak and sporadic, and may be the victim of the poorly known record. Although blade-based technology is seen first in Africa, it isn’t possible to point confidently to the African continent and say, “This is where modern human behavior began,” and then trace its expansion into Eurasia.

  The third line of evidence bearing on the origin of modern humans, that of molecular genetics, is the least equivocal. It is also the most controversial. During the 1980s, a new model of modern human origins emerged. Known as the mitochondrial Eve hypothesis, it essentially supported the “Out of Africa” model, cogently so. Most proponents of the “Out of Africa” hypothesis are prepared to entertain the possibility that as modern humans expanded from Africa to the rest of the Old World they interbred to some degree with established premodern populations. This would allow for some threads of genetic continuity from ancient populations through to modern ones. The mitochondrial Eve model, however, refutes this. According to this model, as modern populations migrated out of Africa and grew in numbers, they completely replaced existing premodern populations. Interbreeding between the immigrant and existing populations, if it occurred at all, did so to an infinitesimal degree.

  The mitochondrial Eve model flowed from the work of two laboratories—that of Douglas Wallace and his colleagues at Emory University, and of Allan Wilson and his colleagues at the University of California, Berkeley. They scrutinized the genetic material, or DNA, that occurs in tiny organelles within the cell called mitochondria. When an egg from a mother and sperm from a father fuse, the only mitochondria that become part of the cells of the newly formed embryo are from the egg. Therefore, mitochondrial DNA is inherited solely through the maternal line.

  For several technical reasons, mitochondrial DNA is particularly suited to peering back through the generations in order to glimpse the course of evolution. And since the DNA is inherited through the maternal line, it eventually leads to a single ancestral female. According to the analyses, modern humans can trace their genetic ancestry to a female who lived in Africa perhaps 150,000 years ago. (It should be borne in mind, however, that this one female was part of a population of as many as 10,000 individuals; she was not a lone Eve with her Adam.)

  Not only did the analyses indicate an African origin for modern humans, but they also revealed no evidence of interbreeding with premodern populations. All the samples of mitochondrial DNA analyzed so far from living human populations are remarkably similar to one another, indicating a common, recent origin. If genetic mixing between modern and archaic sapiens had occurred, some people would have mitochondrial DNA very different from the average, indicating its ancient origin. So far, with more than 4000 people from around the world having been tested, no such ancient mitochondrial DNA has been found. All the mitochondrial DNA types from modern populations that have been examined appear to be of recent origin. The implication is that modern newcomers completely replaced ancient populations—the process having begun in Africa 150,000 years ago and then having spread through Eurasia over the next 100,000 years.

  When Allan Wilson and his team first published their results, in a January 1987 issue of Nature, the conclusions were stated boldly, provoking consternation among anthropologists and wide interest among the public. Wilson and his colleagues wrote that their data indicated that “the transformation of archaic to modern forms of Homo sapiens occurred first in Africa, about 100,000 to 140,000 years ago, and ... all present-day humans are descendants of that population.” (Later analyses produced slightly earlier dates.) Douglas Wallace and his colleagues generally supported the Berkeley group’s conclusions.

  Milford Wolpoff stuck to his multiregional model of evolution and denounced the data and analyses as unsound, but Wilson and his colleagues continued to produce more data and eventually stated that the conclusions were statistically unassailable. Recently, however, some statistical problems in the analysis were discovered, and the conclusions were recognized as being less concrete than had been asserte
d. Nevertheless, many molecular biologists still believe that the mitochondrial DNA data sufficiently support the “Out of Africa” hypothesis. And it should be noted that more conventional genetic evidence, based on DNA in the nucleus, is beginning to reveal the same kind of pattern shown by the mitochondrial DNA data.

  Those who promote the notion of complete or even partial replacement of premodern by modern populations have an uncomfortable issue to face: How did that replacement occur? According to Milford Wolpoff, such a scenario requires that we accepted violent genocide. We are familiar with killing of this nature in the decimation of Native American and Australian aborigine populations in the nineteenth century. And it may have been true in ancient times, too, although as yet there is not a shred of evidence for this.

  Given the absence of evidence, we are forced to look for possible alternatives to the proposed one of violence. If none exists, then that hypothesis becomes stronger, though unproved. Ezra Zubrow, an anthropologist at the State University of New York, Buffalo, has pursued such an alternative model. He has developed computer models of interacting populations, in which one has a slight competitive edge over the other. By running such simulations he is able to determine what kind of advantage might be required by the superior population in order to replace the second very rapidly. The answer is counterintuitive: a 2 percent advantage can lead to the elimination of the second population within a millennium.

  We can readily understand how one population might destroy another through military superiority. But it is much less easy for us to understand how a slight advantage in, for instance, exploiting resources such as food can play itself out over a relatively short period of time, yielding cataclysmic consequences. If modern humans had a slight advantage over Neanderthals, how are we to explain the apparent coexistence of these two populations for as much as 60,000 years in the Middle East? One explanation is that although modern humans had evolved in anatomical terms, modern human behavior followed later. A second, favored by many, is that the coexistence is more apparent than real. It is possible that the different populations occupied the region by turns, following climatic shifts. In colder times, modern humans moved south and the Neanderthals occupied the Middle East; in warmer times the reverse occurred. Because the time resolution of cave deposits is poor, this kind of “sharing” of a locality can look like coexistence.

  It’s worth noting, however, that where we do know that Neanderthals and modern humans coexisted—in Western Europe, 35,000 years ago—they did so for a millennium or two at most, in accord with Zubrow’s model. Zubrow’s work does not demonstrate unequivocally that demographic competition was the means by which modern humans replaced premodern populations when they encountered them. But it does demonstrate that violence is not the sole candidate as the mechanism for replacement.

  Where does all this leave us? The important issue of the origin of modern humans remains unresolved, despite the welter of information that has been brought to bear. My sense of it, however, is that the multiregional-evolution hypothesis is unlikely to be correct. I suspect that modern Homo sapiens arose as a discrete evolutionary event, somewhere in Africa; but I suspect, too, that when descendants of these first modern humans expanded into Eurasia, they intermixed with the populations there. Why the genetic evidence, as currently interpreted, doesn’t reflect this, I don’t know. Perhaps the current reading of the evidence is incorrect. Or perhaps the mitochondrial Eve hypothesis will turn out to be right, after all. This uncertainty is more likely to be resolved when the clamor of debate ebbs and new evidence is found in support of one or another of the competing hypotheses.

  CHAPTER 6

  THE LANGUAGE OF ART

  There is no question that some of the most potent relics of human prehistory are the depictions of animals and humans—carved, painted, or sculpted—produced within the past 30,000 years. By this time, modern humans had evolved and had occupied much of the Old World, but probably not yet the New World. Wherever people lived—in Africa, in Asia, in Europe, and in Australia—they produced images of their world. The urge to produce depictions was apparently irresistible, and the images themselves are irresistibly evocative. They are also mysterious.

  One of my most memorable experiences as an anthropologist was visiting some of the decorated caves in southwest France in 1980. I was making a series of films for BBC television and so had the opportunity to see what few have been able to see, including the famous cave of Lascaux, near the town of Les Eyzies, in the Dordogne. The most extensively decorated of all caves from Ice Age Europe, Lascaux has been closed to the public since 1963, to protect the integrity of the paintings; currently there is a tight restriction of five visitors a day. Fortunately, a brilliantly rendered duplicate of the cave’s decorated walls has recently been completed, so that the images may still be viewed. My visit to the real Lascaux in 1980 recalled for me a time, three and a half decades ago, when I visited the cave with my parents and Henri Breuil, France’s most famous prehistorian. The images of bulls, horses, and deer were as transfixing on this occasion as they were when I was a youth, as they seem to move before one’s eyes.

  As spectacular as Lascaux is, the cave of the Tuc d’Audoubert, in the Ariège region of France, is unique and arresting. The cave is one of three decorated caves on land owned by Count Robert Bégouën. A narrow, winding passageway leads from bright sunlight several kilometers into the deepest gloom. The count’s flashlight brings the walls to light with dancing shadows, and the clay floor glows orange. Eventually one reaches a small rotunda at the end of the passageway, and the count shines his light with appropriate drama on a spot at the center of the chamber, the ceiling sloping low to the floor beyond. There, one sees the figures of two bison, superbly sculpted from clay, resting against rocks.

  I had seen pictures of these famous figures, of course, but nothing prepared me for reality. Measuring about one-sixth normal size, they are perfect in form, full of movement in their motionlessness; they encapsulate life. The skill of the artists who sculpted these figures 15,000 years ago is breathtaking, especially when one remembers the conditions under which they must have worked. Using simple lamps charged with animal fat, they carried clay from a neighboring chamber and created the animals’ form with their fingers and some kind of flat implement; eyes, nostrils, mouth, and mane were created with a sharp stick or bone. After they had finished, they carefully cleared away most of the debris of their work, leaving only a few sausage-shaped pieces of clay. Once interpreted as phalluses or horns, these are now thought to have been samplers, on which the sculptors tested the plasticity of the clay.

  The reasons for creating the bison and the circumstances under which bison were crafted are lost in time. A third figure is crudely engraved in the floor of the cave near the other two, and there is another statuette, small and again in clay. Most intriguing, however, are heel prints, probably those of children, around the figures. Were the children playing while the artists worked? If so, why do we not see footprints of the artists? Were the heel prints made during a ritual, encapsulating some part of Upper Paleolithic mythology in which the bison figures were the central part? We do not know, perhaps even cannot know. As the South African archeologist David Lewis-Williams says of prehistoric art, “Meaning is always culturally bound.”

  Lewis-Williams, who works at the University of the Witwatersrand, has been studying the art of the !Kung San people of the Kalahari, with an eye toward illuminating the meaning of prehistoric art, including that of Ice Age Europe. He recognizes that artistic expression may form an enigmatic thread in the intricate weave of the cultural fabric of a society. Mythology, music, and dance are also part of that fabric: each thread contributes meaning to the whole, but by themselves they are necessarily incomplete.

  Even if we were to witness the slice of Upper Paleolithic life in which the cave paintings played their role, would we understand the meaning of the whole? I doubt it. We have only to think of the stories related in modern religions to appreciate
the importance of cryptic symbols that may be meaningless outside the culture to which they belong. Think of the meaningfulness to a Christian of an image of a man holding a staff, with a lamb at his feet. And think of the absence of any such meaning to someone who has not heard the Christian story.

  Mine is not a message of despair but of caution. The ancient images we have today are fragments of an ancient story, and although the urge to know what they mean is great, it is wise to accept the probable limits of our understanding. Moreover, there has been a strong, and probably inevitable, Western bias in the perception of prehistoricart. One consequence has been a lack of attention to prehistoric art of equal and sometimes greater antiquity in eastern and southern Africa. Another has been to view the art in the Western way: as though it consisted of pictures hung on a museum wall, as objects simply to view. Indeed, the great French prehistorian Andre Leroi-Gourhan once described the images of the Ice Age as “the origins of Western art.” This is clearly not the case, because at the end of the Ice Age, 10,000 years ago, representational painting and engraving all but disappeared, to be replaced by schematic images and geometric patterns. Many of the techniques that had been applied in Lascaux, such as perspective and a sense of movement, had to be reinvented in Western art with the Renaissance.

  Before we examine some of the attempts to gain a glimpse of Upper Paleolithic life through the medium of ancient images, we should sketch an overall view of Ice Age art. The period in question began 35,000 years ago, and ended some 10,000 years ago, with the end of the Ice Age itself. This period, remember, witnessed the first appearance in Western Europe of sophisticated technology, which evolved rapidly, as if following fashion. The sequence of changes is marked by names given to each new variation of Upper Paleolithic technology, and we can look at the changes in Ice Age art using the same framework.