The Dawn of Human Culture (3 page)
Fish have always been common in the offshore waters near Klasies River Mouth, and roosting cormorants, which sheltered in the caves when people were absent, sometimes carried in tiny fish.
However, in layers where artifacts and fireplaces indicate intense human occupation, fish bones are all but absent. Fish bones are likewise rare or missing at other comparably ancient sites on the South 01 Twilight.r.qxd 1/29/02 5:03 PM Page 20
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African coast, even though the sites were often only a stone’s throw from the sea. At much more recent archeological sites like Nelson Bay Cave, fish bones often dominate the food debris, and the difference probably reflects a difference in technology. Only the more recent sites contain probable fishing gear like grooved stones for weighting nets or lines and carefully shaped toothpick-size bone splinters that could have been baited and tied to lines like hooks. In short, only the more recent people undeniably possessed the technology for fishing.
The ancient Klasies people also largely ignored birds, except for the flightless jackass penguins that they could have caught or scavenged on the beach. Gulls, cormorants, and other airborne birds were surely common nearby, but their bones are scarce at human sites until much more recent times. When they finally do appear in large numbers, they are accompanied by bone rods that were probably parts of arrow shafts and by small stone bits (microliths) like those that historic people used to tip arrows. Historic hunters have often demonstrated the utility of the bow and arrow for fowling. The bottom line is that the archeological and faunal evidence together show that South African hunter-gatherers who lived before 50,000 years ago were much less efficient hunter-gatherers than their successors. Archeology demonstrates that more efficient, fully modern hunting-gathering appeared only after 50,000 years ago, among the kinds of people who made the ostrich eggshell beads at Enkapune Ya Muto.
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time, illustrate a critical conundrum for understanding how, when, and where modern humans evolved. Human fossils from Klasies River Mouth and other African sites and from sites in Israel immediately adjacent to Africa show that people who were anatomically like us had appeared in Africa by 100,000 years ago. Despite their modern appearance, however, these people left artifacts and animal remains which show that they were not fully modern in behavior. It is only after 50,000
years ago that behavioral evolution caught up and it is only afterwards that people were both anatomically and behaviorally modern.
Before 50,000 years ago, human anatomy and human behavior appear to have evolved relatively slowly, more or less in concert. After 50,000 years ago, anatomical evolution all but ceased, while behavioral evolution accelerated dramatically. Now, for the first time, humans possessed the full-blown capacity for culture, based on an almost infinite ability to innovate. They had evolved a unique capacity to adapt to environment not through their anatomy or physiology but through culture. Cultural evolution began to follow its own trajectory, and it took the fast track. Even as our bodies have changed little in the past 50,000 years, culture has evolved at an astonishing and ever-accelerating rate.
Our aims in this book are to outline the evidence for human anatomical and behavioral evolution before 50,000 years ago and to explore the circumstances surrounding the behavioral revolution that occurred afterwards. One obvious question we must confront at the outset is: what sparked the revolution? Unfortunately, there is no conclusive answer. To attempt one, we must look back at other important biological and behavioral changes that occurred along evolution’s meandering path from our remotest ape-like ancestor to the curious, 01 Twilight.r.qxd 1/29/02 5:03 PM Page 22
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creative reader of this book. Human evolution has followed twists and turns and encountered occasional dead ends. The earliest part of our story still remains rather obscure. This is when some ape-like creature began to walk habitually on two legs. From the time of that pivotal innovation, human evolution can be viewed as a series of at least three and perhaps four sudden and profound events spaced between lengthy stretches of time when little happened.
From Darwin’s day onward, most scientists have perceived evolution as a gradual and cumulative process, a slow, stately unfolding of life’s history. In 1972, however, evolutionary biologists Niles Eldredge of the American Museum of Natural History and Stephen Jay Gould, now at Harvard University, challenged this perspective. They proposed that conspicuous and long-recognized gaps in the fossil record of past life actually provided vital information about the pace and pulse of evolution. As they wrote in a 1972 article, “Many breaks in the fossil record are real; they express the way in which evolution occurs, not the fragments of an imperfect record.” Eldredge and Gould called their hypothesis punctuated equilibrium. Its key idea was that true evolutionary innovations appear suddenly and infrequently. It is at these points of abrupt change, often sparked by major climatic or environmental shifts, that new species tend to arise. Major climatic shifts not only open up fresh ecological opportunities, they also extinguish existing species, clearing the ecological playing field for new ones. Viewed from the present, the fossil record appears to show a sudden inflection after a period of constancy, a species-spawning event captured in a flash of geologic time, which punctuates an otherwise prolonged period of evolutionary equilibrium. In other words, stability is the norm, while speci-ation (the formation of new species) is the rarer but essential exception.
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Evolution, in Eldredge and Gould’s view, resembles a roller coaster ride: slow and steady ascents interrupted by breakneck plunges and curves. Just as the ascents occupy most of the brief roller coaster ride, gradual change comprises most of evolutionary time. But punctuations hold all the action and excitement.
New species probably most often arise in small, isolated populations where genetic changes (mutations) are particularly likely to take hold and become dominant. In large populations or in small populations that are in regular contact with others, genetic changes, even advantageous ones, are more likely to be swamped and to disappear strictly by chance. Each of the three or four punctuation events that we propose led up to the dawn of modern human culture occurred when human populations were small and geographically limited by modern standards. Each apparently occurred in Africa, and on present evidence, each appears to mark a coincidence of major biological and behavioral change. The first event occurred around 2.5 million years ago, when flaked stone tools made their initial appearance. These comprise the earliest enduring evidence for human culture, and their emergence probably coincided closely with the evolution of the first people whose brains were significantly larger than those of apes. The second event took place around 1.7 million years ago. The people this time were the first to possess fully human as opposed to ape-like body proportions, and they invented the more sophisticated stone artifacts that archeologists call hand axes. They may also have been the first to venture out of Africa. The third and most weakly documented event occurred around 600,000 years ago, and it involved a rapid spurt in brain size, together with significant changes in the quality of hand axes and other stone tools. The fourth and most recent event occurred 01 Twilight.r.qxd 1/29/02 5:03 PM Page 24
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about 50,000 years ago and it was arguably the most important of all, for it produced the fully modern ability to invent and manipulate culture. In its wake, humanity was transformed from a relatively rare and insignificant large mammal to something more like a geologic force.
Archeology demonstrates the radical nature and consequences of the last event, but it says nothing about what prompted it, and it is here that we face a conundrum. Arguably, the most plausible cause was a genetic mutation that promoted the fully modern brain. This mutation could have originated in a small east African population, and the evolutionary advantage it conferred would have enabled the population to grow and expand. This is because it permitted its possessors to extract far more energy from nature and to invest it in society. It also allowed human populations to colonize new and challenging environments. Possibly the most critical aspect of the neural change was that it allowed the kind of rapidly spoken phonemic language that is inseparable from culture as we know it today. This ability not only facilitates communication, but at least equally important, it allows people to conceive and model complex natural and social circumstances entirely within their minds.
Some might object that a neurological explanation for the explosion of culture after 50,000 years ago is simplistic biological determinism, a just-so story or a
deus ex machina
explanation for a paleontological paradox. The idea admittedly fails one important measure of a proper scientific hypothesis: it cannot be tested or falsified by experiment or by examination of relevant human fossils. Human brains had reached fully modern size many hundreds of thousands of years earlier, and skulls reveal little about the functioning of the brain under-neath. There is nothing in the skulls of people from shortly before and 01 Twilight.r.qxd 1/29/02 5:03 PM Page 25
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after 50,000 years ago to show that a significant neurological change had occurred. The neurological hypothesis does, however, measure up to one important scientific standard: it is the simplest, most parsimonious explanation for the available archeological evidence. And that evidence, as incomplete and imperfect as it is, is what we must rely upon to reconstruct our evolutionary past.
Other explanations for the origin of modern human behavior hypothesize that some radical social or demographic event sparked a behavioral revolution about 50,000 years ago. These explanations, however, are at least as circular as the neurological hypothesis, because the evidence for the social or demographic change is simply the behavioral revolution they are meant to explain. And they offer no reason for why the momentous social or demographic change failed to occur tens of thousands of years earlier. Nominating a genetic mutation as the cause answers the “why” question. Mutations arise all the time in individuals and populations. Some are harmful, even lethal; most are neutral, conferring neither benefit nor burden. But a few give their possessors an advantage that, however slight, improves their odds in the game of evolution. If this advantage aids in the ability to obtain or process food, to acquire a mate, and to raise offspring to reproductive age, it is likely to spread within a population. The greater the advantage the mutation confers, the more rapidly it will spread, and no one could question the advantage of a mutation that promoted the fully modern brain. By enhancing the brain’s cognitive and communicative capacity, it would have allowed humanity’s external and internal jour-neys of discovery that continue to this day.
Fossil, archeological, genetic, and linguistic evidence all point to Africa as the place where the 50,000-year-old behavioral break-01 Twilight.r.qxd 1/29/02 5:03 PM Page 26
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through occurred. And based on what we know at the moment, only eastern Africa harbored substantial human populations in the interval surrounding 50,000 years ago. Elsewhere in Africa, severe aridity appears to have sharply reduced human populations from 60,000 years ago or before until 30,000 years ago or later. Thus, only east African sites like Enkapune Ya Muto may record the dawn of human culture.
The more certain point, however, is that the dawn did not occur in Europe. Although our concept of early symbolism is inevitably skewed by resplendent European examples like the charcoal rhinoceroses and bears on the walls of Grotte Chauvet or the multicolored bulls and horses of Lascaux, these all postdate the emergence of modern behavior and the arrival in Europe of fully modern humans. Had the crucial mutation occurred first in Europe, the earliest evidence for modern behavior would be there, and students of human evolution today would be Neanderthals marveling at the peculiar people who used to live in Africa and then abruptly disappeared.
Culture provides a uniquely advantageous means for adapting to environmental change. Cultural innovations can accumulate far more rapidly than genetic mutations, and good ideas can spread horizontally across populations as well as vertically between generations.
This strategy of cultural adaptation, more than anything else, has enabled our species to transform itself from a relatively insignificant large African mammal to the dominant life form on Earth. We have developed an unprecedented ability to adapt to a wide variety of environments and, sometimes unfortunately, to alter them irrevocably.
Having acquired this seminal cultural advantage, the earliest fully modern humans were able to disperse from Africa, northwards through the Near East to Europe and eastwards across Asia to China and 01 Twilight.r.qxd 1/29/02 5:03 PM Page 27
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beyond. Because people could now obtain more resources to produce and feed yet more people, population numbers began their long, steep climb to the levels that we now enjoy. Humans colonized new and increasingly challenging environments and began to develop the forms of complex social organization that are both a blessing and a curse today. And the rest, as they say, is history.
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