What Happened to the Neanderthals?

Transcription

1 What Happened to the Neanderthals? July 21, 2012 Chipwalter It s one of the great mysteries of human evolution the disappearance of the Neanderthals, a species of remarkable primates who lived and hunted the mountains and vast plains of Europe and Asia for 200,000 years until one day, some 25,000 years ago, they were gone. ancestors, the Cro-Magnon people. For 150 years scientists have worked up theory after theory to explain their demise; the most prevalent being that they were done in by their own shortcomings lack of brains, lack of tools, lack of speech with some generous help from our Homo sapiens It s easy enough to come to that conclusion if you buy into the popular view that Neanderthals were dumb brutes sitting somewhere along the evolutionary chain between a Harry Potter troll and the wrestlers in the WWF. The term Neanderthal itself is a synonym for mean, big and stupid. But the story of how they met their end is a good deal more complicated than all that, and considerably more mysterious. It s now clear that though they lived under brutal and unforgiving circumstances, they were themselves neither brutal nor stupid. In fact their brains were slightly larger than ours are today, and their accomplishments remarkable. They managed to survive not one, but three ice ages. The bones of over 400 Neanderthals have been unearthed going back almost 100 years revealing that at one time or another clans were living as far west as the Iberian Peninsula and as far east at the Altai Mountains in Southern Siberia. When the weather grew colder they ventured as far south as the Arabian Peninsula and Gibraltar, and when glaciers receded they receded with them to the mountain ranges of northern Europe. There is no evidence that they ever made their way to Africa, something that makes sense. Their bodies were optimized for the cold, and over the past 200 millennia there was plenty of that in Europe and their haunts in Asia. But if they were so clever and so hardy, why did they fail? Here are three theories. Theory One: Murder Most Foul: The story goes this way. The Cro-Magnon people, our direct ancestors (named, like Neanderthals, for the location in Europe where the first of their fossils were discovered),

2 systematically wiped their burly cousins out. To be clear, the Cro- Magnon were us, anatomically modern humans, who migrated north from Africa 40,000 to 50,000 years ago. When we crossed paths, hunting grounds and choice settlements were at stake, and so the Cro-Magnon, with their superior weapons, and possibly their superior planning skills, killed or enslaved whomever was unfortunate enough to get in their way. It wouldn t have been an all out war in the sense that armies were assembled and clashed, but the damage done to the Neanderthal would have been inexorable with one settlement, tribe or clan after another falling to the new intruders. There s not much evidence for warfare or murder in the fossil record, however. We haven t found ancient killing fields, strewn with the hacked and broken bones of the two human species; no sites where dead Homo sapiens lie next to the skeletons of Neanderthals. But then, maybe, the evidence of battles between competing tribes of the two peoples simply hasn t deigned to show its archaeological face. Maybe, somewhere in Europe, in a remote mountain forest or beneath a broad river re-routed by the last retreating glaciers lie the bones of lost prehistoric warriors who fell to the invaders from the southern seas. But so far, no such evidence has been found. Theory Two: Survival of the Fittest. A second theory is that we out competed the Neanderthal for resources, food and land. The thinking here is we didn t murder them hand to hand and face to face, we wiped them out them in a long war of attrition by taking control of the best habitats and hunting grounds, and then killing game faster than they could, and in larger numbers. Very slowly, over thousands of years, we drove the already sparse and scattered Neanderthal population into pockets where it became increasingly difficult for them to survive. This might have crippled their ability to band together, weakening them still further, until in the end they simply couldn t go on.

3 There is some evidence for this. Neanderthals did become progressively rare as Europe moved into the coldest phase of the last ice age and as modern humans migrated into Europe. Leslie Aiello of University College London suggests that even though Neanderthals were well adapted to frigid climates, they couldn t survive temperatures below 0 F. (-18 C.) Their clothing and technology simply weren t up to it. 30,000 years ago, as temperatures dropped and a new ice age descended, warm pockets of land would have become more scarce. If the Neanderthals retreated to them they may have been trapped and died as these locations themselves grew increasingly cold. It wouldn t be the first time one species snatched an ecological niche from another. In fact today we continue to wipe out species all around the planet, not as part of a master plan, but simply by doing what we do and living as we live. Nevertheless, Europe and Asia are immense territories, and it s difficult to imagine that there wouldn t have been enough resources to go around. Neanderthal ranges covered millions of square miles. While each clan probably needed several square miles of land to sustain them, much of the land was rich with food and resources and herds of large animals like mammoths and woolly Hippopotamuses, deer and bison. Even if the combined numbers of both species reached into the hundreds of thousands, there would seem to have been plenty of space and food and resources to go around. The cold weather could certainly have battered Neanderthals trapped in cold areas, but why wouldn t those already living in southern Italy, Spain, France and the Mideast have survived? Theory Three: Love and Lust. The most intriguing Neanderthal disappearance theory is that if we killed them at all, we killed them with kindness. We neither murdered them, nor outcompeted them. We mated with them and, in time, simply folded them into our species until they disappeared, swallowed up in the larger Homo sapiens gene pool. This may explain the origins of the red hair, light skin and freckles some of us sport. Neanderthals, unlike the slim, dark skinned interlopers from the south, would have evolved fairer complexions and lighter hair as a way to extract more vitamin D from the stingy sun of cold, northern latitudes. Spreading these genes around may even have benefited the Cro- Magnon. It s fascinating to consider the possibility that we and another kind of human bred a new third variety. Whether this happened or not is one of the great controversies in paleoanthropology. But there is evidence. Recently very strong evidence. In 1952 an armful of bones belonging to an adult woman were found lying on the floor of a Romanian cave a leg bone, a cranium, a shoulder blade and some other fragments. The

4 discoverers didn t think much of the find at the time. How old could the bones be, after all, if they were simply strewn there on the surface of the cave s interior. And so they were relegated to a drawer where they lay undisturbed for more than half a century. When a team of researchers from the United States finally began to inspect the old findings, radio carbon dating revealed the woman hadn t lived very recently at all, but last walked the Earth 30,000 years ago. Not only that, but the bones exhibited features that were both Cro- Magnon and Neanderthal. The back of the woman s head, for example, protruded with a Neanderthal-like occipital bun, her chin was unusually large and her brow more sloped than any belonging to a modern human. There have been other similar finds that raise the interesting possibility that we and our bigboned relatives developed more than Platonic relationships. There is the skeleton of a young boy uncovered in Portugal that dates to 24,500 years ago. He is believed to be Neanderthal with a large jaw and front teeth, foreshortened legs, and a broad chest and, yet his chin is square, more like ours and his lower arms were smaller than you might expect. And in another cave in France, scientists have found, not bones, but tools that date back 35,000 years. The location of the tools indicate that for at least 10,000 years both Cro-Magnon and Neanderthals coexisted in this same place. If they could do that, and if they could communicate and cooperate, isn t it likely they also mated?a modern human. And the woman s shoulder blade, her scapula, was narrow, not as broad compared with ours, another Neanderthal trait. Was she simply a rugged looking modern human, or, as one scientist put wryly it, proof that moderns were up to no good with Neanderthal women behind boulders on the tundra. Strangely enough, this was one of the last areas of Europe where Neanderthals lived before they disappeared. Were they dying out, or was this boy simply archaeological proof that Neanderthals had at last been genetically subsumed into the rising tide of modern humans spreading across the planet? Maybe. Now there s genetic evidence that we today are a hybrid species. Just last year a scientific consortium headed by the Max Planck Institute for Evolutionary Anthropology completed an analysis of the Neanderthal genome. They compared the ancient DNA with the genomes of five living people of different lineages French, Han-Chinese, Papuan and members of the Yoruba and San people of Africa. The San are, genetically, among the most ancient modern humans on earth. They found that all the genomes from every part of the world except Africa contained 1 to 4 percent Neanderthal DNA. In other words, most of the human race from Europe to the islands of Southeast Asia (and probably farther) are part Neanderthal. What is perplexing about the find, however, is that this DNA test indicates that the Cro-Magnon and Neanderthals mated between 50,000 and 80,000 years ago, before they met in Europe. Whether they mated later in subsequent encounters remains unresolved, for now. So which way did the hardy and quiet white people of the North meet their end? Murder, competition, love? There is no reason why it has to be any one of these. Nature, evolution and human relations are all chaotic and unpredictable as much as we might like it otherwise. When Europeans colonized north and south America, they sometimes befriended the natives, sometimes brutally exterminated them, sometimes raped their women and sometimes fell in love and raised families. Given the nature of human nature, our encounters probably included all of the above. Were the Neanderthal so different from the Cro-Magnon that sex was out of the question? Not likely. Both species were human and the drive to procreate is strong and primal.

5 Surely there were Romeos and Juliets, even this far back in our history, who found enough common ground during those long, wintry millennia to bed down together. And as a result, nearly all of us can say we have a little Neanderthal in us. Task: 1. use the graphic organizer to take notes on the three theories 2. write a paragraph explaining which theory you think is the best and why? Theory 1 Theory 2 Theory 3 Main Idea Evidence to support Problems with theory

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