For the last couple of decades the human evolution debate has been dominated by the “Out of Africa” theory, which holds that Homo sapiens evolved in Africa around 200,000 years ago, then began spreading to other continents at around 60,000 to 70,000 years ago. This theory has developed from analysis of human DNA, i.e., from the study of our genetic makeup.
The Out of Africa theory has been opposed by another called “multiregionalism,” which proposes that the much older ancestor of Homo sapiens, Homo erectus, as well as subsequent evolutionary developments such as Homo neanderthalensis, were all the same species, but had evolved gradually over about 2 million years and all over the world — albeit with some regional adaptations/differences — into Homo sapiens. Rather than DNA, multiregionalists have relied upon fossil evidence, noting especially regional similarities between bones of erectus and later sapiens.
Though multiregionalism still has its adherents — and the debate has often been filled with acrimony from both sides — the Out of Africa theory for the origins of modern humans has emerged as the dominant paradigm. Thus, it has generally come to be believed that we all — regardless of ancestry, whether European, Asian, African, etc. — can trace our roots to an “African Eve” of comparatively recent origin.
One caveat in the debate which remained unresolved was whether or not Homo sapiens might have bred with Homo neanderthalensis, with whom they overlapped and had contact between about 100,000 and 30,000 years ago, when the last of the Neanderthals disappeared. For, if modern humans and Neanderthals bred together — i.e., there was “gene flow” — then there is at least some basis for the multiregionalist position for gradual evolution as well as also the possibility of regional genetic differences in populations of modern Homo sapiens.
And evidence of gene flow is precisely what an extremely important study of Neanderthal DNA appearing in the current issue of the journal Science has found.
To very briefly summarize, researchers at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, using DNA samples from the bones of three Neanderthals found in Croatia, have recently succeeded in mapping a good bit of the Neanderthal genome (around 60%). And when they compared Neanderthal DNA to that of a small group of modern humans with different ethnic backgrounds, they found a genetic contribution of Neanderthals to non-Africans (specifically Europeans, Asians and New Guineans) of 1-4%.
As you might expect this is a very controversial finding, because, as a New York Times report on the findings put it, it “would mean that non-Africans drew from a second gene pool not available to Africans.” Though the Leipzig study does not exactly refute the Out of Africa theory, some modifications will at the very least be in order — as long as the findings hold up.
And for a person of European ancestry like myself, I suppose I’ll just have to get used to a “Neanderthal Eve” in my distant past, in addition to my African one. Well, I’ve always kind of liked Neanderthals anyway. So, that’s OK by me.
If you’re interested in reading more on human origins, check out some titles from Greensboro Public Library listed in this previous post.
Filed under: Science, Uncategorized | Tagged: DNA, Homo neanderthalensis, Homo sapiens, human evolution, modern human origins, multiregionalism, Neanderthal genome, Neanderthals, Out of Africa Theory | 6 Comments »