Here we go again. It’s been barely two years since a breakthrough study found that people living outside Africa shared up to 4% of their DNA with Neanderthals, prompting speculation that there had been quite a bit of, shall we say, interspecies intimacy during the 15,000-year period when the two species co-existed in Europe. Now, scientists at the University of Cambridge have proposed that these genetic similarities might instead stem from both species sharing a common ancestor.
In the latest study, evolutionary biologist Andrea Manica and Anders Eriksson used computer simulations to examine the case for inter-species mating, otherwise known as hybridization. They published their sensational findings in on Monday in the journal Proceedings of the National Academy of Sciences.
In a statement reported by the Daily Telegraph, Dr Manica said: “To me the interbreeding question is not whether there was hybridization but whether there was any hybridization that affected the subsequent evolution of humans. I think this is very, very unlikely.”
“Our work shows clearly the patterns currently seen in the Neanderthal genome are not exceptional, and are in line with our expectations of what we would see without hybridization,” he added. “So, if any hybridization happened then it would have been minimal and much less than what people are claiming now.”
In short, our Homo sapiens ancestors probably got it on with their Neanderthal cousins, but not to any great degree — and certainly not enough to so strongly affect our genetic makeup.
The story, according to Manica and Eriksson, actually began half a million years ago, during the existence of a common ancestor to the Neanderthals and Homo sapiens. Roughly 300,000-350,000 years ago, the species diverged between those who migrated North, ultimately evolving into the Neanderthals, and those who moved south, from whom modern humans emerged. It was not until 60,000-70,000 years ago that we humans began to expand from Africa.
As for why some humans more closely resemble Neanderthals than do others, Dr Manica, stressed “common ancestry” and “geographical differences” over hybridization. “The idea is that our African ancestors would not have been a homogeneous, well-mixed population but made of several populations in Africa with some level of differentiation, in the way right now you can tell a northern and southern European from their looks,” he explained.
“Hopefully, everyone will become more cautious before invoking hybridization, and start taking into account that ancient populations differed from each other probably as much as modern populations do.”
Within the academic community, not everyone’s convinced just yet. Professor Svante Pääbo of the the Max Planck Institute for Evolutionary Anthropology, who led the 2010 research, admitted to the Guardian that he was surprised that the study refuting his work had been published and has himself co-authored a new paper, currently awaiting peer review, that adds credence to his original thesis. Meanwhile, Harvard University’s Professor David Reich, a key proponent of the hybridization explanation, told the BBC, “the patterns observed [in our analyses] are exactly what one would expect from recent gene flow.”
It looks like we’ll be talking about human-Neanderthal love for some time.
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