Friday, August 24, 2012

Science News: Tangled Roots

Bruce Bower of Science News has written a great column that highlights all of the current discoveries/revelations/uncertainties in modern human origins research. The article focuses on the new developments in genetics that have revealed mating patterns between Neandertals and modern humans and the existence of the third strand of humanity, the Denisovans. It is modern human origins research in a nutshell. He writes:
The question is no longer ‘When did ancient populations such as Neandertals go extinct?’ but ‘What happened to those populations and to modern humans as a result of interbreeding?’ ” says anthropologist John Hawks of the University of Wisconsin–Madison.

Clear signs of interbreeding have left archaeologists and other students of the Stone Age scrambling to revisit existing ideas about Homo sapiens’ evolutionary past. A dominant theory holding that humans evolved in Africa and left on neat one-way routes to Asia and Europe has to be revised. Instead, these ancient people must have followed a tangled web of paths taking them to other continents and sometimes reversing course. During these travels, humans encountered Neandertals, Denisovans and probably other humanlike populations that were already traipsing interconnected avenues through Asia and Europe.
Even though it seems likely that modern humans as a whole, owe their ancestry to these African populations, it is gratifying to see genetic evidence in support of what some of us have been hanging onto for all these years—some variant of the multi-regional evolution model. I don't think that a strict center/edge model will work but it is obvious that there was considerable interbreeding between population groups, be they Neandertals, moderns or Denisovans. More and more, everyday, it looks my former adviser, Fred Smith, was right. Some form of assimilation seems to be the best model to go with.

I am also reminded that, once upon a time, Geoff Pope argued that there were traces of Neandertal characteristics in some of the Chinese archaic Homo sapiens material. If, as John Hawks remarks, Neandertals interbred on a grand scale, then Pope's position, which was largely rejected at the time, has some credence.

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