My favorite "toggle" story has toggled again. Just when it seemed established that Neanderthals and modern humans did the nasty before the heavy-browed hominids went extinct, a study now suggests that the DNA modern Europeans and Asians share with Neanderthals may trace back to the mists of time in Africa, not to more recent encounters between the two differentiated species in Eurasia.
The question of whether Neanderthals and modern humans "did it" has been a matter of debate for decades. But it seemed to have been resolved in 2010 when it was determined that modern Europeans and Asians -- but not modern Africans -- shared between 1 and 4% of their DNA with Neanderthals, who died out as a distinct species 40,000 years ago.
The interpretation of that data was that modern humans from the "Out of Africa" migration (estimated to have occurred 60,000 years ago) met up with their very distant cousins the Neanderthals and swapped genes. A similar "introgression" may have occurred in Asia between modern humans and mysterious hominids known as the Denovisians. Most recently, anthropologists have theorized that some modern humans in Africa also connected relatively recently with long-lost evolutionary cousins.
But now anthropologists at the University of Cambridge have engineered a computer simulation that suggests another explanation for the DNA overlap between modern Asians and Europeans and Neanderthals. According to this model, the common DNA can be traced back hundreds of thousands of years to a common African ancestor, not to recent "hybridization" in Eurasia.