After examining the DNA of an ancient European man, researchers have discovered that modern humans were mating with Neanderthals right up until the time they became extinct, around 30,000 years ago. This is much more recent than previously believed. This surprising finding was presented at the Biology of Genomes meeting last week.
When our ancestors left Africa and entered the rest of the world, they were not pioneers. What they found was a landscape populated by at least two other species of human, both of which had been living on the plains and steppes of Europe and Asia for a few hundred thousand years. It has now become clear that when these three populations of hairless ape met, which they seemed to have done not infrequently, things weren’t always hostile.
What researchers realized after sequencing the Neanderthal genome was that they shared more in common with Europeans than they did with Africans. This suggests that when modern humans met Neanderthals in Europe, sometimes they were lovers more than fighters. The previous estimate that people outside of Africa have up to 4% of Neanderthal DNA within them has since been revised down to about 2%.
But it didn’t stop there. When modern humans trekked out across Asia, they found yet another species of ape living and hunting in the landscape. Only known from a couple of finger bones and a few teeth found in a cave in Siberia in 2010, it seems that the Denisovans were another distinct species. Incredibly, further DNA analysis in 2011 found that significant amounts of Denisovan DNA survives in Southeastern Asian and Oceanian populations.
There seems little doubt then that on their exodus out of Africa, modern humans met, interacted, and in at least some cases mated with other species of humans. The question that remains and is hotly debated, however, is how often did this happen?
Last year, researchers at Harvard University conducted DNA analysis on a bone discovered in a cave in Northern Spain. Due to its age and geographic location, they presumed it would be from a Neanderthal. What they actually found surprised them—the bone was more closely related to the Denisovans. This raised the possibility that there was a lot more interaction and movement between the different species and populations than previously thought.
The same team ran another analysis on the modern human bones of a man found in Romania who lived about 40,000 years ago, about the time at which the Neanderthals were on their way out. They reported this year that they found he was up to an amazing 11% Neanderthal. From this, they were able to calculate that he had a Neanderthal relative four to six generations back.
This goes against one of the previously held beliefs that they only mated early on when the two species first met in the Middle East and suggests, says Qiaomei Fu, one of the researchers from Harvard, that both species were meeting and mating for the whole period in which they were coexisting, about 20,000 years in total.
Top image: Erich Ferdinand / Flickr CC BY 2.0