We know that modern humans mated with Neanderthals at some point in history, and now we could have a better idea of when, thanks to DNA analysis of a 45,000-year-old femur bone.
The bone was originally found six years ago by an ivory carver in Siberia and is, so far, the oldest human bone found outside of Africa and the Middle East. After scientists analyzed the DNA of the bone, they realized that it also has the oldest Homo sapiens genome sequence we currently have on record.
"It's really exciting that we now have a really high-quality genome sequence of an early modern human that is this old," says study author Janet Kelso of the Max Planck Institute for Evolutionary Anthropology.
Previous studies of DNA in modern humans has shown that for humans born outside of Africa, at least 2 percent of their DNA is Neanderthal. But as to when the two species began mating was, up until now, still a bit of a mystery.
Neanderthals were our ancestors, from the Stone Age, and died out around 30,000 years ago. In the Middle East, they existed with modern humans as long as 100,000 years ago. Because of this new DNA evidence, scientists believe that mating between the two species started between about 50,000 and 60,000 years ago. Previous studies thought it was much earlier, at over 80,000 years ago.
This find provides more evidence that Neanderthals did not simply just die out, but that Homo Sapiens absorbed them into their larger population through interbreeding.
The age of the fossil itself also paints a picture of the first hunter-gatherers of Siberia, those Homo sapiens that eventually populated Europe and Asia. However, this ancient man's DNA shows that he was not a direct ancestor to us humans living today. Scientists believe he belonged to a group of Stone Age people that died out during an ice age.
However, this find is just one of many, and future similar fossils in the area could exist. Scientists aren't presently ruling out any theories, especially when other fossils suggest that modern humans left Africa before 100,000 years ago and arrived in Asia more than 75,000 years ago.
"This is just a random find in a Siberian river deposit," says Chris Stringer, a paleoanthropologist at London's Natural History Museum. "What else could be there when they start looking systematically?"
