We've known for a while that some Neanderthals and early modern humans mated; most of us still carry a small percentage of Neanderthal DNA (which may have some ill effects on us). But when exactly did that mating take place? An article, published in the journal Nature, suggests that interbreeding between humans and Neanderthals began 100,000 years ago. This extends the previously accepted timeline by 40,000 years, the BBC reports.

For the study, the scientists used the genome of a female Neanderthal who was discovered in a remote cave in the mountains of Siberia. While Neanderthal DNA found in modern humans supports the idea that the two groups met during migration out of Africa between 47,000 and 65,000 years ago, the presence of human DNA in the Neanderthal woman adds an earlier encounter to the narrative. That evidence may change what we knew about when migration out of Africa started and where early modern humans went.

"We conclude that in addition to later interbreeding events, the ancestors of Neanderthals from the Altai Mountains and early modern humans met and interbred, possibly in the Near East, many thousands of years earlier than previously thought," the scientists wrote.

Paleoanthropologist Chris Stringer of the Natural History Museum in London, who was not involved in the study, told the BBC that experts still aren't sure exactly where those interbreeding events took place. "We really don't know how widespread Neanderthals and early modern humans might have been in the regions between Arabia and China at this time," he said.

Stringer added that scientists are also unsure about the nature of the events or whether they were even consensual. One way to tell the difference would be to determine if human DNA was transferred solely from males to females or if there was a balance. Stringer says a lot more data is needed to determine that.

[h/t BBC]