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Before calling someone a Neanderthal, take a moment and think about this: You may be one yourself - or at least you may have Neanderthal ancestors. That's the conclusion of a study being released today. Researchers examined DNA extracted from bones that are more than 35,000 years old.
The study should end a long-running debate about whether modern humans did more than simply coexist with Neanderthals before our hominid cousins were extinct.
NPR's Joe Palca has our story.
JOE PALCA: It's extremely likely that modern humans and Neanderthals bumped into each other once upon a time.
Professor DAVID REICH (Geneticist, Harvard Medical School): The archaeological record shows they overlapped between about 30 and 80,000 years ago.
PALCA: David Reich is a geneticist at Harvard Medical School. There's some fossil evidence that they may have done more than shake hands in passing, but the initial genetic evidence suggested otherwise.
Prof. REICH: And so the big open question was whether they exchanged genes during that time when they overlapped in the Middle East and in Europe.
PALCA: We're not talking about exchanging genes as an exchanging trading cards. We're talking about had sex together?
Prof. REICH: That's right. That's right.
PALCA: I'm glad we cleared that up. As hard it may be to believe, fragments of DNA can survive in bones more than 30,000 years old. And scientists from the Max Planck Institute in Leipzig, Germany, have now completed a draft sequence of the three billion letters of Neanderthal DNA.
Modern humans moved out of Africa about 80,000 years ago, after Neanderthals had already settled in Europe and elsewhere. So if Neanderthals contributed genes to modern humans, it would have been after those humans had left Africa.
So Reich compared Neanderthal DNA with modern African and non-African DNA and found that the non-African DNA was more related.
Mr. REICH: The non-African, like, is more closely related to the Neanderthal, quite definitely, highly statistically significantly overwhelming evidence that they're more closely related on average to Neanderthals.
PALCA: In other words, Reich and his Leipzig co-authors are totally sure that Neanderthal genes found their way into modern humans when the two species intersected. They report their findings in the journal Science.
Mr. REICH: The simplest possible explanation is that it occurred once, but it very easily could have occurred on multiple occasions, and perhaps it's likely that it occurred on multiple occasions.
PALCA: Reich says it's hard to pin down exactly how much DNA Neanderthals contributed to modern humans.
Mr. REICH: We estimate about one to four percent of the genetic ancestry of non-Africans is from Neanderthals.
PALCA: And just to be clear: Reich says there's no stigma to have a bit of Neanderthal heritage.
Mr. REICH: Absolutely not, and in fact, people who have Neanderthal DNA have done just fine in our society.
PALCA: Now that they have the sequence, scientists can start looking for regions of DNA that differ between Neanderthals and humans, the genetic stuff that makes us us.
Mr. RICHARD GREEN (Geneticist): And then, once the regions are identified, look to see, well, what genes are here, what biological sense can we make of this?
Richard Green recently left Leipzig to join the faculty of the University of California, Santa Cruz. He says they've already begun to identify genes that have changed during human evolution.
Mr. GREEN: Which one of these happened very recently, since we split even from Neanderthals, and which ones of these are much older and happened in the six million years or so since we diverged from chimpanzees?
PALCA: Already, the Neanderthal DNA has shown that genes involved in wound healing, sperm swimming and hair shape have all changed fairly recently.
Having the Neanderthal sequence is like having a totally new perspective on ourselves. John Hawks is an anthropologist at the University of Wisconsin. Hawks says it's like the first time humans were able to look back at the Earth from beyond Earth's orbit.
Mr. JOHN HAWKS (Anthropologist, University of Wisconsin): We can say: Here's a picture of what we are from the outside, from the distant past. And we can use that to get a new picture of what we are. It's amazing. I mean, it is really -can't express how I feel this morning.
(Soundbite of laughter)
Mr. HAWKS: It's really cool.
PALCA: An exciting time to be a modern human anthropologist studying human origins. Joe Palca, NPR News, Washington.