Mon Jul 18, 2011 10:25 AM ET
discovery.com
Damian Labuda of the University of Montreal's Department of Pediatrics and the CHU Sainte-Justine Research Center conducted the study with his colleagues. They determined some of the human X chromosome originates from Neanderthals, but only in people of non-African heritage.
"This confirms recent findings suggesting that the two populations interbred," Labuda was quoted as saying in a press release. His team believes most, if not all, of the interbreeding took place in the Middle East, while modern humans were migrating out of Africa and spreading to other regions.
The ancestors of Neanderthals left Africa about 400,000 to 800,000 years ago. They evolved over the millennia mostly in what are now France, Spain, Germany and Russia. They went extinct, or were simply absorbed into the modern human population, about 30,000 years ago.
Neanderthals possessed the gene for language and had sophisticated music, art and tool craftsmanship skills, so they must have not been all that unattractive to modern humans at the time.
"In addition, because our methods were totally independent of Neanderthal material, we can also conclude that previous results were not influenced by contaminating artifacts," Labuda said.
This work goes back to nearly a decade ago, when Labuda and his colleagues identified a piece of DNA, called a haplotype, in the human X chromosome that seemed different. They questioned its origins.
Fast forward to 2010, when the Neanderthal genome was sequenced. The researchers could then compare the haplotype to the Neanderthal genome as well as to the DNA of existing humans. The scientists found that the sequence was present in people across all continents, except for sub-Saharan Africa, and including Australia.
"There is little doubt that this haplotype is present because of mating with our ancestors and Neanderthals," said Nick Patterson of the Broad Institute of MIT and Harvard University. Patterson did not participate in the latest research. He added, "This is a very nice result, and further analysis may help determine more details."
David Reich, a Harvard Medical School geneticist, added, "Dr. Labuda and his colleagues were the first to identify a genetic variation in non-Africans that was likely to have come from an archaic population. This was done entirely without the Neanderthal genome sequence, but in light of the Neanderthal sequence, it is now clear that they were absolutely right!"
The modern human/Neanderthal combo likely benefitted our species, enabling it to survive in harsh, cold regions that Neanderthals previously had adapted to.
"Variability is very important for long-term survival of a species," Labuda concluded. "Every addition to the genome can be enriching."
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