"Confirmed": all non-Africans are part Neanderthal

Some of the human X chromosome originates from Neanderthals and is found only in nonAfricans, a new study concludes.

"This confirms recent findings suggesting that the two populations interbred," said researcher Damian Labuda of the University of Montreal, whose work with colleagues is published in the July issue of the journal Molecular Biology and Evolution.

Neanderthal people, whose ancestors left Africa about 400,000 to 800,000 years ago, evolved in what is now mainly France, Spain, Germany and Russia, and are thought to have lived until about 30,000 years ago. Meanwhile, early modern humans left Africa about 80,000 to 50,000 years ago. The question has been whether the physically stronger Neanderthals, who had the gene for language and may have played the flute, were a separate species or could have interbred with modern humans.

The results show that the two lived in close association, probably early on in the Middle East, Labuda said. "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 and his team almost a decade ago identified a piece of DNA, called a haplotype, in the human X chromosome that seemed different and whose origins they questioned. When the Neanderthal genome was sequenced in 2010, they compared 6,000 chromosomes from all parts of the world to the Neanderthal haplotype. The Neanderthal sequence was present in peoples 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. This is a very nice result, and further analysis may help determine more details," said Nick Patterson of the Massachusetts Institute of Technology and Harvard University, a human ancestry researcher who was not involved in the new study.

"Labuda and his colleagues were the first to identify a genetic variation in nonAfricans 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," said David Reich, a Harvard Medical School geneticist, one of the principal researchers in the Neanderthal genome project.

So did these exchanges contribute to our success across the world? "Variability is very important for longterm survival of a species," said Labuda. "Every addition to the genome can be enriching."

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