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July 18, 2011

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“Confirmed”: all non-Africans are part Neanderthal

July 18, 2011
Courtesy of the University of Montreal
and World Science staff

Some of the hu­man X chro­mo­some orig­i­nates from Ne­an­der­thals and is found only in non-Af­ri­cans, 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.

Artist's concept of a Neanderthal. (Courtesy Science)
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 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,” 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 long-term sur­viv­al of a spe­cies,” said La­bu­da. “Every ad­di­tion to the ge­nome can be en­rich­ing.”

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Some of the human X chromosome originates from Neanderthals and is found only in non-Africans, 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. His team places the timing of such intimate contacts and/or family ties early on, probably at the crossroads of the Middle East. Neanderthals, 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, 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 this study. “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,” 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 long-term survival of a species,” said Labuda. “Every addition to the genome can be enriching.”