Chinese anthropologists say they have found strong evidence that the Uygurs are a genetic mix of both East Asian and European ancestries, challenging a study suggesting the Uygurs are genetic ancestors of the East Asian gene pool.
Xu Shuhua, leading author of the paper published in the online version of Molecular Biology and Evolution, a journal published by the Oxford University Press, said their study showed the Uygurs are not the source population of East Asian peoples.
A paper written by three scholars from the United Kingdom's Oxford University and published in PLoS Genetics in May 2008 suggested East Asians had a genetic source entirely distinct from European peoples. The Uygurs and Hazara gave rise to Cambodian, Mongolian, Oroquen, Xibo, Yi, Tu, Daur and Naxi people of East Asia.
"Our study shows that the Uygur population is more likely a sole recipient with contributions from both East Asian and European peoples," Xu said Wednesday at a session on molecular anthropology at the 16th congress of the International Union of Anthropological and Ethnological Sciences (IUAES).
Xu, ageneticist of the Chinese Academy of Sciences and Max Planck Society Partner Institute for Computational Biology, together with Dr. Jin Wenfei and Dr. Jin Li, analysed the genetic structure of Uygur samples collected in Yili, in northern Xinjiang Uygur Autonomous Region and Hetian in southern Xinjiang Uygur Autonomous Region.
They compared 20,177 single nucleotide polymorphisms (SNPs) -- a DNA sequence variation occurring in specific populations -- from their own samples and 650,000 SNPs from public genome-wide data to identify shared chromosomal segments between populations.
The study showed that the Uygur were formed by a two-way mixture, with 60 percent European ancestry and 40 percent East Asian ancestry, that occurred about 2,000 years ago.
Xu explained that if a population had substantial genetic variations that overlapped with that of two other populations, then there are two possible hypotheses: the Uygurs could be the donors of the East Asian and European populations or they could be the recipients.
The rationale of the analysis was that the genetic changes increased the extent of differences among population and the longer the time, the bigger the differences and the smaller the similarities.
If the Uygurs were ancient genetic donors to the East Asian and European populations, they should have distinct haplotypes -- sets of inherited, linked genetic markers, Xu explained. If the Uygurs were a mixed population, they were expected to have few distinct haplotypes.
"Our results showed that more than 95 percent of the Uygur haplotypes could be found in either East Asian or European populations, which contradicts the expectation that the Uygurs are donors," said Xu.
He said the simulation studies further indicated that the proportion of unique Uygur haplotypes observed in empirical data best matched the assumption that they are an admixture population.
According to anthropologists, the Uygurs are a group of people primarily residing in Xinjiang, China, in Central Asia, from where modern humans presumably spread, reaching Europe, east and northeast Asia about 40,000 years ago.
"Although the history of Uygurs could be complex, our method is explicit and conservative in rejecting the 'donor' hypothesis," Xu said.
Han Kangxin, a Chinese archeologist who studied skulls unearthed in Xinjiang believes the main ancestry of the Uygur population is Caucasoid. "There is also hypothesis that the Uygurs are an mixture of the Causasoid and Mongoloid, but it is not a final conclusion," Han said.
The IUAES, being held in Kunming, runs until Friday, July 31.
(Xinhua News Agency July 30, 2009)
