Central Asia is a vast region at the crossroads of many cultures linked by ancient trade routes and habitats. Little is known about the genetics and the history of the population of this region. But a recent study proposes two hypotheses.

Although studies of the human Y chromosome support the idea the region is an important reservoir of genetic diversity of modern humans after they left the African continent, mitochondrial DNA (mtDNA) research also suggests that the peoples of Central Asia might be the result of the genetic admixture of the West and East. The mitochondrial DNA has been widely used by biologists over the past 15 years as a powerful tool to trace the evolutionary history of a species.

However, due to the lack of adequate mtDNA data and their interpretation methodology, the admixture theory has been until recently far from convincing.

But a recent mtDNA study by researchers from the Chinese Academy of Sciences (CAS) has shed new light on the origin of the Central Asian population by adding new evidence to the admixture hypothesis, according to the information office of the CAS.

The research work was reported in the August issue of the Molecular Biology and Evolution.

Zhang Yaping and his colleagues from the Kunming Institute of Zoology under CAS analyzed 252 mtDNAs of five ethnic groups (Uygur, Uzbek, Kazak, Mongolian, and Hui) from Xinjiang Uygur Autonomous Region in northwest China, where once ran the ancient Silk Road, together with some reported data from the adjacent regions in Central Asia.

The researchers classified the mtDNAs into different groups according to the available evolutionary information, and compared their frequencies to show the differences among the genetic structures of these populations along the maternal line with different demographic histories.

The results highlight that most of the mtDNA types identified, belonged to defined gene pools of either eastern or western Eurasian. Therefore, their findings provide direct evidence to support the suggestion that Central Asia is "a melting pot" for the genetic admixture of the East and the West.

The research also observed a decreasing tendency of the western Eurasian-specific genetic group frequency, with the highest frequency present in Uygur and Uzbek, followed by Kazak, Mongolian and Hui.

In addition, the research shows that many factors such as ethnical origin, marriage customs and economic development exert important influences on the maternal structure of different communities in Xinjiang.

(China Daily September 23, 2004)