A human geneticist explores genetic diversity in Asia.

We often imagine that the heterogeneity of human populations is a reflection of thousands of years of human migration, but there is little evidence to support this. DNA may provide a source of such evidence, particularly that of the people of Asia, which has a population of 3.9 billion and a diverse set of ethnic groups.

Previous studies of Asian migration history and genetic diversity included only a limited number of protein markers and relatively few individuals from each ethnic group. So it was no surprise that the HUGO Pan-Asian SNP Consortium launched an effort to scrutinize Asian genetic variation in more detail. The consortium, made up of dozens of researchers spread predominantly across Asia, analysed the genomes of nearly 2,000 people from 75 ethnic groups. What was surprising was that most of the East Asian haplotypes — patterns of gene variants that co-occur on a single chromosome — were found in either South East Asia or South Central Asia. Moreover, half of these haplotypes were found in South East Asia alone (HUGO Pan-Asian SNP Consortium Science 326, 1541–1545; 2009).

This suggests that this area of the continent was the most probable source of migration to other parts of Asia early in human history. The haplotype diversity is strongly correlated with latitude, and the northward gradient of haplotype distribution points to a possible direction of migration of ancient Asians.

Although the data do not disprove the direction of a second wave of migration that is presumed to have occurred from Africa to Asia, they do indicate substantial dominance of population migration from South East Asia towards other Asian territories. This is an exciting example of genetics providing solid evidence of migration paths, filling in the gaps of human history.

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