Friday, September 04, 2009

Super Y lineages over the past 10,000 years   posted by Razib @ 9/04/2009 03:45:00 PM

Dienekes posted a bunch of abstracts from the 2009 American Society of Human Genetics meeting. This one is of interest in light of recent posts on this weblog:
Some Y-chromosomal haplotypes have been found at unusually high frequencies in Asian and European human populations. The massive spreadof these lineages has been explained by the impact of social selection i.e.the high reproductive success of some males and their relative/descendants due to their high social status. The most well-known examples are the "Khan haplotype" and the "Manchou haplotype" in Asia, and the U’Neill haplotype in Ireland. But are these frequent haplotypes always associated with recentevents of social selection, or could they be linked to much older processes? To address this question, we have surveyed ~ 3500 males in 97 populationsfrom Turkey to Japan. We have focused on the 12 most frequently represented haplotypes in Eurasia and tested whether their expansions are linked to a specific factor such as language or subsistence methods. Our results show that both recent and ancient processes are responsible for the expansions of these lineages. The recent expansions (2000-3000 years) likely to be linked to social selection are prevalent in Altaic-speaking and pastora lpopulations. This might indicate a recent cultural change in the social organizationof these populations. The ancient expansions (8000-10000 years) are over-represented in Indo-European speaking and sedentary farmer populations,and are likely to be the result of the Neolithic transition.

Asymmetries between male and female lineages are always of interest. For example, diversity of Y and mtDNA correlates well with patrilocality vs. matrilocality. The idea of "super-male" lineages was mooted by Bryan Sykes several years ago in the wake of the "Genghis Khan haplotype", though it benefited from particular preconceptions many have about the nature of male genetic reproductive fitness. But it is likely that these dynamics vary by population due to ecological and/or social parameters. The time window for the expansion of Y lineages among Altaic speakers is very suggestive in light of historical records and archaeological data. It seems that early on (i.e., before 500 BCE) horse-based nomadism was dominated by Indo-Europeans, predominantly Iranians, in Eurasia. In the few centuries before Christ the populations of the eastern steppe, the precursors of Altaic language families, adopted this lifestyle, and to a great extent superseded the Iranian populations across the length and breadth of the non-sedentary zone over the next 1,500 years (the fact that the Ossetians are now a people who reside in the Caucasus is illustrative of the great retreat of Iranian peoples on the steppe). I have suggested that there is a winner-take-all dynamic in regards to steppe polities, and I suspect this will be reflected in the genetics of male lineages as well.

* It is notable that Ireland was to a great extent a pastoralist society during the period of domination by the Ui Neill .

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