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About two weeks ago, I blogged on how variation mtDNA was used to reconstruct an idea of Pleistocene population growth. That study was very remarkable because illuminated a large 5 fold increase in South Asian populations about 50,000 years ago. But we haven’t been able to use polymorphisms in autosomal loci to the same. A new paper in Molecular Biology and Evolution tries to figure out a way to overcome this limitation, by testing to see whether or not mitochondrial and Y chromosomal DNA show similarities in the spread of polymorphisms in populations that have experienced a recent increase in effective population size.

The paper, “Contrasting Signatures of Population Growth for Mitochondrial DNA and Y Chromosomes among Human Populations in Africa,” honed in a large sequence from the Y-chromosome and the cytochrome c gene in the mtDNA from 172 males from 5 African populations. Four different statistical tests were applied to test for population expansion: Fu’s Fs statistic, the R2 statistic, coalescent simulations, and the mismatch distribution.

The authors find,

“…Patterns of mtDNA polymorphism better fit a model of constant population size for food-gathering populations and a model of population expansion for food-producing populations. In contrast, none of the tests reveal evidence of Y chromosome growth for either food-gatherers or food-producers. The distinct mtDNA and Y chromosome polymorphism patterns most likely reflect sex-biased demographic processes in the recent history of African populations. We hypothesize that males experienced smaller effective population sizes and/or lower rates of migration during the Bantu expansion, which occurred over the last 5,000 years.”

    Pilkington, M.M., Wilder, J.A., Mendez, F.L., Cox, M.P., Woerner, A., Angui, T., Kingan, S., Mobasher, Z., Batini, C., Destro-Bisol, G., Soodyall, H., Strassmann, B.I., Hammer, M.F. (2008). Contrasting Signatures of Population Growth for Mitochondrial DNA and Y Chromosomes among Human Populations in Africa. Molecular Biology and Evolution, 25(3), 517-525. DOI: 10.1093/molbev/msm279