Journal Article

Can a Sex-Biased Human Demography Account for the Reduced Effective Population Size of Chromosome X in Non-Africans?

Alon Keinan and David Reich

in Molecular Biology and Evolution

Published on behalf of Society for Molecular Biology and Evolution

Volume 27, issue 10, pages 2312-2321
Published in print October 2010 | ISSN: 0737-4038
Published online May 2010 | e-ISSN: 1537-1719 | DOI: https://dx.doi.org/10.1093/molbev/msq117
Can a Sex-Biased Human Demography Account for the Reduced Effective Population Size of Chromosome X in Non-Africans?

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Sex-biased demographic events can result in asymmetries in female and male effective population size that can lead to different patterns of genetic variation on chromosome X than are expected based on the patterns on the autosomes. Previous studies point to a period around the time of the dispersal of anatomically modern humans out of Africa when chromosome X experienced a significant reduction in effective population size relative to the autosomes. Here, we explore whether a sex-biased demographic history could explain these observations. We use coalescent simulations to show that a model of primarily male migration during the out-of-Africa dispersal can produce the striking patterns that are observed when comparing patterns of genetic variation on the autosomes and chromosome X. The model involves a history in which after the founder population of non-Africans lost much of its genetic diversity, subsequent mostly male gene flow from an African source brought new diversity into the population. We also explore two additional models, one of sex-biased generation time and one of a substructured population during the dispersal out of Africa with primarily female migration among demes. These latter models cannot account for the magnitude of the observed reduction in chromosome X effective population size, although it is plausible that they played a more minor role in producing the striking chromosome X/autosome patterns.

Keywords: gender-biased demography; chromosome X; autosomes; effective population size; coalescent simulations; human

Journal Article.  7571 words.  Illustrated.

Subjects: Evolutionary Biology ; Molecular and Cell Biology

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