Accelerated genetic drift on chromosome X during the human dispersal out of Africa

Nat Genet. 2009 Jan;41(1):66-70. doi: 10.1038/ng.303. Epub 2008 Dec 21.


Comparisons of chromosome X and the autosomes can illuminate differences in the histories of males and females as well as shed light on the forces of natural selection. We compared the patterns of variation in these parts of the genome using two datasets that we assembled for this study that are both genomic in scale. Three independent analyses show that around the time of the dispersal of modern humans out of Africa, chromosome X experienced much more genetic drift than is expected from the pattern on the autosomes. This is not predicted by known episodes of demographic history, and we found no similar patterns associated with the dispersals into East Asia and Europe. We conclude that a sex-biased process that reduced the female effective population size, or an episode of natural selection unusually affecting chromosome X, was associated with the founding of non-African populations.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Africa
  • Chromosomes, Human, X / genetics*
  • Emigration and Immigration*
  • Evolution, Molecular
  • Female
  • Genetic Drift*
  • Genetic Variation
  • Humans
  • Male
  • Selection, Genetic
  • Sex Characteristics
  • Sex Ratio