GENEALOGY-DNA-L Archives

From: steven perkins <>
Subject: [DNA] Article: Can a sex-biased human demography account for thereduced effective population size of chromosome X in non-Africans?
Date: Sun, 16 May 2010 21:24:23 -0400

MBE Advance Access published online on May 7, 2010
Molecular Biology and Evolution, doi:10.1093/molbev/msq117

© The Author 2010. Published by Oxford University Press on behalf of
the Society for Molecular Biology and Evolution. All rights reserved.
For permissions, please e-mail:


Research Article

Can a sex-biased human demography account for the reduced effective
population size of chromosome X in non-Africans?
Alon Keinan1,* and David Reich2,3

1 Department of Biological Statistics and Computational Biology,
Cornell University, Ithaca, NY
2 Department of Genetics, Harvard Medical School, Boston, MA
3 Broad Institute of Harvard and MIT, Cambridge, MA

* To whom correspondence should be addressed (Department of Biological
Statistics and Computational Biology, 102A Weill Hall, Cornell
University, Ithaca, NY 14853; Tel: 607-254-1328, Fax: 607-255-4698 ;
)

Received for publication October 2, 2009. Revision received April 9,
2010. Accepted for publication May 3, 2010.

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.

Key Words: gender-biased demography • chromosome X • autosomes •
effective population size • coalescent simulations • human
--

Steven C. Perkins
http://stevencperkins.com/
Online Journal of Genetics and Genealogy
http://jgg-online.blogspot.com/
Steven C. Perkins' Genealogy Page
http://stevencperkins.com/genealogy.html
Steven C. Perkins' Genealogy Blog
http://scpgen.blogspot.com/

This thread:

• [DNA] Article: Can a sex-biased human demography account for thereduced effective population size of chromosome X in non-Africans? by steven perkins <>

  • Re: [DNA] Article: Can a sex-biased human demography account forthe reduced effective population size of chromosome X innon-Africans? by David Faux <>