Human evolutionary genetics is too sexy…

By Razib Khan | December 23, 2008 12:04 am

Say you have a abstruse paper such as, Accelerated genetic drift on chromosome X during the human dispersal out of Africa:

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.

Over at Gene Expression Classic p-ter expresses his befuddlement:

At the same time, another group (Keinan et al.) was independently looking at this issue in other datasets. Their analysis, published today is markedly different. In particular, they see the exact opposite of the pattern in Hammer et al.–a decrease in the X/autosome ratio in effective population size compared to 0.75 (a figure from their paper is on the right. Note that the y-axis is the same in both this and the Hammer et al. figure–the x/autosome ratio in Ne. In both, the solid horizontal line is at 0.75). . And this is not due to extremely different methodologies–one of the analyses presented by Keinan et al. is very similar to that in Hammer et al., only using different data.
So this is all a bit odd, to say the least.

All right. So how does this play in the press? They go crazy! Did warfare drive out-of-Africa migration?:

Roving bands of men might have waged history’s first traceable war against the ancestors of all Europeans, Asians and other non-Africans, some 60,000 years ago.

  • Alan Kellogg

    The journey was hard, and the women with the various groups died in larger numbers than the men did. That’s my conjecture.

  • Fly

    A person centric model of gene migration would suggest small traveling bands with only a few women surviving.
    A gene centric model gives a different picture. Consider humanity as being spread continuously along a migration path. Genes are transported along that path as men and women move between between tribes. The female gene carriers remain close to home while the male carriers range much farther. The effective population size for the male carried genes would be greater than the effective population of the female carried genes.

  • plschwartz

    When I was a kid learning Bible stories, I wondered where all the other people came from. First there are only A&E then suddenly there was Cain being exiled into the land of Nod. Where did the Nodians come from.
    So with this story. Our ancestors, mostly men came out of Africa. So who were the Nodians that they made tender sweet love with? Were they mating ladies of less advanced groups? wouldn’t they then have produced hybrids? Where are the genes of these lesser ladies. Etc??


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

Gene Expression

This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at


See More


RSS Razib’s Pinboard

Edifying books

Collapse bottom bar