Tuesday, October 18, 2005

Diffusion of HIV resistance   posted by Razib @ 10/18/2005 07:41:00 PM

The Geographic Spread of the CCR5 Δ32 HIV-Resistance Allele. A picture is worth a lot of words, so....

Note the appeal to the "wave of advance" model of R.A. Fisher, you've seen it before in reference to the possibility of advantageous alleles spreading throughout populations via selection without concomitant wholesale demographic dislocations and migrations. The authors of the above article, which is freely available to all via PLOS, suggest that one possible reason that the Δ32 mutation isn't more common is that selection hasn't had enough time to operate. For comparison, consider lactose tolerance, though in Eurasia the allele that confers the ability to adults to easily digest milk products as adults probably has its origins in Northern Europe, in places like Northern India the phenotype has reached ~70% levels of prevalence. Contrary to some Aryan fantasists this does not imply that an ancient influx of Swedes transformed the South Asian demographic landscape, rather, selection knows a good thing.