Wednesday, August 01, 2007

Really recent human evolution   posted by Razib @ 8/01/2007 02:26:00 PM

Recent Genetic Selection in the Ancestral Admixture of Puerto Ricans:
Recent studies have used dense markers to examine the human genome in ancestrally homogeneous populations for hallmarks of selection. No genomewide studies have focused on recently admixed groups-populations that have experienced admixing among continentally divided ancestral populations within the past 200-500 years. New World admixed populations are unique in that they represent the sudden confluence of geographically diverged genomes with novel environmental challenges. Here, we present a novel approach for studying selection by examining the genomewide distribution of ancestry in the genetically admixed Puerto Ricans. We find strong statistical evidence of recent selection in three chromosomal regions, including the human leukocyte antigen region on chromosome 6p, chromosome 8q, and chromosome 11q. Two of these regions harbor genes for olfactory receptors. Interestingly, all three regions exhibit deficiencies in the European-ancestry proportion.

The settlement of the New World in the Iberian colonies is characterized by two broad dynamics. First, the mass die offs of many populations due to the introduction of Eurasian pathogens. Second, the hybridization of indigenous female lineages with European male ones (and later African ones). Until recently it was assumed that the Puerto Rican population was dihybrid, that is, Africans and Europeans. But new data suggests a substantial indigenous maternal contribution.