Coop et al. 2009
Fri Jul 03 2009
The Role of Geography in Human Adaptation
Various observations argue for a role of adaptation in recent human evolution, including results from genome-wide studies
and analyses of selection signals at candidate genes. Here, we use genome-wide SNP data from the HapMap and CEPH-
Human Genome Diversity Panel samples to study the geographic distributions of putatively selected alleles at a range of
geographic scales. We find that the average allele frequency divergence is highly predictive of the most extreme FST values
across the whole genome. On a broad scale, the geographic distribution of putatively selected alleles almost invariably
conforms to population clusters identified using randomly chosen genetic markers. Given this structure, there are
surprisingly few fixed or nearly fixed differences between human populations. Among the nearly fixed differences that do
exist, nearly all are due to fixation events that occurred outside of Africa, and most appear in East Asia. These patterns
suggest that selection is often weak enough that neutral processes—especially population history, migration, and drift—
exert powerful influences over the fate and geographic distribution of selected alleles.
Various observations argue for a role of adaptation in recent human evolution, including results from genome-wide studies
and analyses of selection signals at candidate genes. Here, we use genome-wide SNP data from the HapMap and CEPH-
Human Genome Diversity Panel samples to study the geographic distributions of putatively selected alleles at a range of
geographic scales. We find that the average allele frequency divergence is highly predictive of the most extreme FST values
across the whole genome. On a broad scale, the geographic distribution of putatively selected alleles almost invariably
conforms to population clusters identified using randomly chosen genetic markers. Given this structure, there are
surprisingly few fixed or nearly fixed differences between human populations. Among the nearly fixed differences that do
exist, nearly all are due to fixation events that occurred outside of Africa, and most appear in East Asia. These patterns
suggest that selection is often weak enough that neutral processes—especially population history, migration, and drift—
exert powerful influences over the fate and geographic distribution of selected alleles.