More on worlwide and genomewide variation...
Just to finish the trilogy -- the three papers examining genome wide polymorphism in this weeks Nature and Science -- I should mention Li et al.'s Science paper covering essentially the same as the Jakobsson et al. I just reviewed.
Worldwide Human Relationships Inferred from Genome-Wide Patterns of Variation
Li et al.
Abstract
Human genetic diversity is shaped by both demographic and biological factors and has fundamental implications for understanding the genetic basis of diseases. We studied 938 unrelated individuals from 51 populations of the Human Genome Diversity Panel at 650,000 common single-nucleotide polymorphism loci. Individual ancestry and population substructure were detectable with very high resolution. The relationship between haplotype heterozygosity and geography was consistent with the hypothesis of a serial founder effect with a single origin in sub-Saharan Africa. In addition, we observed a pattern of ancestral allele frequency distributions that reflects variation in population dynamics among geographic regions. This data set allows the most comprehensive characterization to date of human genetic variation.
The results do not differ that much from Jakobsson et al. but the analysis is different.
First, they use a maximum likelihood method to cluster the sampled individuals into K unknown "ancestral clusters" and considered the clustering obtained with different Ks. For increasing Ks, the individuals cluster into smaller and smaller groupings, indicating their relatedness compared to the whole sample.
Once K is high enough (K=7), the populations mainly cluster together, with most populations being derived from the same single cluster but with some populations (Middle Easterns and South/Central Asians) being a mix of the ancestral clusters.
They then construct a maximum likelihood phylogeny for the populations and find that it fits nicely with the Out of Africa model.
Considering haplotype heterozygosity, they observe that heterozygosity decreases with distance from East Africa, similar to what Jakobsson et al. reports.
Li, J.Z., Absher, D.M., Tang, H., Southwick, A.M., Casto, A.M., Ramachandran, S., Cann, H.M., Barsh, G.S., Feldman, M., Cavalli-Sforza, L.L., Myers, R.M. (2008). Worldwide Human Relationships Inferred from Genome-Wide Patterns of Variation. Science, 319(5866), 1100-1104. DOI: 10.1126/science.1153717