There’s an interesting glimpse into recent human evolution in the latest edition of PLoS Genetics. It comes from a team of scientists whose corresponding author is Chad Huff, of the University of Texas MD Anderson Cancer Center, Houston, Texas. The paper is titled “Evolutionary history of Tibetans inferred from whole-genome sequencing”. The team performed whole-genome sequencing of 27 Tibetan individuals and confirmed that present day Tibetans diverged from the ancestral Han Chinese population between 44 and 58 thousand years ago, but with significant admixture until some 9,000 years ago. They confirmed that one positively-selected haplotype EPAS1 arose in the common ancestors of Tibetans and Han through introgression from Denisovans. The haplotype has all but died out in present-day Han, but, because it confers advantages with altitude, has been strongly selected for in Tibetans. Another gene selected for was VDR, which is important in vitamin D metabolism. As they state in the paper: “In a study involving vitamin D status in a cohort of 63 Tibetans, the proportion of nomadic Tibetans with vitamin D deficiency was 100% with 80% of people having severe deficiency; the proportion of non-nomadic Tibetans with vitamin D deficiency ranges from 40% to 83%. Consistently, in another study, 61% of Tibetan children suffer from rickets and 51% have stunted growth. Such a high prevalence of vitamin D deficiency may be explained by the traditional Tibetan diet consisting of barley, yak meat and butter tea which are poor sources of vitamin D, and clothing habits in cold temperatures which allow for minimal skin exposure to the sunlight. Therefore, we hypothesize that VDR gene is positively selected to compensate for the lack of vitamin D”. Other gene variants selected for included the PTGIS gene which promotes vasodilation and angiogenesis, and KCTD12, which is concerned with hypoxia.

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