Recent Adaptation Evidence in the Human Genome

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Warning: Proud father’s posting ahead……

This past summer, one of the NY Times Tuesday Science issues was focused on evolution studies. One of the research papers highlighted by Nicholas Wade in his article titled, “Humans Have Spread Globally and Evolved Locally” , had native Kansan, Scott Williamson, as lead author. The work received quite a bit of additional publicity. Here’s the lead paragraphs of an article that I think is the best summary that I have seen written about the article.

Cornell Chronicle Online, July 11, 2007
Evidence that up to 10 percent of human genome may have changed very recently revealed by CU researchers
By Krishna Ramanujan

A Cornell study of genome sequences in African-Americans, European-Americans and Chinese suggests that natural selection has caused as much as 10 percent of the human genome to change in some populations in the last 15,000 to 100,000 years, when people began migrating from Africa.

The study, published in the June 1 issue of PLoS (Public Library of Science) Genetics, looked for areas where most members of a population showed the same genetic changes. For example, the researchers found evidence of recent selection on skin pigmentation genes, providing the genetic data to support theories proposed by anthropologists for decades that as anatomically modern humans migrated out of Africa and experienced different climates and sunlight levels, their skin colors adapted to the new environments.

However, the study found no evidence of differences in genes that control brain development among the various geographical groups, as some researchers have proposed in the past.

Now I’m not just bringing this to your attention because Scott happens to be our (Carol’s and my) son. Actually, I think you’ll find the results timely for your classroom–particularly the table that summarizes the different recent adaptations in various populations. In addition, you might notice that that they provide contrary evidence to some of the claimed brain development adaptations recently reported. Science at work. Check it out, you’ll find the table useful.

Here’s the author’s summary from the article:

Author Summary

A selective sweep is a single realization of adaptive evolution at the molecular level. When a selective sweep occurs, it leaves a characteristic signal in patterns of variation in genomic regions linked to the selected site; therefore, recently released population genomic datasets can be used to search for instances of molecular adaptation. Here, we present a comprehensive scan for complete selective sweeps in the human genome. Our analysis is complementary to several recent analyses that focused on partial selective sweeps, in which the adaptive mutation still segregates at intermediate frequency in the population. Consequently, our analysis identifies many genomic regions that were not previously known to have experienced natural selection, including consistent evidence of selection in centromeric regions, which is possibly the result of meiotic drive. Genes within selected regions include pigmentation candidate genes, genes of the dystrophin protein complex, and olfactory receptors. Extensive testing demonstrates that the method we use to detect selective sweeps is strikingly robust to both alternative demographic scenarios and recombination rate variation. Furthermore, the method we use provides precise estimates of the genomic position of the selected site, which greatly facilitates the fine-scale mapping of functionally significant variation in human populations.