Human genome reveals evidence of recently evolving genes

By scanning the entire human genome in search of genetic variations that may signal recent evolution, University of Chicago researchers found more than 700 genetic variants that may be targets of recent natural positive selection during the past 10,000 years of human evolution.

Published online March 7, 2006, in the Public Library of Science-Biology in a paper, titled "A Map of Recent Positive Selection in the Human Genome," the researchers found widespread evidence of evolution in all of the populations studied.

The data analyzed here were collected by the International HapMap Project and consist of genetic data from 209 unrelated individuals who are grouped into three distinct populations: 89 East Asians, 60 Europeans, and 60 Yorubans from Nigeria. The researchers found roughly the same number of signals of positive selection within each population. They also found that each population shares about one fifth of the signals with one or both of the other groups.

Among the more than 700 signals the team found were previously known sites of recent adaptation, such as the salt-sensitive hypertension gene and the lactase gene--the strongest signal in the genome hunt. The lactase mutation, which enables the digestion of milk to continue into adulthood, appeared in approximately 90 percent of Europeans.

The team used the PANTHER (Protein ANalysis THrough Evolutionary Relationships) Classification System to classify all the genes in the genome by their biological functions into 222 categories.

Other processes that show signals of selection include genes related to metabolism of foreign compounds, brain development and morphology. For example, the researchers found five genes involved in skin pigmentation that show evidence of positive selection in Europeans.

Among East Asians, the researchers found a strong signal of selection in the alcohol dehydrogenase (ADH) cluster, the enzymes that break down alcohol. It's widely known that many East Asians have a mutation in a related gene that renders this pathway nonfunctional.

"That's why a lot of East Asians can't metabolize alcohol," Pritchard said, "but mutations in this pathway must have some additional positive effect that has been favored by natural selection."

University of Chicago Hospitals: Scan of human genome reveals evidence of more than 700 recently evolving genes

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