More Than 700 Genetic Variants Found That May Be Targets Of Recent Natural Selec

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More Than 700 Genetic Variants Found That May Be Targets Of Recent

Natural Selection During The Past 10,000 Years Of Human Evolution

http://www.medicalnewstoday.com/medicalnews.php?newsid=39000

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.

In one of the first comprehensive genome scans for selection, the

researchers found widespread evidence of evolution in all of the

populations studied. Their results are published and freely available

online in the open-access journal PLoS Biology.

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.

" This approach allows us to take a broad prospective to see what

kinds of biological systems are undergoing adaptation, " said

Pritchard, professor of human genetics and corresponding author of

the paper. " There have been a lot of recent changes--the advent of

agriculture, shifts in diet, new habitats, climatic conditions--over

the past 10,000 years, and we're using these data to look for those

signals of very recent adaptation. "

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.

" Presumably, " Pritchard said, " a few thousand years from now, if

selection pressure remains the same, everyone will have [the selected

mutation]. "

Classifying all the genes by their biological functions, the

researchers listed the top 16 categories that had the strongest

signals, including olfaction (the sense of smell), reproduction-

related processes and carbohydrate metabolism, which includes the

lactase gene.

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. " Only one of these five signals was known before, "

Pritchard said. The authors also found signals of reproductive

selection and sexual competition in all three populations.

" Many of the signals, however, seem to be more specific to modern

human adaptation, " he said, " like skin pigmentation, which may

respond to changes in habitat, or metabolism genes, like lactase,

which may respond to changes in agriculture. "

The study was funded by the National Institutes of Health.

Citation: Voight BF, Kudaravalli S, Wen X, Pritchard JK (2006) A map

of recent positive selection in the human genome. PLoS Biol 4(3):

e72.