for National Geographic News
Signs of recent evolution by natural selection are widespread across the human genome, experts say.
Genome researchers at the University of Chicago have identified more than 700 regions in human DNA where apparently strong selection has occurred, driving the spread of genes linked to a broad range of characteristics.
"These are very recent eventswithin the past ten thousand years," said Jonathan Pritchard, a geneticist whose laboratory team conducted the study.
The results suggest that humans in different regions have continued to adapt in numerous ways to both environmental changes and cultural innovations.
Many of the genetic changes Pritchard's group detected came during or after the emergence of agriculture, beginning about 10,000 years ago, and long after the formation of modern human populations.
Some of the genes most strongly affected by selection were those associated with skin color, bone structure, and the metabolism of different foods.
Using newly available data, the scientists conducted a genome-wide scan for genetic variants showing evidence of recent selection in European, Asian, and African populations.
Most of the selected genes varied strongly among the three groups, suggesting that humans were adapting to pressures specific to different parts of the world.
The results are published in this month's issue of the journal PLoS Biology.
Changing World, Changing Genes
Positive selection occurs when a specific gene gives its carriers some advantage over others who lack the gene.
The methods used by Pritchard's group detected apparently beneficial genes that have spread through a large portion of the population but are not yet universal.
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