Evolution persisted in agricultural era

Natural selection continued to sculpt humanity’s genetic identity after the Stone Age gave way to farming around 11,000 years ago, according to a new DNA analysis.

A team led by Jonathan K. Pritchard of the University of Chicago identified survival-enhancing gene variants that began spreading through human populations between roughly 10,800 and 6,600 years ago.

The scientists scanned the genomes of 89 East Asians, 60 Europeans, and 60 Africans to find DNA stretches recently affected by natural selection. Their technique exploits the tendency of DNA regions containing advantageous genes to spread quickly through populations and generate relatively few mutations.

More than 700 gene variants showed both those characteristics, Pritchard’s group reports in the March PLoS Biology. Scientists know the function of some of the genes whose variants were identified.

Some of the genes influence fertility and reproduction, such as one that affects the protein structure of sperm in East Asians and Africans. Four other highlighted genes contribute to skin pigmentation in Europeans; mutations in those genes have been linked to disorders that cause unusually light pigmentation or albinism.

Recent natural selection also affected various genes involved in skeletal development in each population, the team reports.

Additional genes spread through populations after the advent of agriculture as people adapted to new kinds of food and colonized new areas, the researchers say. These include genes that contribute to the processing of lactose in Europeans, alcohol in East Asians, and dietary fatty acids in all three populations studied.

Several genes that affect the brain also responded to natural selection during agricultural times, the investigators say. However, they found no such evidence for two brain genes previously touted as subjects of recent natural selection (SN: 9/24/05, p. 206: Available to subscribers at Genes tied to recent brain evolution).

Bruce Bower has written about the behavioral sciences for Science News since 1984. He writes about psychology, anthropology, archaeology and mental health issues.

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