The history of human evolution is written in the genome, and researchers have now pinpointed gene variants that may have helped humans to adapt to their environment.

Sharon Grossman and Pardis Sabeti of the Broad Institute in Cambridge, Massachusetts, and their colleagues used a computational tool to root out single-letter changes in the human genome that have been under selective pressure in the past 50,000 years. They found that one such variant seems to temper the immune response to certain types of bacteria, and may have been selected for when humans were exposed to high levels of infections.

In a separate paper, Sabeti and her co-workers introduced another of the gene variants that they uncovered into mice. The resulting animals had thicker hairs and a higher number of active sweat glands — traits borne by humans with the same variant. However, whether extra sweat glands benefited early humans is a matter of speculation.

Cell 152, 703–713; 691–702 (2013)