About 30,000 years ago, a tiny mutation arose in a gene known as EDAR and began to spread rapidly in central China, eventually becoming common in the region.
The small change, substituting one chemical letter of DNA for another, may have helped humans in Asia survive crippling heat and humidity by endowing them with extra sweat glands, the scientists reported Thursday in the journal Cell. It may also have made people with the mutation more attractive to the opposite sex by allowing them to grow thicker hair or fuller breasts.
People who inherited the variant may have reproduced more successfully because having more sweat glands helped their bodies cool off in hot, humid weather.
Or it might have spread through sexual selection. Thicker hair may have been more appealing in a mate. In addition, the mutation could have changed breast size or shape, making people who had it more attractive to the opposite sex.
That scientists could study a mouse and reveal such insights into human evolution was “amazing,” said Green, who co-wrote an essay about the work that was also published in Cell on Thursday.
The story was similar for the TLR-5 gene, which is involved in protecting the body from certain bacteria. Instead of testing in mice, the scientists used cell cultures in lab dishes to demonstrate that the mutation reduced the immune system’s inflammatory response to a key protein in the bacterial pathogens.
The team’s analysis suggested that many of the key genetic changes weren’t in genes themselves, but in regions of the chromosome that scientists think contain instructions for how those genes should be turned on and off, or tuned up or down, Sabeti said.