About 30,000 years ago, a tiny mutation arose in a gene now known as EDAR and began to spread rapidly in central China, eventually becoming common in the region.
This week, scientists at Harvard University offered some explanations for why the EDAR mutation may have been so successful. They observed how the gene affects mice, animals long used in disease research but never before for the study of human evolution.
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.
The research showed how scientists are getting better at identifying the DNA changes that made humans what they are today. The analysis also revealed that mutations in genes involved in bone density, skin color and immune system function were probably important in helping humans adapt to new environments as they spread around the world.
“You can let the genome tell you what’s been important in human evolution," said Harvard University geneticist Pardis Sabeti, senior author of the two studies published in Cell.
Living beings evolve through a process known as selection. Organisms with advantageous traits thrive, passing their DNA to another generation. Harmful traits die off when their hosts can’t live long enough to reproduce.
Scientists can recognize patterns in DNA that indicate a particular version of a gene has spread through a population because it boosts survival. But those beneficial mutations are usually passed down along with thousands of other variants that happen to live in their chromosomal neighborhood.
That has made it hard for researchers to determine exactly which mutations tweaks conferred the competitive advantage.
Sabeti and an international group of scientists are using multiple techniques to dig out the key drivers of human evolution in the avalanche of genetic data made possible by faster, cheaper sequencing technology.