In a study analyzing the genomes of 210,000 people in the United States and Britain, researchers have found that the genetic variants linked to Alzheimer’s disease and heavy smoking are less frequent in people with longer lifespans, suggesting that natural selection is weeding out these unfavorable variants in both populations. “It’s a subtle signal, but we find genetic evidence that natural selection is happening in modern human populations,” said study coauthor Joseph Pickrell, an evolutionary geneticist at Columbia and New York Genome Center.
The study may be the first to take a direct look at how the human genome is evolving in a period as short as one or two generations. As more people agree to have their genomes sequenced and studied, researchers hope that information about how long they lived, and the number of kids and grandkids they had, can reveal further clues about how the human species is currently evolving.