If you could escape the human time scale for a moment, and regard evolution from the perspective of deep time, in which the last 10,000 years are a short chapter in a long story, you'd say: Things are pretty wild right now.
In the most massive study of genetic variation yet, researchers estimated the age of more than one million variants, or changes to our DNA code, found across human populations. The vast majority proved to be quite young. The chronologies tell a story of evolutionary dynamics in recent human history, a period characterized by both narrow reproductive bottlenecks and sudden, enormous population growth.
The evolutionary dynamics of these features resulted in a flood of new genetic variation, accumulating so fast that natural selection hasn’t caught up yet. As a species, we are freshly bursting with the raw material of evolution.
“We’ve gone from several hundred million people to seven billion in a blink of evolutionary time,” said Akey. “That’s had a profound effect on structuring the variation present in our species.”
The researchers sequenced in exhaustive detail protein-coding genes from 6,515 people, compiling a list of every DNA variation they found — 1,146,401 in all, of which 73 percent were rare.
Akey’s group found that rare variations tended to be relatively new, with some 73 percent of all genetic variation arising in just the last 5,000 years. Of variations that seem likely to cause harm, a full 91 percent emerged in this time.
“Humans today carry a much larger load of deleterious variants than our species carried just prior to its massive expansion just a couple hundred generations ago,”
The inverse is also true.
Indeed, the genetic seeds of exceptional traits, such as endurance or strength or innate intelligence, may now be circulating in humanity. “The genetic potential of our population is vastly different than what it was 10,000 years ago,” Akey said.