In the most massive study of genetic variation yet, researchers have determined that the age of more than one million variants ~ or changes to our DNA code ~ found across human populations is quite young.
The chronologies tell a story of evolutionary dynamics in recent human history ~ the last 10,000 years ~ a period characterized by both narrow reproductive bottlenecks and enormous population growth.
According to Wired.com:
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.
“Most of the mutations that we found arose in the last 200 generations or so. There hasn’t been much time for random change or deterministic change through natural selection,” said geneticist Joshua Akey of the University of Washington. “We have a repository of all this new variation for humanity to use as a substrate. In a way, we’re more evolvable now than at any time in our history.”
But these findings can also been seen from another angle. They teach us about human evolution, in particular the course it’s taken since modern Homo sapiens migrated out of Africa.
“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.”
For practical reasons, rare genetic variants have only been studied for the last several years because it’s been too expensive. Genomics focused mostly on what are known as common variants.