As reported by Scientific American, Researchers have concluded that only 10,000 years ago, the human transition from living off the land to actively raising crops and domesticated animals was accompanied by an accelerated rate of evolutionary change. The pressure for this change occcurred because populations became highly concentrated compared to hunter/gatherer societies.  This concentration raised many new biological challenges, such as staving off serious diseases that were common in crowded living spaces. How much did human biological changes accelerate?

Comparing the amount of genetic differentiation between humans and our closest relatives, chimpanzees, suggests that the pace of change has accelerated to 10 to 100 times the average long-term rate, the researchers write in Proceedings of the National Academy of Sciences USA.

What kind of biological changes occurred in our species in these recent times?  One quite visible recent change was skin color, but there were many other recent changes:

“Their bodies and teeth shrank. Their brains shrank, too,” he adds. “But they started to get new alleles [alternative gene forms] that helped them digest the food more efficiently. New protective alleles allowed a fraction of people to survive the dread illnesses better.”

By looking for wide swaths of genetic material that vary little from individual to individual within these sections of great variation, the researchers identified regions that both originated recently and conferred some kind of advantage (because they became common rapidly). For example, the gene known as LCT gave adults the ability to digest milk and G6PD offered some protection against the malaria caused by Plasmodium falciparum parasite.

“Ten thousand years ago, no one on planet Earth had blue eyes,” Hawks notes, because that gene—OCA2—had not yet developed. “We are different from people who lived only 400 generations ago in ways that are very obvious; that you can see with your eyes.”

According to the researchers, not all human populations changed equally.

For example, Africans show a slightly lower mutation rate. “Africans haven’t had to adapt to a fundamentally new climate,” because modern humanity evolved where they live, [anthropologist Gregory] Cochran says. “Europeans and East Asians, living in environments very different from those of their African ancestors and early adopters of agriculture, were more maladapted, less fitted to their environments.”