Parasites drove human genetic variation: Adapting to pathogens was more important than climate and diet in driving natural selection.

Link: Parasites drove human genetic variation: Adapting to pathogens was more important than climate and diet in driving natural selection.

Modern humans began to spread out from Africa approximately 100,000 years ago. They settled in distant lands, where they had to adapt to unfamiliar climates, find different ways to feed themselves and fight off new pathogens. A study now suggests that it was the pathogens, particularly parasitic worms, that had the biggest role in driving natural selection — but that genetic adaptation to them may also have made humans more susceptible to autoimmune diseases.