Famine and disease drove the evolution of lactose tolerance in Europe

Milk - Source: Myriams-Fotos on Pixabay Prehistoric people in Europe were consuming milk thousands of years before humans evolved the genetic trait allowing us to digest the milk sugar lactose as adults, finds a new study led by UCL and University of Bristol researchers. The research, published in Nature , mapped pre-historic patterns of milk use over the last 9,000 years, offering new insights into milk consumption and the evolution of lactose tolerance. Until now, it was widely assumed that lactose tolerance emerged because it allowed people to consume more milk and dairy products. But this new research shows that famine and exposure to infectious disease best explain the evolution of our ability to consume milk and other non-fermented dairy products. Joint senior author Professor Mark Thomas (UCL Genetics, Evolution & Environment) said: "In late prehistory, as our ancestors started living in larger settlements, their health was increasingly impacted by poor sanitation and increased pathogen loads. Under such conditions, even more so during times of famine, consuming milk would have increased death rates, particularly among those unable to digest the lactose in milk. Those who were able to digest lactose were thus more likely to pass on their genes enabling them to safely drink milk." While most European adults today can drink milk without discomfort, two thirds of adults in the world today, and almost all adults 5,000 years ago, can face problems if they drink too much milk.