The dawn of dairy farming in Europe occurred thousands of years before most people evolved the ability to drink milk as adults without becoming ill. Now researchers think they know why: lactose tolerance was beneficial enough to influence evolution only during occasional episodes of famine and disease, explaining why it took thousands of years for the trait to become widespread1.
The theory — backed up by an analysis of thousands of pottery shards and hundreds of ancient human genomes as well as sophisticated modelling — explains how the ability to digest milk became so common in modern Europeans, despite being almost non-existent in early dairy farmers. This ability, known as lactase persistence, comes from an enzyme that breaks down milk sugar and usually shuts down after young children are weaned.
The study, published in Nature on 27 July, is the first major effort to quantify the forces that have shaped this trait, says Shevan Wilkin, a molecular archaeologist at the University of Zurich, Switzerland. “Lactase-persistence evolution was much more complicated than we ever thought.”
— source scientificamerican.com | Ewen Callaway | Jul 28, 2022