One theory for the incredibly rapid spread of lactose tolerance is that during times of famine, lactose intolerant people in Northern Europe would drink fresh m

One theory for the incredibly rapid spread of lactose tolerance is that during times of famine, lactose intolerant people in Northern Europe would drink fresh milk (out of desperation) and the resultant diarrhea would weaken them even more. https://www.npr.org/sections/thesalt/2012/12/27/168144785/an-evolutionary-whodunit-how-did-humans-develop-lactose-tolerance https://www.npr.org/sections/thesalt/2012/12/27/168144785/an...