One thing that's missing from this is a more nuanced discussion of lactose intolerance. It's not a simple binary thing like celiac disease or an allergy. It's p

One thing that's missing from this is a more nuanced discussion of lactose intolerance. It's not a simple binary thing like celiac disease or an allergy. It's possible to consume around a cup (250ml) of milk per meal for lactose intolerant people, but doing so without experiencing typical lactose intolerance symptoms requires regular exposure and building up to those levels (possibly due to micro-biome effects). What that means is that a group of people that started introducing animal milk consumption with infants might also begin consuming milk through adulthood in small quantities. That would provide the sort of situation that would make it easy for adult lactose tolerance to have a major evolutionary advantage. If teens and adults are drinking small amounts of milk regularly as well as some amount of cheese then those who are lactose intolerant (the common case) will only be able to get calories from the fat and proteins. But anyone who has acquired lactose tolerance will be able to consume an unlimited amount of dairy products and will also gain around 40% more calories from the lactose. That's an enormous dietary boost especially for people who are struggling at the margins of livelihood and malnutrition. More calories means less stunted growth, which means stronger bodies, and a greater ability to survive through harsh winters or lean times.