An interesting fact in Cochran and Hapending's 10,000 Year Explosion, is that raising cattle for milk, as opposed to meat, generates 5 times the calories for a set amount of land. Thus, the milk raising people were able to outbreed, and eventually overwhelm, those whose cultures did not raise cattle for milk. The interesting point is that this is a strange form of genocide, because a lactose intolerant group could not simply adopt dairy farming, because without the lactose tolerant gene, it would be useless (and uncomfortable). Eventually, groups battle, and the numbers of the lactose tolerant simply overwhelms the lactose intolerant. Culture and genes are linked, because with the lactose tolerant genes you can't have a dairy culture, and without a dairy culture, you can't select for lactose tolerance.
I love a tall glass of milk, any time of the day. I still remember that on steak day my most mostly Jewish frat brothers would look in disgust as I drank milk with my steak. It wasn't the Talmudic restrictions that bothered them, rather, they found the combination repulsive, like eating chocolate covered potato chips.