OK, just one question: Why did our ancestors bother to domesticate milk cows, when they couldn't digest the milk in the first place? Did they know that some day, they would become lactose tolerant? If this is evolution, wouldn't that mean our ancestors had to be drinking milk, as adults, for a long time, in the hope that some day their children, or grandchildren, etc, would mutate that gene? Wow, our ancestors were VERY forward thinking.
1. Presumably they didn't originally domesticate cattle for milk, they domesticated them for meat.
2. As has already been noted, early humans could digest milk products, just not raw milk -- cheese and butter and fermented milk (tastes nasty but will keep you alive) were always edible.
No, our ancestors probably were mixed in who could or could not drink milk. Some could, some couldn't. Something happens, where other food sources are in bad shape. Just say plants other than grasses are killed off. The cow milk is a great source of fat. Those who were able to consume it, survive the drought and then reproduce. The classic study on this phenomena is the brittish rabbit and butterfly population. White was the dominant color, with some charcoalish too but in a vast minority. Once industrialization came, the air got really sooty. The whites got eaten off quickly by predators, now darker colors were more predominant. Then they stopped using so much coal, and it switched once again. If the recessive trait was totally killed off, the species might have died.
When someone asks a question like this, it becomes easy to see why a simplistic mythological tale of how the Gods created the world and man is easier to believe than a fairly uncomplicated theory. Who wouldn't want things to be easily explained?
To answer the question: They didn't domesticate damn milk cows, they domesticated cattle to slaughter and eat. This was easier than running them down when they were hungry. How hard do you think it would have been to see that those big old calves were drinking from udders just like our tiny little humans were drinking from boobs? Next thing you know, they are trying it out themselves, giving their children lower mortality rates. It really isn't that hard to figure out.
It's stupid stuff like this that makes people want to go and vote for Democrats anyway. No wonder they think Republicans are stupid and that they are enlightened. It's just the same as how Christians disdain the Greek and Norse mythologies who also seek to explain creation with their own silly stories.