I've heard this before, but it's fascinating every time it comes up.
There is such a push in society to drink milk for calcium for strong bones. But really, it's not natural for us to be drinking milk past infancy. It's the perfect example of a market being created out of nothing. Of misinformation that is repeated so often it becomes fact. If you really think about it, how many prehistoric people were grabbing pregnant cows to suckle on?
Lactose intolerant people are actually the normal ones.