The gene that is responsible for making the enzym that allows us to digest cowmilk is very much of a newcomer. It also developed only locally. If you look at the Asian population, most people have a "cowmilk allergy". This allergy is in fact the natural state for our ancestors.
And indeed, which mammal except for man drinks milk after it's infancy? None AFAIK. Milk is, among other things, bad for the slimeproduction, heavy to digest and indeed bad for bones (even more so as you age). The goverment fairytale of milk being very good came into existence only because of HUGE overproduction. In holland we called it "de melkplas en de boterberg" (The milk-lake and the buttermountain). One other reason, in Europe at least, to promote drinking milk, was the period after the second world war. People were underfed and milk is quite rich in energy. Which is a fact but that does not make milk healthy. Since I studied biology at university, I never drink milk anymore -and hey, still haven't broken any bones-. I think it is not so bad for children to drink milk now and then to get some extra proteins and energy but I think every day can't be good. Some recent research is also linking excessive use of milk to colon-cancer but I haven't checked on the results for a while.
In short: I advise, as a biologist, against drinking milk often.