This totally ignores the reality that we've been undergoing natural selection in relation to those foods we've adopted over the last ten thousand years. Lactase persistence, for example, can be traced to 2 mutations, one found in highest concentration in Northern Europe, the other in West Africa (if I remember correctly). That 13% of the human population with a mutation for lactase persistence have it because under conditions of dietary inclusion of dairy products, it has a selective advantage. In populations that don't eat dairy, there's no advantage to such a mutation so it would be unlikely to become widespread, and in populations that haven't had a mutation that results in lactase persistence enter their gene pool, it won't matter how much dairy they eat, they still won't have lactase as adults.
I'm Asian, so probably very unlikely to carry any genetic ability to continue to produce lactase into adulthood, yet I can drink milk (even pasteurized) quite comfortably. My dh (Jewish with roots in Northern and Eastern Europe) is um... noticeably lactose intolerant , yet even he isn't so uncomfortable that he will avoid dairy. And he tolerates yogurt and cheese without a problem at all. Of course, there are those who really can't drink milk, but I'm wondering if they are perhaps the exception rather than the rule.
So I guess the question that I have to answer for myself is whether dairy is more of a benefit than not.
The implication made by Marie, Metasequoia and others that dairy and grains, in and of themselves, are a root cause of the decline in health among neolithic people seems too far a stretch to me. Nevertheless, I would be really interested in seeing some arguments that are more about the direct links between milk and disease. (I'm not saying this in a snarky "prove it to me" kind of way; I really would like to understand this. Is it a protein-fat-carbohydrate ratio, as some have suggested? Some immunofactor that is good for cows, but maybe not humans?)
And although I have not yet read NPD :, I'm pretty fascinated by all the references people keep making to those fabulously healthy cheese-eating, milk-swigging Swiss. And the Masai. And the yogurt-eating, long-lived folks in western Asia. And all of Weston Price's results with high vitamin butter oil. Of course, other groups make it clear that one does not need to have milk in order to have a healthy, long life. But still, if milk is genetically inappropriate for humans, I'm having a hard time understanding these reports.