That's circular reasoning. The only reason it was "only present in the infant diet" is because of the evolution of lactose intolerance. Without that development

That's circular reasoning. The only reason it was "only present in the infant diet" is because of the evolution of lactose intolerance. Without that development, children would keep drinking milk for as long as they could get away with it. But don't take my word for it; here's what Slate has to say: "With Cain weaned, Abel could claim more of his mother's attention and all of her milk. This kept a lid on sibling rivalry [...] while allowing women to bear more young." http://www.slate.com/articles/health_and_science/human_evolution/2012/10/evolution_of_lactose_tolerance_why_do_humans_keep_drinking_milk.html http://www.slate.com/articles/health_and_science/human_evolu...