White skin & wheat?

A few days ago I put up a post, Why red Indians aren't white, where I offered up a rough & ready model for why the indigenous peoples of the New World are relatively swarthy at the same latitudes as Europe compared to Europeans. Regular readers of this weblog know that I have somewhat of an obsession with skin color genomics, and am puzzled by some issues, both empirical and theoretical, and have been attempting to generate plausible explanatory scenarios for what we know, and what we expect. But in the process I assume a lot, so I'm going to hit the primary background assumptions in this post, since I'll be posting the topic a fair amount for the near future. First, there's the theory and expectation. Vitamin D deficiency isn't good, not only does it cause rickets, but it suppresses the immune system. The standard model is that northern ...