The Pith: Natural selection is a quick & dirty operator. When subject to novel environments it can react rapidly, bringing both the good and the bad. The key toward successful adaptation is not perfection, but being better than the alternatives. This may mean that many contemporary diseases are side effects of past evolutionary genetic compromises.
The above is a figure from a recent paper which just came out in Molecular Biology and Evolution, Crohn’s disease and genetic hitchhiking at IBD5. You probably have heard about Crohn’s disease before, there are hundreds of thousands of Americans afflicted with it. It’s an inflammatory bowel ailment, and it can be debilitating even to very young people. The prevalence also varies quite a bit by population. Why? It could be something in the environment (e.g., different diet) or genetic predisposition, or some combination. What the figure above purports to illustrate is the correlation between Crohn’s disease and the expansion of the agricultural lifestyle.
But don’t get overexcited Paleos! There are many moving parts to this story, and I need to back up to the beginning. The tens of thousands of …