Our genetic quirks

Two stories came out last week about two curious features in our body chemistry. On Wednesday,  the journal Nature explained the age old mystery: why do our fingers and toes wrinkle during a bath? So we can pick things up, of course!

Laboratory tests confirmed a theory that wrinkly fingers improve our grip on wet or submerged objects, working to channel away the water like the rain treads in car tyres.

On Thursday, the Atlantic.com ran this story about the iron we need - and that can poison us. Some of us carry a hereditary condition called hemochromatosis:

a genetic disease leading to a toxic accumulation of iron in his organs. A modern manifestation of an ancient DNA mutation, this disorder can be traced to a single unknown ancestor who lived millennia ago. This mutation allowed her (or him) to more readily absorb iron from food, which may have unexpectedly aided survival in lean times -- possibly at the expense of iron-overload in later generations. . . . [The mutation is found in] nearly one in ten individuals of northern European ancestry.

There are lots of mysteries: why did the mutation arise? Do you need two copies to develop the disease, or just one? Where did it arise and how did it spread? Why is is so common in people of Northern European descent? It's a great story - evolutionary medicine with a modern example.