I’ve often wondered why human head size isn’t more standardized. After all, we can be pretty sure that head size isn’t related to brain power, so what other reason would there be not to base natural selection on head size? Getting your head stuck in the neck of your sweater is a serious and life-threatening condition. Smaller heads use fewer resources and are more environmentally sustainable. Big heads need big hats. How many sheep does it take to make the wool in just one big-headed hat? I can imagine that three or four sheep devote themselves full-time to the making of just one hat. This is tricky because sheep are…