A Hair of the Lizard that Spawned You

Us hairy, big-brained bipeds like to lord it over our scaly, slimy, feathered fellow creatures (either living or extinct), which is why it's bracing to hear that scientists have traced the origin of hair back to the last common ancestor of reptiles, birds and mammals. Based on an analysis of the keratin-like proteins in the claws of contemporary chickens and green anole lizards, it seems that the likely ancestor of the Hair Club for Mammals lived about 310 million years ago, and probably looked more like a large salamander than a prehistoric version of Cousin Itt.

So why did mammals go on to sprout hair, while lizards and birds kept their scales and feathers? Well, evolution works in not-so-mysterious ways--clearly, the genes that express keratin mutated in the direction of producing hair where it was environmentally favorable to do so, and scales and feathers where a thick, furry, full-body toupee would have been a bit over the top.