Feathers are like eyes or or hands. They’re so complex, so impressive in their adaptations, so good at getting a job done, that it can be hard at first to believe they evolved. Feathers today are only found on birds, which use them to do things like fly, control their body temperature, and show off for potential mates. The closest living relatives of birds–alligators and crocodiles–are not exactly known for their plumage. At least among living things, the glory of feathers is an all-or-nothing affair.

But the more we get to know feathers, the more we can appreciate how they evolved. The general rule is that complex things–be they feathers, hands, or eyes–take a very long time to evolve. As I