We evolved to eat berries rather than bagels, to live in mud huts rather than condos, to sprint barefoot rather than play football - or did we? Are our bodies and brains truly at odds with modern life? Everyone is fond of paleofantasies, stories about how humans lived eons ago, and we use them to explain why many elements of our lives, from the food we eat to the way we raise our children, seem very distant from what nature intended. We sometimes assume that humans in a modern society aren't evolving any more, that we have somehow freed ourselves from evolution, or at the very least, that evolution always requires so long to act that we can't expect to have adapted to our current circumstances. But popular theories about how our ancestors lived - and why we should emulate them - are often based on speculation, not scientific evidence, and they reflect a basic misunderstanding about how evolution works.