What Killed the World’s Most Famous Fossil?

In 1974, scientists working in Ethiopia uncovered an extraordinary female skeleton, whom they called Lucy. She was 3.2 million years old, and belonged to a new species of hominid now known as Australopithecus afarensis. Her brain was small and chimp-sized, but her hips and legs that were clearly built for upright walking—a unique blend of features which revealed that our ancestors evolved a two-legged gait before their brains became big. Lucy has since become a household name, and it’s easy to forget that she was more than just an avatar of human evolution. She was also a person. Back when her now-famous skeleton was still wrapped by flesh and skin, she was walking around Africa. She ate,...