Could primates have evolved into humans without knowing how to cook? For 10 years, Harvard University primatologist Richard Wrangham has gathered data that he says show that the discovery of cooking allowed humans to evolve. The only snag, according to Scientific American: He has yet to prove that humans' ancestors could control fire, a missing link that some scientists say casts doubt on the cooking hypothesis.

Chimpanzees' diets of raw, bitter fruits couldn't provide enough energy to support humans' relatively large brains,...