A comparison of brain tissue from monkeys, chimps and humans suggests that our brains produce the chemical messenger dopamine, which plays a major role in pleasure and rewards, far differently.
Long before cooking was common, early humans needed extra energy to fuel bigger bodies and brains. Scientists say simple stone cutting tools likely allowed small-toothed meat eaters to thrive.
Humans have lighter bones than other primates, and that change happened a lot later than anthropologists had thought. Blame our sedentary ways after our ancestors took up farming.