That’s the theory being offered by Harvard’s Richard Wrangham.

And with Homo sapiens, what makes the species unique in Dr Wrangham’s opinion is that its food is so often cooked.

Cooking is a human universal. No society is without it. No one other than a few faddists tries to survive on raw food alone. And the consumption of a cooked meal in the evening, usually in the company of family and friends, is normal in every known society. Moreover, without cooking, the human brain (which consumes 20-25% of the body’s energy) could not keep running. Dr Wrangham thus believes that cooking and humanity are coeval.

(via The Meaningfulness of Little Things)