When did humans start cooking food, and how did it change us?

The answer

Evidence suggests humans began controlling fire and cooking food around 1.8 million years ago. Cooking essentially pre-digests food externally, allowing our ancestors to absorb far more calories with less digestive effort. This surplus energy fueled the rapid expansion of the human brain - which consumes 20% of our energy despite being only 2% of body mass - making cooking arguably the most transformative technology in human evolution.