Briana Pobiner in American Scientist:
Although the modern “paleodiet” movement often claims that our ancestors ate large amounts of meat, we still don’t know the proportion of meat in the diet of any early human species, nor how frequently meat was eaten. Modern hunter-gatherers have incredibly varied diets, some of which include fairly high amounts of meat, but many of which don’t. Still, we do know that meat-eating was one of the most pivotal changes in our ancestors’ diets and that it led to many of the physical, behavioral, and ecological changes that make us uniquely human.
…Cooking was unquestionably a revolution in our dietary history. Cooking makes food both physically and chemically easier to chew and digest, enabling the extraction of more energy from the same amount of food. It can also release more of some nutrients than the same foods eaten raw and can render poisonous plants palatable. Cooking would have inevitably decreased the amount of time necessary to forage for the same number of calories. In his 2009 book Catching Fire, primatologist Richard Wrangham postulates that cooking was what allowed our brains to get big. It turns out that using fossil skulls to measure brain size, we see the biggest increase in brain size in our evolutionary history right after we see the earliest evidence for cooking in the archaeological record, so he may be on to something.