Other anthropologists think it’s because meat-eating isn’t the key at all, that the real key is cooked tubers, like yams. They say an increase in calories is what’s important when it comes to the development of larger brains, and that cooked tubers would have provided just such a boost. And root vegetables are believed to have been plentiful in the environment where humans evolved. Cooking would have made tubers easier to digest, and therefore richer in calories. Cooking is the target of major criticism though. Most archaeologists believe humans didn’t begin cooking until about 250,000 years ago.