Why do humans have such big brains compared to other primates? Anthropologists generally agree that this trend in evolution was spurred by diet. If any of us ate like wild chimpanzees or gorillas we wouldn't do very well. We lack the colonic power to process fiber into large amounts of short-chain fatty acids and chimp diets just aren't calorically rich enough for our brains. Anthropologists are divided on which foods enabled our large brain size, but there are two popular theories:
Richard Wrangham is the main proponent of the first theory and has written a pop-sci book about it called Catching Fire.
Notice what wasn't on that list: fruit. There is little evidence that it was important in our more recent evolution or that it was an important part of our "natural diet."
Meat can be eaten raw, but you can't get much out of raw tubers. So the advent of widespread fire use is important in these arguments. Wrangham argues that humans have been using fire regularly for a very long time, but other researchers aren't so sure. A recent study found evidence that hominids in Northern Europe may not have used fire habitually:
"The European evidence strongly suggests that the habitual and controlled use of fire was a late phenomenon," Villa and Roebroeks conclude.
The findings controversially suggest that people migrated from Africa to the below-freezing winter temperatures of Europe without fire. These early hominins might have combined a high-protein diet with a highly active lifestyle to survive, the researchers speculate.
The conclusion also questions Wrangham's hypothesis that an increase in human brain size was tied to the invention of cooking.
Wrangham remains to be convinced. He points out that whenever cooking did arise, it would have led to profound biological effects on the humans alive at the time. There's no evidence for those effects in 400,000-year-old hominin fossils, he says.
I notice they conveniently avoid talking about these humans, as the sites they are talking about in Europe from 600,000 to 400,000 years ago are mostly Homo heidelbergensis, a type of human (or separate species depending on who you ask) quite physically different from modern humans. There is no evidence so far that this is one of our ancestors, though there is a theory that these folks evolved into Neanderthals and some of us have Neanderthal genes. The evidence for Homo sapiens doesn't appear in Europe until 35,000 years ago.
Either way the hominins in Europe 400,000 years ago had brains our size. And they seemed to have relied on meat or fish to power these brains. If they didn't have cooking they couldn't have relied on tubers for calories and long winters would have precluded fruit as a major calorie source.
John Hawks has a great post about this paper.
It can be hard to imagine the lives of these ancient humans living in the cold darkness without fires. However, some modern human cultures exist that forego cooking, including the people in Western Siberia. Perhaps their diet was similar. Clothing was probably an important item in such an environment.
I eat raw meat and fish when I can. I really enjoy it. I just started a paleo restaurant list on Dinevore and my top paleo restaurant is Takashi, which serves incredible raw liver. Seriously, I don't like liver that much, but damn this is good.