Apparently, modern chimps can eat meat, but they need to spend so much time chewing it that the caloric benefit is small. Cooking the food is far more efficient.
H. habilis may not have cooked food, but spent time pounding it and making it easier to digest. This allowed them to digest it better. Pounding tools are common in H. habilis sites.
To support this view, he says that humans have small teeth, a small mouth and a short digestive tract made possible by eating primarily cooked food. He further claims that cooked food allows greater absorption of calories and therefore allowed people to support their giant brain.
There is an interesting interview on NPR's site. Here he talks about the well-known evolutionary adaptation of cattle raising peoples to metabolise lactose in adulthood.
He pointed out that acrylamide, which is found in cooked foods including french fries, causes cancer in rats, but has not been shown to cause cancer in people -- suggesting an (unproven) resistance in people to acrylamide-caused disease. This might show that people are evolutionarily adapted to eating cooked food. [Not everyone believes this.]
Today the Raw Food Movement, justifies itself as a return to pre-modern diets, but actually the human diet has been cooked for a while -- 1.8 million years actually.
Vegetarians should also contemplate how natural a vegetable-only diet is. One cannot argue that this is part of some utopian past. One can make the case that meat and milk are literally in our genes. In fairness, vegetarians can point to some positive health studies, and that it is possible in the modern agricultural age that the benefits of cooked foods are not as great as before.
