Jon Udell's recent blog post turned me onto a very interesting talk by
Richard Wrangham, author of "Catching fire: how cooking made us human".
Wrangham talks about how cooking can greatly increase the capability for humans to be able to digest food. For example, eating a raw egg or a raw banana, you may only absorb about 50% of the nutrients. But cook that egg or banana and absorption can go up to 99%. For tests with meat done with pythons, cooked meat increased absorption by 12%, mashed meat increased absorption by 12%, and cooked and mashed meat by 23%.
I've heard of the expensive tissue hypothesis before (as has Wrangham obviously), where the theory is that by eating meat humans were able to shorten their digestive tracts and have more energy available to increase their brain sizes. But while meat is more nutrient dense than plants, the fact that you can absorb 20-50% more nutrients from cooked/processed food over raw food could well have been the main driving factor in the increase in the humans brain size.
He also makes the point that this would greatly influence culture, as humans would have more time for other things. You'd think that cooked food wouldn't save too much time on the eating side, but Wrangham makes the point that a chimpanzee will spend 6 hours a day chewing. That's a lot of chewing!
This would also explains why it's so damn satisfying to just lay around at night an tend a fire when camping!