It's not the main point of the book, but it does describe how it's very hard to live a healthy life on only raw food. I remember it pointing out that about half of women on such diets stop menstruating.

This is something our bodies do out of pretty desperate lack of nutrients, and it's of course devastating from an evolutionary standpoint.

The thesis of the book is that we've cooked food for so long that our digestive system is adapted to it. It even speculates that the shrunken digestive system made our bigger brains possible. All that is far from uncontroversial, but it's a well written and argued text.