Dark Razor: Your assumptions are based on fallacies.
1) Cooking/fire is what divides humans from animals.
2) Certain foods are better for humans than others. Many beans are edible without any preparation, though most are not palatable. Humans are not well suited for consuming simple grain starches and all but Europeans are poorly suited for dairy products (even this group only tolerates dairy).
3) Agriculture is new and not fully tested. We actually ate nuts (high in energy and fat), fruits/berries (high in energy, low in fat), various vegetables (roots (main source of starch), leaves, etc), and meats (mostly fish, followed by red meats, and distantly followed by fowl - most humans preferred to live near water both due to needing water and the fact it contained food). Grains were never consumed by humans before agriculture.