So the idea of the Paleo Diet — people evolved to eat Diet X, so if we want to be healthy we, too, should eat Diet X — is … intriguingly simple. But, as H L Mencken put it, "For every complex problem, there is a solution that is simple, neat, and wrong."
How is this wrong?
1. Looking at contemporary paleolithic cultures, there is a a vast variety of diets. Paleoliths ate (and eat) what they could in order to survive (long enough to pass on their genes). That, in turn, depended a lot on what was available for them to nosh on.
2. The greatest myth of human health is that there is a perfect human health. The human body is a series of adaptable compromises. Thus, too, diets are an adaptable compromise. There is no perfect diet to perfect health because there is no perfect health. There is just satisfactory (gene-passing-on) health, achieved through satisficing diet.
Which isn't to say that some diets aren't better for you than others, but diets are like investment strategies: it's a lot easier to point to idiocy than to perfection, especially since perfection (fabulous return for no risk) doesn't exist.