I don't see the relationship to the paleo diet. I thought paleo was based on the theory that pre-civilized humans, meaning that they didn't live in static communities (cities or towns) and were nomadic, were hunter/gatherers and ate what they could find. Later when we became civilized and settled into communities we started farming and started growing grains and legumes, which the paleo diet says are bad for us.
Given all that, I find their argument weak considering that humans have been eating grains and legumes for thousands of years with no obvious ill effects. Surely we'd have realized long ago that legumes and grains are bad for us.
A similar "analytical" argument is made for being vegetarian. The argument says that if you examine our teeth and digestive system they most closely resemble the teeth and digestive systems of animals that don't eat meat. Again, thousands of years of meat eating haven't shown any ill effects.
I was vegan for a few years and didn't feel any better. At first I was vegetarian because I was still drinking milk and I did notice that I didn't have the gas that I'd previously had from milk; some interesting interaction there with a mild lactose intolerance it seems.