I don't get why paleo diet is not congruent. So our DNA is build upon iterations(generations), and the aliments that were eaten in the majority of those are better suited for our current generation.
Valid for what? You have no obligation to eat what your ancestors ate. Our ancestors certainly didn't, which is why they didn't eat like single-celled organisms. If what you are thinking were true, it would be true for them as well.
Not to mention the fact that your food has evolved as well.