Christians always get dumped on for being anti-evolutionists but I am astounded how evolutionary principles like nature selection and survival of the fittest are routinely denied by "enlightened" liberals for the same inexplicable reasons. The paleo diet is the present case in point. If we eat alien food that we have no real ability to process then we get horribly fat and sick.
On the contrary; it's merely that I'm in favor of rational and correct application of evolutionary principles, not naive or simplistic ones.
e.g., "Clearly, if the carbohydrate-rich diet of our ancestors implemented 10,000 years ago was in discordance with their physiology, then this would have created a selection pressure for evolutionary change in some features of human metabolism. Given this, modern humans – especially Europeans, the descendants of simple agriculturalists which had consumed cereal grains for 400–500 generations – should be in some way ‘adequately adapted’ to carbohydrate-rich diets. However, if Kopp is right and there was no ‘adequate adaptation’ since the end of the Pleistocene, then the carbohydrate-rich diet was functional without it. Whatever is the fact, to think that a dietary factor is valuable (functional) to the organism only when there was ‘genetical adaptation’ and hence a new dietary factor is dysfunctional per se because there was no evolutionary adaptation to it, such a panselectionist misreading of biological evolution seems to be inspired by a naive adaptationistic view of life"
Ströhle, A., Woltersa, M., & Hahn, A. (2007) Carbohydrates and the diet–atherosclerosis connection—More between earth and heaven. Comment on the article “The atherogenic potential of dietary carbohydrate.” Preventative Medicine, 44, 82-84.
It's of course true that fake food is bad for you and any diet that discourages it is a step up. But, that doesn't relieve the premises of the "caveman diet" from their error.