Assuming that all the benefits you ascribe to eating a primal diet are accurate, have you considered the macro effects on world nutritional levels if this diet was to be globally implemented? Many would argue that current population levels are unsustainable even given a universal grain based diet*. Given that it takes 6 grams of plant protein to produce one gram of animal protein, even if the entire worlds grain production was diverted to growing feed for livestock and vegetables for humans, massive starvation would result. The cost of meat and dairy products would skyrocket, oceans would soon be depleted of edible creatures, the disparity between rich and poor would widen to even greater levels, food riots would erupt and the social disruption would exceed anything depicted in the most apocalyptical disaster movie.
*Sustainability of meat-based and plant-based diets and the environment