A lot of people try to argue against paleo nutrition by arguing that the whole world couldn’t eat paleo. First of all, this isn’t even a coherent argument—it’s a fallacy of composition: “paleo isn’t be feasible for everybody, therefore it’s not good for the individual.” But the claim is also false: potatoes, now paleo certified, could easily feed the world. If grains can feed the world, then potatoes can do it better:
Potatoes are more nutritious, faster growing, need less land and water and can thrive in worse growing conditions than any other major crop. They provide up to four times as much complex carbohydrate per hectare as grain, better quality protein and several vitamins – a medium-size potato boiled in its skin has half an adult’s daily dose of vitamin C, for example. They also contain B vitamins, plus many of the trace elements poor people, and grain, lack. (New Scientist)
So if everybody decided to cut grains and switch to potatoes as a staple, then farmers would plant potatoes instead of grains. Over time, potatoes would likely become cheaper due to economies of scale and innovation. (Disease and perishability are the main challenges to potatoes.)
These types of arguments ignore the role of prices and innovation. Increased demand for a good increases its price, encouraging increased production and innovation, as well as substitutes. So even a low-carb, high-meat paleo diet might be possible worldwide. A large increase in demand for meat would lead to a rise in price that would set about efforts to reduce costs through economies of scale and innovations. Furthermore, meat substitutes would also expand to meet the demand (insects are a cheap alternative).