Although it is widely held that infections and eating difficulties are hallmarks of advanced dementia,25 there are few prospective data on the incidence of these complications. Over the course of 18 months, more than half of the residents in our study had infectious episodes, and 86% had eating problems.
So 10 billion people is the uppermost population limit where food is concerned. Because it's extremely unlikely that everyone will agree to stop eating meat, Wilson thinks the maximum carrying capacity of the Earth based on food resources will most likely fall short of 10 billion.
There have been a large number of published estimates for the human carrying capacity of the earth; they range from a low of one half billion people to a staggering 800 billion. Many of these estimates are more ideologically based than determined by scientific principles2.