Paleontological evidence suggests that meat constituted a substantial proportion of the diet of even the earliest humans. Early hunter-gatherers depended on the organized hunting of large animals such as bison and deer. The domestication of animals, of which we have evidence dating back to the end of the last glacial period (c. 10,000 years BC) allowed the systematic production of meat and the breeding of animals with a view to improving meat production.
Increased meat-eating has followed rising affluence in many parts of the world. China's levels, for example, increased from 3.6 kg consumed per person in 1961 to over 60 kg in 2013. Half of the world's pork is now consumed in China.
According to a study made by the University of Graz in 2014, vegetarians are more often ill and have a lower quality of living than meat-eaters. The study also says that they show more psychological disorders than meat eaters.
Big meat-eaters were also found to have a “significantly better quality of life in all categories”, the study found. The four categories examined were: physical and psychological health, social relationships and environment-related life quality