“The really sparsely populated regions where there is plenty of game to go around, according to Chagnon, tend to be the most violent regions. So Chagnon thinks that if anything this is because the more protein you have—this is one of his theories—the more well-fed you are, the more energy you have for this kind of sport. The Yanomamo see warfare as this: the more they’re struggling just to feed themselves the less energy they have for warfare.
Moreover, war is just not something that you see when you go back into human evolution. And culture, in fact, can also help us overcome this very destructive behavior.”
The more protein you have, the more energy you have for the sport of war. Does that make out a case for vegetarianism? In Hinduism we have a concept called satvic food that is essentially food that is supposed to reduce aggression and promote harmony and peace. Excess of animal proteins is believed to promote unnecessary aggression and bellicosity.The Hindu sanyasi (recluse) shuns non-vegetarian food and alcohol and practises abstinence. Traditionally the kshatriyas(warrior class) and the shudras(peasants) are non-vegetarians because their professions demand aggressiveness and physical strength while the brahmins(priests) and the vaishyas(traders) who have to be peaceful and accommodative and demand less physical strength are vegetarians.
But all that is a hypothesis .More reseach may be required to link excess of protein to aggressive behavior.