Social brain ho & Social intelligence

There is three hyperthesis about Big Brain, encephalization quotient. first, Fruit diet second, extractive food source. last, it is social brain hyperthesis. Why the human have Big Brain? The reason can account for next. The human need to various relationships and alliances with each other. If someone has brain smaller than animal's brain(monkey, rhino etc.), he or she cannot survived in the world. Survival is important. It is reason for existence. In view of same point, Social brain is more and more span, Human's social intelligence is bigger than other animals.