Men live in society not because they are men, but because they are animals. The social way of life is a stage in the evolution of life prior to the appearance of the human race.What is distinctive about man is that he had developed social organization far more quickly than any other animal species, so that it is a giant step in complexity between the most elaborate non-human society and the most elementary society of men. Human society shares characteristics with animal societies; it is formed by a given population of individuals, all belonging to the same species. It shows an internal specialization of tasks. Individuals interact as members of the same species and possess one common language which sets them apart from other species. The level of population is perpetuated by means of biological reproduction and of constant struggle against the environment. Similarities like these became conspicuous when human social organization is compared with that of other primates (灵长目).