What caused the existence of social groups in society?

Man is a social being. Each person seeks to communicate, interact with other people. Social groups are some associations of people with common interests, social characteristics, engaged in similar activities. Social groups have formal or informal rules that govern their activities. The reasons for the emergence of social groups lie in the fact that people always strive for unification, in the desire of people to satisfy their certain needs, in the desire of people to socialize, in the implementation of any similar activity by people.