People are social animals and highly socialized species. Human gregarious is not a family unit like a lion, but a more complex collection of multiple families (or people). In the process of evolution, human beings rely on cooperation to resist natural enemies and collect food, and gradually form the socialized species habit of "modern people".

The so-called social animals:

The current definition is that the lifestyle is characterized by groups, which generally refers to the same species, that is, what we call animals that live together in groups and help each other in hunting, eating, sleeping and other lives.

So it can be seen from this definition that human beings are no longer familiar with each other. We are all together, from a small family to a big country, from a human being on the earth, all belong to a human species, and we can all have cooperative relations, but the wider the scope, the smaller the form of this cooperation, or even it doesn't matter.