Humans seem to have natural instincts that make them want to set up a pecking order, reject people, accept people. Hate, contempt, joy, hubris, anxiety, all these emotions have some sort of purpose that we evolved.

What are the mechanics of it? Feeling disgust at the smell of putrecine is a text book example of an instinct, it is simple like 1+1=2, other instincts are more complicated and more difficult to put a pin on but they are there. Has anyone ever done a study of this?

Discuss.