Why do People tend to sggregate, differentiate.?

Question:

Why do People tend to sggregate, differentiate.?

While we hate differences due to caste, creed & color, even in the net, the good yahoo has groups and communities- answers community(!!!!) for e.g......... !!!

Best Answer - Chosen by Asker:

insecurities...jealousies...an... fear of the unfamiliar..