People band together into groups when threatened from outside. Whether we are talking about Hutu's and Tutsi's in Rwanda, Protestants and Catholics in Ireland, Shia and Sunni in Iraq, black and white in New Orleans, tribal behavior, loyalties and excesses are all too apparent.

Tribes live together, develop language variations, create distinctive art and engage in social customs. Loyalty is demanded and given freely. Tribes take care of their own.

Tribes avoid assimilation into the larger culture.