I've thought of it that way, and you do have a point where primal instincts come into play.
However I also believe it's the peoples stubbornness to change, (evolutions says different though >.>) which I guess in a sense racists like the KKK for example, is a part of their culture *shrugs* On a comical note the only way I see everyone combining forces is only during an alien invasion, then again even if we win the fight over a more advance race, we'll bicker on more menial topics such as the fight for oil and so on afterward *chuckle*.
And an amazing quote btw, speaking of Seinfeld I have to go and bump the thread again.