The whole point of being a social animal is that you have behaviour that makes it possible to not only consider other humans as tools for darwinian steps (Eat, fuck, fight) but that we can actually build social networks with more advanced goals.
Caveman struggles to survive between other cavemen. He finds friends. Together, they achieve more. This doesn't mean that everyone needs to be lovey-dovey friends, but by simply working together, you can advance towards goals that are unattainable alone. Say a space shuttle.
The whole point is: Work together, so you can build a better world and you can better kick the ass of that other tribe.
And that's where I completely fail to understand the large and noisy mass of people whom regard the european union with abject fear and loathing. Here we are, slowly making the biggest, baddest tribe to even better kick the ass of the other tribes. And suddenly people squabble. As if a border on a map determine the way your associations are made.