> People are kept separate

Good point. And they "self segregate" themselves too? If there're two kids, and one is a lot brighter than the other, i think both of them will tend to get frustrated when playing together or deciding what to do -- so they'll find others to play with.

Maybe this a bit applies to emotional intelligence too.

One's whole life, one a bit chooses people with similar "capabilities", without thinking about it?

And then, from time to time, one sees in the newspapers what the vastly different people do, and get surprised: can there really be such people, where are all those people