It's not 100% the belief that makes races different, of course. I don't believe in equality. I meant to say that that exacerbates it, and makes it such that race is an actual factor, even when it need not be. There are many factors that go into this stuff.
Culture and philosophy is a far better explanatory tool though, especially family culture, and perhaps individual genetic inheritance. These things combined are far more useful and reliable in predicting behavior, values, economic tendencies, and politics.