All humans without exception embody a race or a mixture of races. Likewise, all of us embody a gender or a mixture of genders. The first provides superficial, mostly cosmetic physical variation that can affect behavior; the second biologically affects behavior more directly. This parallel invites simultaneous consideration. . Politics however are pure human behavior and all three are imposed by our DNA. Blame your parents ..!
As competitive/social individuals, humans learn to proceed with some caution into uncertainties. Those who do not thus modify their behavior thereby tend toward a lower reproduction rate, reinforcing caution among survivors. A stranger who visibly differs from you and yours raises greater uncertainty for that difference, more so if he exhibits novel language or behavior. That is the simple and obviously necessary root of what we now call racism, as well as of many other aversions. Though generally protective, these aversions carry a cost; in a variable species with varied experience, they are subject to misapplication.
Sexism is no less fundamental: After he and she have accomplished their biological imperative , only she may thereby acquire a growing, long term burden. Her risk is increased by relative size and frailty. Survival of such a species necessarily implies a socially enforced marriage contract and a tendency toward male dominance. The last is being slowly reduced by technology; the former by contraception, abortion and divorce but the biological disparity remains.
The dogs in this manger are the human politicians who pounce upon available differences to enlist support for themselves, magnifying rather than reducing the destabilizing uncertainties. It is notable that whenever a politician is helping one group, it is inevitably at the expense of another, whose members must find their own politicians. It all comes down to selfish misuse of very normal, innate human behavior… and that is very human behavior. To date, it has produced an eminently successful if not necessarily happy species. If the universe offers more, it has yet to be demonstrated. But hope as it is said, springs eternal in the human breast … And that is good, because progress as well as politicians depend upon it.