"So, human skin color determines other characteristics?"
If you don't believe that, then you don't believe in racial discrimination. Skin color doesn't directly dictate characteristics. IE an all white or an all black society can and have historically been equally barbarous or ascendant. But mix the two together and something strange happens. The society stratifies according to skin tone. This has happened in many entirely separate cultures (India being a good examples--dark skinned South Indians have rarely ruled over light skinned North Indians). This is clearly not due to some inherent mental defect caused by increased melanin production, but by societal interaction. Placing more trust in light skinned people, and less trust in dark skinned people. Even the Incas were said to be ruled by light skinned (and even blond headed) people, where the Aztecs worshipped some ancient whites they may have encountered as gods (and thus perhaps mistook blond haired, blue-eyed Spaniards for Gods). White skin is bad for you, in that it increases skin cancer. Light colored eyes are bad for you as well, as you more quickly lose your sight in old age. Yet these characteristics have been strongly preserved. There must be a reason for that.
" Too bad IQ tests are a poor indicator of overall intelligence"
No, it is a very good indicator of that. It's just that it correlates almost exactly with skin color, more precisely than with genetics (ie Australian aboriginals and Southern Indians have very low IQs on average, not just Africans, or some certain subset of Africans, as would otherwise be predicted by genetic theory).
It seems to me that skin color causes other people to behave differently towards you. As shown in studies of the perceptions of young children (http://abcnews.go.com/GMA/story?id=2553348&page=1), dark skin is perceived as "bad", "ugly", "masculine", "dishonest" where white skin was perceived as the opposite. Think about how interactions with people who have such genetically defined prejudice against you would effect your development. This is what we call a "self fulfilling prophesy". Kids who aren't trusted tend to be more anti-social--period. This is well known, as kids, including white kids, who get caught in the system tend to remain in it and become ever more criminal. IE they are treated like criminals, so they become criminals.
Failing to recognize these features/biases in human cognition doesn't help anyone. It only hurts us. ALL of us. Most especially the disadvantaged groups we claim that we are trying to help. Fact is: they need to be isolated from white people, because they trust them more than they should, at the expense of their own who are trusted less than they should be, based on individual merit. Communities like Greenwood prospered, until they ran afoul of whites. Then they were annihilated. The current system certainly seems to have failed blacks. Seems like it is time for a change.