As far as I can tell, the debate basically breaks down like this:
1.) There are tons of IQ tests that seem to show statistically significant differences based on race, and they always break down in predictable ways- Back < White < East Asian. Many of these tests try to correct for wealth, geography, upbringing, and so on, and they get these results anyway.
2.) IQ tests are flawed in any number of ways, and we continually revise how we do them. So, old tests become irrelevant based on new standards. So there’s a lot of controversy as far as which tests to count.
3.) Liberals. As usual, they falsify data, call people bigots if they dare disagree, and in general allow politics to mutate science into something horrible. Stephen J Gould was a liar and a charlatan who’s crap about IQ still influences the discussion today. The idea that race doesn’t exist is based on politics, not good science. Most leftists will simply call you a racist and have nothing further to do with you if you say anything (or even hint that you might be thinking something) that goes against what they think about race.
4.) Income. There are also many IQ tests showing statistically significant differences within the same race based on income level. Given that black countries are poor countries and black within other countries tend to be poor, this makes a strong case that the IQ differences are based on culture/economics, and sheds doubts that attempts to correct for that have succeeded.
5.) IQ is going up everywhere. The human species as a whole is getting higher IQ’s, according to tests. Maybe this means we’re getting smarter, maybe it means we’re making the tests easier, who knows. But whatever it means, IQ is going up too fast for evolution or selective breeding to be the explanation. What’s more, races that score lower on IQ tests are improving faster than races that score high.
6.) Most research seems to conclude that intelligence IS influenced by genetics, however. If this is hard science, then all of the studies showing IQ discrepancies based on income level need to somehow account for genetic variation as a factor: are rich populations more intelligent than poor populations because they select for it in their breeding, or despite the genes for intelligence being evenly distributed? Either way, the possibility of race being a factor comes back into it.
Right now I tend to think it’s cultural- there are enough factors within our control that are proven to affect IQ tests, and IQ is changing much faster than genetic drift can account for, so to me the most likely scenario is that there is a connection between race and IQ not because of genetics, but because of the cultures the races tend towards. What is discovered about the general heritability of IQ might change my mind, and more IQ tests on trans-racial adoptees groups might as well.