Even a small difference translates into enormous ratio between numbers of people, several standard deviations from the mean... [...] Yes, and it is defined to have specific standard deviation as well. That definition makes it unsuitable measure. The Gaussian distribution also arises from sum of multiple independent variables. The statement was about intelligence though, which is different thing from both "what IQ tests measure" and "how IQ is defined". Another huge failing of IQ is the non-measure of ability to build and use a huge search-able database of methods and facts. Building such database is a long-term memory task and can not be tested in short time span; the existing knowledge can't be tested without massive influence by the background. Likewise, the IQ test lacks any problems that are actually difficult enough to have some solution methods that some people would know before the test, and some won't. Effectively, the IQ tests do not test for heavily parallel processing capability. For example, I do believe that it would be possible to build 'superhuman AI' that runs on a cellphone and aces IQ tests, and could perhaps deceive a human in brief conversation. The same AI would never be able to invent a stone axe from scratch, let alone anything more complicated; it'd be nothing but a glorified calculator. [...] Well, the people who use skin colour as evidence, i would guess, are on average less well behaved than rest of society... so you can use it to guess someone's criminality or other untrustworthiness.