An amazing amount of disinformation and FUD about IQ in this topic from all sides of the debate.
No, IQ was not invented as part of eugenics nor was it invented by Jews. It was slowly developed at the end of the 19th Century by a Gentile British Psychologist working in an upper class boarding school who noticed that pupils who did well in one subject tended to do well in all and likewise that the inverse, those who did poorly in one tended to do poorly in all, was also true.
g, The term that has come from this history, is a term used to describe what can be thought of as the innate "general processing power" of the brain. IQ is a term for a scale that attempts to measure g in an objective, repeatable, and reliable way. IQ as a measure of g seems to bear out that it's not just "intellect" as you might conventionally think of it. IQ correlates with many measures of both short and long term memory, and correlates inversely with reaction time and visual and auditory Absolute Threshold (those who have higher IQs tend to be able to detect dimmer lights flashed for shorter durations than those with lower IQ). There have also been several studies that have found that IQ correlates with what people conventionally define as "intelligent" in that if you put a number of people in the room and ask them to chat with each other and rank everyone in the room on Intelligence it tends to correlate with what IQ tests measure, and the correlation becomes stronger the longer the conversation is.
IQ, in so far as IQ is a reliable measure of the central intelligence factor, g, is a meaningful predictor and is the single most well established and predictively powerful metric in all of Psychometrics. The US Army has found that the more intelligent a soldier is, as measured by the ASVAB which correlates highly with gold standard IQ tests like WAIS and Raven's Progressive Matrices, the more accurate a soldier is and the less likely to become a casualty he is, among other noticeable effects. The Army has likewise also found the corresponding inverse is true. see "McNamara's Folley" lecture on Youtube for more information.
Racial Supremacists, or at least the smart ones, do not see IQ as a single magic bullet that explains 100% of human outcomes on the individual or societal scale, and neither do psychometricians. Factors like Conscientiousness, Agreeability, and other Big 5/Big 3 traits matter a lot, as do specific genes like e.g. the MAOA gene. Another prime factor is Societal Trust, something that relies far more on pure race than it does anything else. A lot more goes into a successful society than just simply intellect, but a certain average intellect is required for a functional society. Think of an IQ >95 as a prerequisite for a first world civilization, rather than a descriptor of why a civilization is successful.
Environment is important, but only in so far as removing massively harmful things like malnutrition and poisoning. A small number of things are conclusively proven to increase IQ slightly, the biggest single one being breastfeeding, but these all cumulatively add to no more than a few points. Also worth noting the environment itself of that a child resides in is also somewhat of a product of genes being that the parents and community are genetically similar to the child.
IQ testing is the strongest and most reliable at around age 24, where it reaches approximately a .85 test-retest reliability. Before age 24 and especially before puberty it's increasingly variable and unreliable. You can safely discard any article claiming a prepubescent person as the smartest anything. After about age 50 IQ begins slowly declining irreversibly, though this decline is arrestable with the usual suspects of good diet, good exercise, and good sleep.
Saying a blanket statement that "Asians and Jews are smarter than Europeans" is incredibly misleading. China cheats massively on these tests and only tests cities, completely ignoring the country side. City states like HK and Macau probably do have IQs circa 103-105, but then you're taking an elite sample. Equivalent to taking the average IQ of Cambridge, Massachusetts and declaring it to be the national average. Same problem with Jews, most tests given to Jewish people are done on university students, a group already selected for IQ. There are also plenty of European groups that test well above 100, and even entire states that are >90% European that test above 100. Montana, for example, has an average IQ of ~105 including the white trash. I've seen studies placing Episcopalians at an average IQ of 115, which is on par with or exceeds what Jews are typically touted to have.
Small changes in the means of a Standard Distribution have massively outsized effects at the tails of the distribution. shifting the mean of a bell curve for IQ 5-10 from 100 to 110 or 90 can result in doubling or halving of the numbers of those with IQs >2 standard deviations outside the mean.
The commonly quoted Flynn Effect, that IQ was rising, is both no longer the case and was an example of IQ being differentiable from g in that g was not rising, only the measurement scale was. g in Europe (or among Europeans rather) has dropped anywhere from a half to a full standard deviation from the Georgian era thanks to the various revolutions murdering huge chunks of the highest end of the scale.
In the modern age of computes, Molecular Genetics studies have begun positively identifying specific genes that correlate anywhere from weakly to strongly. These genes both on their own and in combinations as gene clusters play a huge role in brain development, and do in fact vary among races which is known thanks to things like 23 and me.
This is a very surface level chunk of an information iceberg that can easily change how you think about the world if you choose to spend some actual time reading some actual books with actual sources.
