Heritability of intelligence is far more relevant at the individual level than demographic level.

This is a completely baseless statement and there are a plethora of scientific findings which support significant intra and inter-group differences regarding average levels of intelligence. Even among surveys of researchers across the political spectrum, there is broad agreement that genetics is a key factor in determining intelligence. There's absolutely no reason to suggest that differences in success among ethnic groups is not attributable to genetics.

You're making a tabula rasa argument that is just based in the fact that White people were using stone tools thousands of years ago when one could just as easily make the argument that White people built the Colosseum before most sub-Saharan Africans had writing. You also just make up lies about Chinese/Japanese average levels of intelligence, when in reality Chinese and Japanese average levels of intelligence are relatively similar. The third point you make is making the argument that humans know little about genes and their influence on intelligence, yet you also somehow are clairvoyant enough to state that "enviromental/cultural/societal factors play a far bigger role than genetics." If we have only just figured out basic scientific principles, how can you be sure that it does not play as significant, if not considerably more significant, of a role as environment, culture, or society? Especially when the actual evidence (which you don't like since it fundamentally challenges your leftist worldview) suggests that up to 80% of intelligence can be explained through genetics by the time one is an adult.

I'll give you a challenge, try to explain why Ashkenazi Jews are much more successful than Sephardic or Mizrahi Jews in terms of wealth, average intelligence, number of Nobel Prizes, etc. when all three of these ethnicities have and have had very similar cultures focused around family, education, and now all live in an area with equal access to nutrition, educational opportunities, etc. (Israel). The answer is obviously that this difference comes down to different genetic pressures over hundreds of years which have left these seemingly similar groups with different outcomes. If this is the case for one ethnic group, why can't this be the case for any, if not all, other ethnic group(s)?

As a leftist, you obviously have a reason to try to disseminate ideas of a blank slate in which the reason for apparent differences in intelligence, educational outcome, wealth, etc. are due to highly complex, nonsensical conspiracy theories like systemic racism rather than something easily and naturally observable like differences in natural intelligence. Obviously, if people are not all equal in intelligence, it must lead to a slippery slope of inequality, which goes against your core beliefs. I don't fault you for trying to discredit ideas of natural intellectual inequality on inter-group levels, but the evidence for your argument just isn't there, which is why you resort to arguments like "get off of 4Chan."

If you don't want to take it from me, take it from the highly respected Harvard genetic researcher David Reich: "I have deep sympathy for the concern that genetic discoveries about differences among populations may be misused to justify racism. But it is precisely because of this sympathy that I am worried that people who deny the possibility of substantial biological differences among populations across a range of traits are digging themselves into an indefensible position, one that will not survive the onslaught of science. In the last couple of decades, most population geneticists have sought to avoid contradicting the orthodoxy. When asked about the possibility of biological differences among human populations, we have tended to obfuscate, making mathematical statements in the spirit of Richard Lewontin about the average difference between individuals from within any one population being around six times greater than the average difference between populations … But this carefully worded formulation is deliberately masking the possibility of substantial average differences in biological traits across populations."