> What if some of the observed racial differences were caused by a lack of vitimin D, due to darker skin photosynthesising less of it? Vitamin D is essential for brain development. Black people in northern climates get less of it than evolution intended. This lack of vitamin D might be causing reduced brain development in black populations. If that is true, we could fix the prison crisis and racial IQ differences with a pill!

Well, that would be knowable from a study of Vitamin D levels in the incarcerated population vs non-incarcerated among those with the same skin tones. I don't see any reason to bring IQ into this, nor race (vitamin D absorption is tied to skin tone, so a dark skinned person of Indian descent is as likely to have vitamin D deficiency as one of sub-Saharan African descent).

> If we block all research into a problem then we can’t solve it.

Establishing or refuting IQ differences among "races" is simply not a problem. It is sought after, at best, as a scapegoat, to deny any responsibility of racism in the measurably worse outcomes of people with certain heritage than others. Refuting race-IQ genetic correlation would simply eliminate this scapegpat, that most scientists don't actually believe in; while confirming it would just mean the problem is hopeless and nothing can be done to improve the situation.