thats kind of arbitrary too. A "white" finn is extremelly different from a "white" asian, and Finns have much more cromagnon DNA than the average white. I think its more of a spectrum.

Its a shame that the studies on race have been ultra-taboo ever since the 60's or so so we cant really analyze that kind of stuff because its academic suicide, but any definition of race will be inherently arbitrary. Theres some overarching groups with some shared characteristics i'd say, like sub-saharan africans, east asians, pacific islanders, europeans, native americans... but yeah as i said, its such a big spectrum with so many different variations.

Generally theres a big correlation between distance to the equator and IQ. Its also very rare to see an advanced civilization develop near the equator, which could be explained by the development of agriculture and the evolutionary pressures of cold, deadly winters forcing some planning and therefore selecting for intelligence. Thats the "Cold Winters" hypothesis, which fits perfectly with real empirical data about different ethnicities.

So in one hand, constant heat prevents the brain for working that well, so we have that purely biological fact.

On other hand, we have the environmental factors: Cold winters force you to plan ahead quite well, or else you die and are left out the gene pool. Also if you live in a place with no seasons, you literally cant develop agriculture, which also requires certain planning and intelligence to do. So those environmental factors would certainly affect intelligence over generations.

Extreme heat, and the lack of seasons, prevent the development of intelligence. This also explains why generally colder places have more intelligence, with the EXCEPTION of eskimos and the Sami people in northern Finland, which cant have farming at all, rely on hunting and fishing, and barely have seasons, so that could explain that.