>>14143852>he actually believed in the cold winter theory meme Protip: Inuit Eskimos are northern most population with the largest cranial sizes. Yet their IQ average is around 93. Environmental pressures concerning surviving the cold is more about the development of brown fat to maintain body temperature not brain size.
IQ is more influenced by nutrition intake, population dynamics (mate selection, genetic bottlenecking) and rigorous exposure to reading/writing. It's a very good chance that the baseline concerning IQ differences is more the result continuous genetic bottlenecks via constant migration from one region to another with then nutrition and reading/writing as supplemental to IQ.
This would explain how for instance Aboriginal Australians (60-65) have IQs lower than surrounding Malaysian populations and even most African populations, because the particular genetic bottleneck episode went against them. While the Han Chinese got higher IQs (100-104) despite the surrounding ethnic Chinese (80-93) having lower in comparison.