Although I agree with Professor Rushton on the nature of racial differences, I disagree somewhat with his explanation of why they evolved. He thinks a colder climate for those who left Africa 50,000 to 70,000 made the difference. However, agriculture and the earliest civilizations originated in the Near East, which has a fairly hot climate. Also Neanderthals lived for several hundred thousand years in Europe during several ice ages. They seem to have been significantly less intelligent than the modern humans who evolved in Africa 100,000 to 200,000 years ago.
I believe a better explanation for the evolution of racial differences can be found in The 10,000 Year Explosion
, which I reviewed here:
A weakness of The 10,000 Year Explosion
is that it does not explain why Orientals have evolved further than white Gentiles. Agriculture and civilization began later in the Far East than in the Near East. An entire chapter is dedicated to the superior average intelligence of Ashkenazic Jews.
I attribute the greater evolution of Orientals to the Imperial Exam System that existed in China for two thousand years, and to the fact that the Far East never experienced a dark age, similar to what happened in most of Europe when the Western Roman Empire fell.
I still do not understand why the Japanese and South Koreans have higher average IQs than the Chinese.