On a dubious theory of cross-country differences in intelligence

Kanazawa (2007) offers an explanation for the variation across countries of average intelligence. It is based on the idea human intelligence is a domain specific adaptation and that both temperature and the distance from some putative point of origin are proxies for the degree of novelty that humans in a country have experienced. However the argument ignores many other considerations and is a priori weak and the data used questionable. A particular problem is that in calculating distances between countries it implicitly assumes that the earth is flat. This makes all the estimates biased and unreliable.