Every country seems to have a North-South divide. In Britain the divisions are perceptible and deeply felt. Health and wealth fall off sharply once you cross an oblique line of separation mid country. Italy is another exemplar of North-South divisions. Garibaldi has a lot to answer for. Now Ken, as Kenya Kura modestly and helpfully calls himself when speaking to Western audiences, has had a look at his home country of Japan.
Ken begins on a typically bold note: Those who have adapted to the harsh northern climate worldwide are taller, more intelligent, more pro-social, less crime prone, and exhibit less fertility. This is said to be due to the more cognitively demanding long winter season (Lynn, 2006 and Lynn, 2008). In a similar and more speculative vein, the differential r/K theory (Rushton, 1988 and Rushton, 1994) predicts that a more demanding cold climate has induced more intelligent and pro-social personality in general.
Regional differences in IQ are estimated for 47 prefectures of Japan. IQ scores obtained from official achievement tests show a gradient from north to south. Latitudes correlate with height, IQ, and skin color at r = 0.70, 0.44, 0.47, respectively. IQ also correlates with height (0.52), skin color (0.42), income (0.51) after correction, less homicide rate (− 0.60), and less divorce (− 0.69) but not with fertility infant mortali’ty. The lower IQ in southern Japanese islands could be attributable to warmer climates with less cognitive demand for more than fifteen hundred years.
He then tests this out on the prefectures of Japan.
The prefectural IQs have been calculated from the national achievement survey uniformly conducted by the government with 11 and 14 year old students. Students at these ages are in their last year of compulsory elementary and junior high school, respectively, in Japan.
The analysis utilized the simplest index of prefectural IQs, the sum of the math subtest scores and verbal subtest scores for those five years (full score = 482, average = 323.5, standard deviation = 102.9). These scores were obtained from more than 4 million students, which account for more than 3% of the whole population.
Latitude is correlated with IQ (r = 0.44) and height (r = 0.70). From many collected IQ measurements, the Japanese average IQ has been estimated to be 104, which is slightly lower than the Chinese and Korean averages (Lynn & Vanhanen, 2006; Lynn, 2008,Lynn and Meisenberg, 2010 and Lynn and Vanhanen, 2012). Assuming that the Japanese population has a standard deviation of 15 as in England, north–south IQ difference is estimated to be 11 points, with the prefecture with the highest IQ prefecture (Akita) having 107 while the one with the lowest (Okinawa) having 96. This is surprising in that it challenges the much-touted homogeneity of Japanese people.
Many people worldwide seem to have an image of Japan as a highly homogeneous nation. However, the Japanese islands were initially populated by the hunter–gatherer Jomon people (Y haplogroup C1, C3 & D1) and experienced a great deal of immigration from the Korean peninsula and mainland China from 2900 to 1500 years ago. These incoming Yayoi people (Y haplogroup O2b from Korea and O3 from China) brought wet-rice agriculture and bronze and iron tools to the islands. Because of these cultural advancements, they had shown much more fecundity and have in number dominated the native Jomon people. There still exists a genetic cline from the Western Yayoi population in the Eastern Jomon population in Japan (Hammer et al., 2006). Haplogroups, C1, C3 and D2 are most common among the Ainu people in the northmost Japan (almost 100%) and in the Okinawans in southmost Japan (about 60%),while the western regions closer to the Korean peninsula are more densely populated by Yayoi descendant haplogroup of O2b and O3 (60–70%).
Since the continental Northeast Asians (Han Chinese and Korean) have a higher intelligence compared to the rest of the Eurasian population, it would be natural to assume that these Yayoi people were more intelligent. This conjecture is based on the facts: 1. The fossil evidence shows that the Yayoi people were 5–8 cm (2–3 in.) taller than the Jomon; 2. Modern-day Koreans are about 3 cm (1.2 in.) taller than the Japanese; 3. The IQs of Chinese and Korean people have continuously outscored that of Japanese people (estimated to be 106 and 105, respectively). Hence, it is reasonable to expect that the prefectures closer to the continent exhibit higher intelligence than those in the Northeast.
However, this tendency was not observed and instead there exists a simple intelligence gradient from south to north. This may be due to an almost perfect admixture within the last 1500 year (about more than 60 generations) as far as genes for taller stature and higher intelligence are concerned, as well as the selective pressures of the last 1500 years of civilization, which have been strong enough to reshape the original east–west IQ gradient into the current north–south cline. This conclusion would be in line with the Hawks, Wang, Cochran, Harpending, and Moyzis (2007) idea of ever-accelerating human evolution. They insist that more and more beneficial mutations swept populations, after the advent of agricultural civilizations with metallurgy, letters and complex hierarchical organizations. The Japanese north–south gradient in height and intelligence can be evidence that modern humans have evolved to higher intelligence within the last two millennia.
In brief, it appears that if humans (or at least the Japanese ones) are cooled down a bit, and the imprudent ones killed off by hard winters, then the survivors are brighter, milder, lighter-skinned and more suicide prone, more socially-conscious and law abiding, divorce less often and have fewer children. Can such Northerners survive the global battle of the cradle, or will they be marginalised and driven further north, to die in the frozen wastes?