The evolutionary advantages of a cold climate

I have a running joke about Edmonton—my chilly, difficult, somewhat blighted native city—being the “Cradle of Leadership.” For a little while I was able to tease people about three pillars of Canadian government all being led by people who were significantly soul-struck by Edmonton’s man-killing cold at formative periods in their lives. We had a prime minister whose first political awakening took place here, a central banker who grew up here, and a Supreme Court chief justice who practised law in my neighbourhood. Mark Carney is now at the Bank of England, and Cardinal Ouellet, who ran Edmonton’s Roman Catholic seminary at an adverse moment in his otherwise thrilling rise, came damn close to becoming pope. And, after all, he still might. The world-conquest conspiracy marches on!

I say all this in a spirit of zany autumnal silliness, but the influence of latitude on human populations isn’t a totally silly subject, as any Canadian who has multiple sclerosis—a disease more common almost everywhere as you get further from the equator—will tell you.

A new study in the biometric journal Intelligence presents surprising data from Japan that reveal that IQ, imputed from standardized tests given to a large random sample of Japanese 14-year-olds, varies strongly and persistently with latitude. The Japanese are usually thought of—even by themselves—as being quite homogenous ethnically; the myth of the sturdy, super-cohesive “Yamato race” has not yet been entirely obtruded out of existence. But it turns out that the mean IQs of students in Japanese prefectures apparently vary from north to south by two-thirds of a standard deviation—a spread almost as large as the “race gaps” in cognitive performance which trouble education scholars in multicultural countries like ours. Sun-drenched Okinawans, as a group, do not test as well as the snowbound citizens of Akita.

It is an article of liberal faith that IQ is a bogus tool cooked up by white supremacists to justify imperialism and slavery. I am happy to nod along, but the monsters who developed IQ tests certainly never planned on creating strife between the two ends of Honshu Island. Kenya Kura’s study demonstrates the usual statistical connections between IQ and social outcomes, including physical height, income, and divorce and homicide rates. IQ may be a phony racist artifact, but if shoe size predicted life success as well as those stupid little logic puzzles do, every middle-class parent you know would have one of those Brannock foot-measuring thingies mounted proudly on the wall. That is why IQ persists in the top drawer of the psychometrics toolbox.

There is a funny thing about the Kura study. Thanks to archaeology and DNA, we know that there is actually a hidden ethnic divide in “homogenous” Japan, a bit like what population geneticists find in Britain; on one side of the country people still have some of the characteristic genes of the indigenous Jomon, while on the other you can find hallmarks of more recent invaders from the Asian mainland. This is, however, an east-west split, not a north-south one. The descendants of colonists from China and Korea are still grouped on the Asia-facing side of the Japanese archipelago.

In other words, the IQ gradient seen today is at right angles from the one you would expect given a purely “racial” theory of intelligence founded in known historical migration. The most natural explanation is that natural-selection pressures imposed by latitude—i.e., by diet, sunshine and temperature—have been powerful and fast-acting, enough to blot out any cognitive differences between the “founding peoples” of Japan within about 60 generations.

We tend to think of human nature as permanent—ask anybody gulping a “paleo diet” because it’s “natural” (to “us”). And we generally regard human evolution as something that halted a hundred thousand years or so ago, something not happening now. There is in fact much evidence that evolution has accelerated in the historical timeframe, that evolutionary influences have grown more unequal, and thus more intense, in a world of agriculture, literacy, cities and travel.

We know that in those oddball fringe populations that domesticated milk-giving animals—northern Europeans being only one such group of cheese-chomping weirdos—the genes for adult lactose tolerance took over completely in a shockingly short time, a matter of perhaps two or three thousand years. One implication is that Confucius and Christ and Caesar may be relatively far from us, further than we ordinarily imagine, in purely evolutionary terms. And another is that our descendants may be unrecognizable sooner than we assume.

For more Colby Cosh, visit his blog.