A few days ago I was thinking about one of the most provocative Damned Facts from population genetics, and came up with a prediction that as far as I know nobody has uttered or tested before. I throw it out here because someone with access to the right kind of primary data might be able to test it.
Here’s the Damned Fact: the measured average IQ of breeding populations varies inversely with the average temperature to which their ancestors were long-term adapted. Anthropologists who have studied the matter believe this is because cold climates put more of a premium on tool use and long-term planning than hot ones. A New Guinea tribesman can farm, hunt, and survive year-round naked with nothing but a spear and a digging stick; an Inuit requires complex clothing, ice shelters, and elaborate space-framed boats.
Note that “environment of ancestral adaptation” is not the same as where people live now; if the latter were true we might expect that Inuit would have the most impressive average IQ on the planet, but they expanded into the high Arctic only within the last millennium or so. Inuit do, interestingly enough, seem to have a freakishly high average of mechanical and 3-D spatial ability relative to other populations, but it is unknown whether this is genetic or due to some kind of training effect of their environment.
(My suspicion is that it’s genetic, but not because a thousand years is enough to select for it. Rather, my guess is that Inuit are descended from a small founder population that was able to colonize the high Arctic precisely because it already had those traits.)
A quality that has not been as well studied as IQ is “time preference”. People with high time preference discount future rewards in favor of present ones; conversely, people with low time preference more easily defer rewards and invest now to capture higher gains later. Time preference has mainly been studied by economists and sociologists rather than anthropologists and, as far as I am aware, nobody knows to what extent variations in it are genetically rather than culturally transmitted.
One thing that is known about IQ and time preference is that they correlate inversely and fairly strongly. Economists have studied both IQ and time preference as predictors of the wealth of nations. As one might expect, wealthier countries exhibit higher average IQ and lower average time preference (the latter being reflected in comparative savings rates).
This sets up my prediction: if the distribution of time preference by breeding population is studied carefully enough, it will be found to be as strongly correlated with temperature in the ancestral environment as IQ is. Furthermore, that correlation will be largely independent of IQ variation – that is, it will still exist if variations in IQ are statistically masked out.
Here’s why I think so: as a pre-industrial human in cold climates, you get a survival reward for doing things that are more difficult if you have high time preference – most notably, saving food and other resources that you might consume now for later when they are more difficult to obtain. The main feature of colder climates drive this need is larger seasonal variations in food availability and (in very cold climates) the critical importance of hunting.
In hot climates, plant food and game animals are abundant year-round. The value of saving food is low, and the climate makes preserving it difficult. At higher latitudes and lower average temperatures, seasonal variations in availability both become significant and saving food increasingly necessary. In Siberia and the Arctic, crops won’t grow at all; indigenes must live by hunting and storing food.
There you have it. A question for some enterprising scientist to look into. I suspect the primary data has already been collected and just needs the right statistical questions put to it.