Balls and brains

That's The Economist's headline:
The quality of a man’s sperm depends on how intelligent he is, and vice versa

THERE are few better ways of upsetting a certain sort of politically correct person than to suggest that intelligence (or, rather, the variation in intelligence between individuals) is under genetic control. That, however, is one implication of a paper about to be published in Intelligence by Rosalind Arden of King’s College, London, and her colleagues. Another is that brainy people are intrinsically healthier than those less intellectually endowed. And the third, a consequence of the second, is that intelligence is sexy. The most surprising thing of all, though, is that these results have emerged from an unrelated study of the quality of men’s sperm.

[. . .]

Ms Arden found 425 cases where samples had been collected and analysed from unvasectomised men who had managed to avoid spilling their seed during the collection process and had answered all the necessary questions for her to test her hypothesis, namely that their g values would correlate with all three measures of their sperm quality.

They did. Moreover, neither age nor any obvious confounding variable that might have been a consequence of intelligent decisions about health (obesity, smoking, drinking and drug use) had any effect on the result. Brainy men, it seems, do have better sperm.

By implication, therefore, they have fitter bodies over all, at least in the Darwinian sense of fitness, namely the ability to survive, to attract mates and to produce offspring. That is an important finding. Hitherto, biologists have tended to disaggregate the idea of fitness into a series of adaptations that are more or less independent of each other. This work adds to the idea of a general fitness factor, f, that is similar in concept to g—and of which g is one manifestation. To him that hath, in other words, shall be given. Unfortunately for the politically correct, Dr Miller’s hypothesis looks stronger by the day.

Dienekes links to the study. While the result has no direct bearing on Rushton's cross-racial claims (which stand or fall on their own merits), it seems to contradict the broader theoretical underpinning of Race, Evolution, and Behavior, proving that intelligence and reproductive potential need not be inversely related in humans (at least in men).

Related: Physical correlates of cognitive ability


Anonymous said...

In no way would such a study refute or contradict Rushton, as Rushton merely compiles data and formulates generalizations (albeit politically incorrect ones) based on the data. I suspect Rushton contradicts your political worldview in some way, as you have attacked him before.

Smart guys may have better quality sperm on average than dull guys, but human sexual selection is a complex process, with lots of different variables, and the fact that we live in a world radically different from the one our prehistoric ancestors lived in will mean those that thrived then will not necessarily thrive today.

Also, females are not so one-dimensional that they will only look at one trait (e.g., intelligence) and pick that because a science paper or whoever writes it says they should. Attraction is not a rational process.

It's interesting that you mention Geoffrey Miller, because I came to similar conclusions as him independently. I stopped reading "The Mating Mind" because I felt he put too much emphasis on sexual selection in shaping human intelligence.

I think sexual selection played a role, and I've thought about elaborating on this topic which clearly deserves more attention from the scientific community with my own blog or website.

Anonymous said...

Rushton merely compiles data and formulates generalizations (albeit politically incorrect ones) based on the data.

The whole idea behind REB is that "r-K" theory, applied among humans, explains a host of racial differences. In service of this argument Rushton sometimes omits and (once, that I know of) invents data. Rushton is generally admired by people who broadly-speaking share my "political worldview", among whom he has inspired much sloppy thinking, compelling me to respond on occasion.

It's the application of the r-K framework to humans that this study tends to undermine:

The r and K strategists differ in the number of eggs they produce. The r-strategists are like machine-gunners. They fire so many shots that at least one of them will hit the target. The r-strategists produce many eggs and sperm, and mate and give birth often. The K-strategists, on the other hand, are like snipers. They put time and effort into a few carefully placed shots. K-strategists give their offspring a lot of care. They work together in getting food and shelter, help their kin, and have complex social systems. That is why the K-strategists need a more complex nervous system and bigger brain, but produce fewer eggs and sperm. [p. 34, Race, Evolution, and Behavior (abridged edition)]

I see little to disagree with in the rest of your comment.

I've thought about elaborating on this topic which clearly deserves more attention from the scientific community with my own blog or website.

Go for it.