Smart men are sexier: come on now, we all know that. However, scientists are now making a more ambitious claim, that smart men are more virile:

Psychologists have found that men with the highest IQ also have the healthiest sperm.

That claim to me rests on much less sound foundations.

OK, as to the intelligence leading to sexiness: well, intelligence is a survival trait. Those who have it do tend (and have throughout the history of our species) to survive and to breed better than those without such intelligence. Thus, by definition, it’s a sexy thing to have.

But to then go on and claim that because of intelligence that men are more fertile, that they have better sperm, seems quite a leap. The finding was done by looking at sperm samples from Vietnam era vets alongside their intelligence tests. There certainly was a correlation between the two, so that would seem to seal it, yes?

Well, no, for while correlation might imply causation it doesn’t prove it. I think what they’ve missed is that there are other possible causes here.

This is something that all too many of us forget (if we ever knew). It’s only in recent decades that everyone has actually had sufficient calories during their upbringing. Diseases of malnutrition, like scurvy (no, really!) and rickets were quite common in my native England only 60 years ago. The Southern states of the US were famous for pellagra. And I think that this is where the link between intelligence and virility might come from.

Remember that Vietnam vets would have been born in the great post-war baby boom. And also remember that the middle classes could largely get out of conscription in that war if they wanted to. It was largely the poor, especially the urban poor, that ended up going. The urban poor being the most likely to be, even partially, malnourished in childhood.

And we also know very well that malnourishment in childhood can indeed lead to less than optimal mental development: even if it’s only the lack of trace elements. Similarly with other developments, including that of fertility.

So I have a feeling that this research is suffering slightly from not considering alternative explanations for the correlation they have found.