Past studies have linked an individual’s intelligence to his or her height, cardiovascular function and longevity, but now a new study suggests semen quality may be added to that list, since it also appears to help predict the level of a man’s intelligence.The findings as a whole suggest that both intelligence and semen quality are fitness traits — characteristics evolved to promote survival — that are influenced by genetics.
Researchers at London’s Institute of Psychiatry have found that more intelligent men have better quality sperm, suggesting a correlation between intelligence and evolutionary fitness, in a study published in the journal Intelligence.
The research team embarked on the study to test the hypothesis that more intelligent people were healthier, not only due to lifestyle factors, for example that brighter people are less likely to smoke, but in an underlying genetic sense. Some research has rather controversially suggested that intelligence and sperm quality are linked, which historically has served the purpose of putting clever men at an advantage in reproductive terms.
The study analysed 425 former US soldiers, who had served in the Vietnam War, and who had provided semen samples and undertaken intelligence tests. After adjusting for lifestyle factors, it was found that the more intelligent men both had more sperm and sperm that could swim better. Researcher Rosalind Arden stated, ‘we found a small positive relationship: brighter men had better sperm. This association wasn’t caused by habits like avoiding smoking or drinking – the big hitters of health’.
However, researchers have emphasised that the relationship between intelligence and sperm quality is small, and that it does not mean that bright men are more likely to have more children, nor that undertaking brain-training games was likely to improve sperm quality. Arden commented, ‘this does not mean that men who prefer Play-Doh to Plato always have poor sperm: the relationship we found was marginal’.
Meanwhile, the team are now interested in the relationship between overall physical health and intelligence, the ‘fitness factor’ idea, which suggests that there might be an underlying relationship between many genetic factors in order to improve chances of longevity and reproduction. ‘We were interested in testing the idea that if most of our genes act on many characteristics there might be a weak but discoverable relationship right across all of our characteristics – from nose to toes’, explained Arden.