Men of higher intelligence tend to produce better quality sperm, British research suggests

A team from the Institute of Psychiatry analysed data from former US soldiers who served during the Vietnam war era. They found that those who performed better on intelligence tests tended to have more - and more mobile - sperm. The study, which appears in the journal Intelligence, appears to support the idea that genes underlying intelligence may have other biological effects too. Therefore, if tiny mutations impair intelligence, they might also harm other characteristics, such as sperm quality. Conversely, people with robust genes might be blessed with a biological "fitness factor" making them fit, healthy and smart. Previously, scientists tended to assume that lifestyle factors were more likely to underlie any relationship between intelligence and health. For instance, brighter people may be less likely to smoke, and more likely to take exercise, both of which are known to impact on mental performance. The latest study tested the gene theory by taking two characteristics that seemed unlikely to be associated with each other - intelligence and sperm quality. They found a small, but statistically significant link, and were able to show that this could not be explained by unhealthy habits, such as smoking or drinking alcohol. The study was based on 425 men who undertook several intelligence tests and provided semen samples. The researchers found that independently of age and lifestyle, intelligence was correlated with all three measures of sperm quality - numbers, concentration, and ability to move.