University of New Mexico evolutionary psychologist Geoffrey Miller has said that the quality of sperm is indicative of the brain power in men.
According to the tests conducted by the expert, it was found that men who scored high on a battery of intelligence tests boasted high counts of healthy sperm.
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The finding suggests that intelligence might tip off a man's overall health to women looking for a mate with healthy genes, the researcher explained at a recent Harvard University talk.
"It's not necessarily that the same genes are influencing sperm quality and intelligence," New Scientist quoted him, as saying.
Rather, the two traits could be linked through a tangled web of biological and environmental interactions that has evolved to help women pick a mate.
To reach the conclusion, the researcher and his team uncovered the apparent sperm-intelligence connection after reanalyzing data gathered in 1985 to assess the after-effects of the Vietnam War, particularly exposures to Agent Orange.
Of the 4,402 veterans who participated in three days of physical and mental testing, 425 provided sperm samples.
After accounting for factors that could skew the results, such as age, drug use, and abstinence before providing a sample, Miller's team looked for a statistical link between men's sperm counts and motility and their scores on several tests of verbal and arithmetic intelligence.
Though the connections between brains and sperm were "not awesome, they're there and highly significant," Miller said. All things held equal, good sperm and good brains go together.
Exactly why smart men would have healthy sperm is unclear, but Miller has one idea: "I'm thinking of intelligence as being quite closely related to individual fitness."