Not all orgasms are created equal. For instance, intercourse orgasms are known to trump masturbatory ones, as evidenced by the amount of dopamine and prolactin produced. For men, sexual excitement produces higher sperm counts. As I recount in BLONDES, men who felt jealous or threatened by the possibility of a cheating partner had higher sperm counts than men who did not. The same is also true of male porn-watchers masturbating to a threesome. When guys watched two men attending to one woman, they had higher sperm counts than when watching one-on-one sex.

Sperm competition is the reason, according to the notorious British biologists Baker & Bellis. Men produce more copious, higher quality semen in situations in which those sperm might compete with rival sperm from other males.

And now there’s more — speculation that beautiful women also inspire men to have better quality sperm.

Female beauty has been found to enhance male sperm quality in other species. The latest evidence comes from a study led by Oxford biologist Charlie Cornwallis on Gallus gallus, a species of bird. Cornwallis and his colleagues discovered that the comelier the chick — e.g., plump with an elaborate comb — the better the quality her partner’s sperm (more motile, higher velocity, with a higher sperm count). Interestingly, this was true of dominant males but not subordinate ones, who appeared to put everything they had into every copulation. From Cornwallis’ perspective, the most fit males invest their best loads in the most reproductively fit females.

No study has yet proven that the same is true in humans — it’s not exactly ethical to recruit a guy to have sex with both a beauty and a plain Jane and then compare the aftermath. A beauty bias that affects sperm count may be true only in a wildly polygamous species, which humans are not.

Even so, this theory applied to humans doesn’t sound so controversial if you think about it — after all, sperm counts in men are associated with sexual excitement. Beauty can spark frisson. Even more exciting to ponder is how in practice an alpha male would make a larger reproductive investment in the most desirable mate. How does a Hugh Hefner decide? And wouldn’t it be ironic if this were true?

Evolutionary psychologist Geoffrey Miller, author of The Mating Mind and the famous stripper study described in BLONDES, recently found another interesting connection: smart men have better sperm.

Analyzing the data of 425 veterans who took IQ tests and submitted sperm samples, Miller found a statistically significant link between men’s IQ and their sperm quality (higher scorers had higher sperm count and motility). Miller is the biggest propagator of the theory that intelligence is a sexually selected trait. Women, the choosier sex, are attracted to intelligence — expressed in anything from problem-solving to songwriting — because it’s a sign of “sexy” high-quality genes and overall developmental fitness. And because a woman can’t test a man’s sperm directly for these qualities, she has to judge him by what comes out of the head sitting on his shoulders.