His conclusions are based on a number of experiments in which worms lived lives of varying debauchery. In an all-male commune, worms were found to die in about 10 days, which was less than if they were allowed female companionship. But if you leave a male totally on his own, he will go on living for 20 days, which is even longer than the usual female lifespan of 16 days.
Dr Gems attributes the short lives of sexually-active male worms to the strain of crawling around in pursuit of women and having to compete with other males and defend their territory. That theory was supported by measuring the lifespans of worms with a genetic mutation that made them pathologically idle. Such dozy male worms lived for 30 days, but - and here is the crucial point - the same genetically-induced laziness in female worms did not result in their living any longer at all.
The conclusion is that males have evolved a naturally longer lifespan than females, in order to compensate for their more active lives. But they are all overdoing it to such an extent that they fornicate themselves into an early grave.
In support of his thesis, Dr Gems mentions two earlier findings. The first was a study in 1969 claiming that eunuchs live for an average of 13.5 years longer than non-eunuchs; the second showed that castrated marsupial mice can live for years, compared with their intact male colleagues who spend five to 11 hours a day copulating and die in just a few weeks.
But to come back to our opening question, have you ever seen a happy castrated marsupial mouse?
Whether the worm research carries over to humans, however, must be highly debatable. First, there is the little problem that most nematode worms - Caenorhabditis elegans, on which the experiments were performed - are hermaphrodite. The females can produce sperm for self-fertilisation; which could easily give a sexually active true male nematode a life-shortening feeling of redundancy.
There is also very little evidence to suggest that sexually hyperactive human males die younger than celibates. Admittedly Mozart's Don Giovanni, who had seduced 1,003 women in Spain alone, was carried off to hell when still in his prime, but Giovanni Casanova, who filled 12 volumes with his sexual conquests and still had time to found the French lottery, lived to the age of 73.
Only this week we have had news of Giulio Paggi, a 101-year-old Italian who has attributed his longevity to "lots of sex". "I still feel like a little boy," he said, "and the secret of this youthfulness is that all my life I've put a lot into lovemaking."
He is not alone in this diagnosis. George Burns, shortly before his death last year at the age of 100, also confessed his secret of long life: "I dance close to young girls and smoke 15 cheap cigars a day."
There is, however, certainly some evidence in the rest of the animal kingdom that sex can damage your health. Anyone doubting this should consult "Head damage due to mating in Ophiogomphus dragonflies", a 1984 paper by SW Dunkle. In that piece of research, however, it was the females who were damaged by sex, when their ommatidia were dented by their lovers' epiprocts.
Lady dragonflies, of course, may have only themselves to blame. Their ommatidia could easily have been dented while they writhed in sexual ecstasy. The injuries might have been prevented by a bit of judicious bondage, as researchers into the sex lives of butterflies and goats have clearly realised. In "Courtship behaviour of the gulf fritillary" (by Rutowski and Schaefer, 1985), experiments were reported in which male butterflies were filmed while courting tethered virgin females, while the previous year an experiment with a tied-up nanny goat had shown that the sexual performance of male goats is enhanced if he knows he is being watched by another male goat or if another male goat has just mated with the same female. Sadly the longevity of the goats and butterflies in these experiments was not recorded.
And before we start castrating our males to give them longer lives, we should consider the results of research on birds which has shown that castrated starlings are liable to become aggressive. It could all be a waste of time anyway, since certain strains of laboratory mice have been shown to be just as active sexually after castration as before it.
But even if sex, with or without bondage, is harmful to the individual, there is no doubt that abstinence can damage the species. Only yesterday, researchers at the Chengdu Giant Pandas Reproduction Base in China were reported to be looking for ways to make giant pandas "enjoy and engage in" sex. "Only 10 per cent of giant pandas are able to mate naturally," one researcher was quote as saying, "so it's very difficult to have them make love and get pregnant naturally."
On the whole, the scientific approach does not encourage us to believe that worm-sex and human sex have a great deal in common. Where scientists cannot proclaim, however, poetry may have its say. In Ted Hughes's Crow cycle, the origin of sex is explained: a worm, who was God's only son, was cut in two, one half inserted into man, the other into woman. The female half burrowed deep and can now be seen peering through her eyes, begging the male half to unify them again: "... calling to its tail-half to join up quickly/Because O it was painful."
And it does, after all, come down to a question of pain. For even if a man's life is longer without sex, what is the joy of abstinence? As Dr Johnson wrote in Rasselas (1759): "Marriage has many pains, but celibacy has no pleasures"