It occurred to me recently, under conditions that I leave to your ample and likely sordid imagination (how dare you), that the very concept of "premature ejaculation" in human males is a strange one, at least from an evolutionary theoretical perspective.


After all, the function of ejaculation isn't really a mysterious biological occurrence…it's an evolved mechanism designed by nature to launch semen, and therefore sperm cells, as far into the dark, labyrinthine abyss of the female reproductive tract as possible. And once one of these skyrocketed male gametes, in a vigorous race against millions of other single-tasked cells, finds and penetrates a fertile ovum, and—miracle of miracles—successful conception occurs, well then natural selection can congratulate itself on a job well done.

So given these basic biological facts, and assuming that ejaculation is not so premature that it occurs prior to intromission and sperm cells find themselves awkwardly outside of a woman's reproductive tract flopping about like fish out of water, what, exactly, is so "premature" about premature ejaculation? In fact, all else being equal, in the ancestral past, wouldn't there likely have been some reproductive advantages to ejaculating as quickly as possible during intravaginal intercourse—such as, oh, I don't know, inseminating as many females as possible in as short a time frame as possible? or allowing our ancestors to focus on other adaptive behaviors aside from sex? or perhaps, under surreptitious mating conditions, doing the deed quickly and expeditiously without causing a big scene?


Like so many things before, it turns out that this insight of mine was actually several decades behind the curve, because in 1984, when, at nine years of age I was still anything but a premature ejaculator, a sociologist from California State University named Lawrence Hong published in the Journal of Sex Research a highly speculative, but very original, paper along these same lines, fittingly titled "Survival of the Fastest: On the Origin of Premature Ejaculation." In this article, Hong—whose most recent work, so far as I can tell, has been on the global phenomenon of cabaret transgenderism—posited that, during the long course of human evolutionary history, "an expeditious partner who mounted quickly, ejaculated immediately, and dismounted forthwith might [have been] the best for the female."

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The empirical centerpiece of Hong's arriving at this conclusion is the fact that, on average, human males achieve orgasm by ejaculating around just two minutes after vaginal penetration, whereas it takes the owners of these vaginas, on average, at least twice that long to do the same once a penis is inside of them — if they achieve orgasm at all, that is. This obvious gender mismatch between orgasm latencies can be understood, Hong reasons, only once we acknowledge the fact that sex evolved for reproductive rather than recreational purposes; don't forget, he reminds us, that sex for sex's sake is a relatively recent technological innovation enabled by prophylactics and other modern contraceptive inventions.

The author compares the mating habits of human beings to other rapid—and not-so-rapid—ejaculators in the primate family, noting that the faster a primate species is in the coital realm, the less aggressive it is when it comes to mating-related behaviors. He calls this the "slow speed — high aggressiveness hypothesis." For example, male rhesus macaque monkeys often engage in marathon mounting sessions, where sex with a female can be drawn out for over an hour at a time (including many breaks and therefore non-continuous thrusting). That may sound great, but libidinous anthropomorphizers beware: macaque sex is a chaotic and violent affair, largely because the duration of the act often draws hostile attention from other competitive males. By contrast, primate species whose males evolved to ejaculate rapidly would have largely avoided such internecine violence, or at least minimized it to a considerable degree.


Key to Hong's analysis therefore is the idea that intravaginal ejaculation latencies in males is heritable—there was initially greater within-population level variation in the male ancestral population, he surmises, but over time, "the ancestry of Homo sapiens became overpopulated with rapid ejaculators." This is because, according to Hong, young reproductive-aged males who ejaculated faster (i.e., had more sensitive penises) avoided injury, lived longer and therefore had a greater chance of attaining high status and acquiring the most desirable females.


Hong's reasoning on these heritability grounds has in fact received very recent support. You may have missed this in your monthly periodical readings, but in a 2009 article from the International Journal of Impotence Research, a team of Finnish psychologists led by Patrick Jern of Åbo Akademi University reports evidence from a large-scale twin study showing that premature ejaculation is determined significantly by genetic factors. So just as Hong surmised in 1984, this is indeed a heritable trait—if you doubt it, go on, have that awkward conversation with your fathers, boys. In fact, since Jern and his colleagues found that delayed ejaculation—the other extreme end of the ejaculation latency continuum—revealed no such genetic contributions, these authors generally agree with Hong, postulating that "premature" ejaculation may be a product of natural selection whereas delayed ejaculation "would be completely maladaptive." Delayed ejaculators are considerably rarer, with a prevalence rate as low as 0.15% in the male population compared to as high as 30% with premature ejaculators, and their condition is usually owed to lifelong medical conditions or the recent use of antiadrenergics, selective serotonin reuptake inhibitors (SSRIs), neuroepileptics, or other modern-day drugs that, I say blushingly from personal experience, are often associated with anorgasmia as a miserably unfortunate side-effect.

Adding additional credence to the evolutionary model is a separate set of self-report data published by Jern and his colleagues last year in the Journal of Sexual Medicine, in which ejaculation latencies were shown to be significantly shorter when men achieve orgasm through vaginal penetration than when doing so in the course of other activities, such as anal, oral, or manual sex. In fact, in light of these differential ejaculation latencies, the authors argue that the very construct of such male orgasmic "timing" is best carved up by discrete sexual behaviors rather than treated as a more general clinical phenomenon. And they offer several helpful acronyms for these ejaculation latency subtypes, too, such as "OELT" for "oral ejaculation latency time" and, conveniently, "MELT" for "masturbation ejaculation latency time."


I have the niggling, faraway sense that we've left something out of the evolutionary equation regarding the variation in male ejaculation latencies. What, oh what, can that possibly, conceivably be? Ah, right—women's sexual satisfaction. Oh come now. Actually, Hong didn't leave female orgasms out of his rather viscous analysis altogether; he just didn't see it as being central to selective pressures. Presumably, like other theorists of that time writing about the biological reasons for female orgasms (such as Stephen Jay Gould, who thought that female orgasms were much like male nipples, a happy leftover of the human embryological bauplan) he saw women's sexual pleasure as being a nice, but neither here nor there, feature of human sex that nature had thrown into the mix. And, anyway, writes Hong, for women, as a general rule, "genital sex is better with digital sex":

The tender touch, the passionate caress, the gentle rub, the titillating probe, and all those other infinite maneuvers that humans, as the most sophisticated bipedal primate, are best equipped to do, can be much more satisfying to women than simply a longer time span between intromission and ejaculation.


Hong acknowledges—with great humility and humor, in fact—that his ideas on the evolutionary origins of premature ejaculation in human males are highly speculative. And his ideas were critiqued soundly by University of Louisville psychologist Ray Bixler in his very good 1986 review of Hong's theory in The Journal of Sex Research. Among many faults that Bixler finds in Hong's "survival of the fastest" theory, the basic logic just doesn't mesh with the obvious female pursuit of sexual intercourse. In chimpanzees, for instance—a species for which male ejaculation latencies are measured in seconds, not minutes—it is often females that initiate mating behaviors. And then there's the "ouch" factor of having a sexually recalcitrant female partner whose dry genitals aren't terribly inviting. If Hong's model were correct, says Bixler:

There would be little or no proximal cause, other than coercion, for female cooperation-and it should be very clear that she would have to cooperate if voluntary mating were to be speedy! If she were not lubricated he would have "to rasp it in," a painful experience for the woman, and … "no pleasure" for him either.


Disappointingly, this is more or less where the evolutionary thinking stops. Apparently no other theorist—at least, no experimentally inclined evolutionary theorist—has picked up Hong's lead in trying to tease apart competing adaptationist arguments regarding male ejaculation latencies. Pieces of the puzzle are floating about out there, I suspect, such as the Finnish research showing that vaginal sex leads to faster ejaculations compared to other sexual behaviors; but Hong's article was before its time—premature itself, in light of today's more informed evolutionary biology, which is now poised to construct a more nuanced empirical model about this evolutionary legacy that is behind so many of us being fast finishers.


Another big piece of the puzzle can probably be traced to our species' specially evolved social cognitive abilities, which enabled us-possibly only tens of thousands of years ago, just a splinter of a splinter's time in the long course of our primate history—to experience empathy with our sexual partners during intercourse. A male concerned about bringing his female reproductive partner pleasure during sex, and thus deliberately prolonging the act of coitus to delay his own orgasm for her sake, couldn't possibly have been selected for in an ancestral species that more than likely saw others' bodies as pieces of mindless meat.

The subject may not appeal to everyone, of course, but given the unpleasant stigma attached to premature ejaculation, I really do believe that an evolutionary approach to the "problem" can greatly inform clinical treatments, a (not surprisingly) high-grossing therapeutic area of which there is no shortage of work being done. But in any event, Hong's seminal Reagan-era ideas should give us all pause in labeling any particular intravaginal ejaculation "premature"-Mother Nature, arguably the only lover that really matters, after all, may very well have had a thing for our one-minute ancestors.



Jesse Bering is the author of Why is the Penis Shaped Like That?: And Other Reflections on Being Human. A research psychologist and former director of The Institute of Cognition and Culture at Queen's University, Bering is a regular contributor to Scientific American, Slate, and Das Magazin (Switzerland). His writing has also been featured in many other sources, including New York Magazine, The Guardian, Discover, The New Republic, NPR, and the BBC. For more, visit his website, or follow him on Twitter.


This post originally appeared at Scientific American's Bering in Mind. It has been reprinted here with permission.