Myths About Balls: Why They Dangle, Why They HurtS

Jesse Bering, he of the hilarious penis column fame, is at it again. This time, we learn everything we ever (or perhaps never) wanted to know about testicles.

Reading Bering's article feels a bit like watching monkeys masturbate at the zoo: you want to look away, but there is something grossly fascinating about the single-mindedness with which they play with themselves. It also brings me back to the first time I discovered balls, complete with the whole huh, those reaction. After years of hearing about how important they are - including many "you have no idea how much this hurts!" moments - the actual thing was, to be blunt, a little underwhelming. Bering even notes that, in contrast to the much-idolized penis, balls are sort of the ugly little brother. But still, he is fascinated with them. And, it seems, for good enough reason: unlike the penis, balls are complicated.

Drawing from an article published in this month's issue of Evolutionary Psychology, Bering answers many of his own questions about human testicles. First of all, why are balls so dangly? Apparently, it's not because women like it, although the authors of the recent testicle study do consider this idea:

Gallup and his coauthors jog through several possible theories of our species' testicular evolution by descent. One of the more fanciful accounts—and one ultimately discarded by the authors—is that scrotal testicles evolved in the same spirit as peacock feathers. That is to say, given the enormous disadvantage of having your entire genetic potential contained in a thin satchel of unprotected, delicate flesh and swinging several millimeters away from the rest of your body, perhaps scrotal testicles evolved as a sort of ornamental display communicating the genetic quality of the male... Although descended scrotal testicles do satisfy the obvious criterion of being counterintuitively costly, the authors conclude that handicapping is an unlikely explanation. If it were true, we would expect to see scrotal testicles becoming increasingly elaborate and dangly over the course of evolution, not to mention women should display a preference for males toting around the most ostentatious scrotal baggage.

Having settled that, we learn that the key to understanding balls lies in getting a grip on the "activation hypothesis." Bering describes the theory of descended testicles serving as a "cold storage" for sperm, which keep best at lower temperatures. The "activation" part occurs when heat from the vagina (or we suppose, any kind of body heat) fires up the sperm, getting it ready to make the mad dash toward reproduction. However, this is not the only time when the cremasteric muscle is active. The cremasteric muscle, for those of you unfamiliar with Matthew Barney, is the thing that draws the balls up and down, thus regulating their temperature through proximity to the body. Or, as Bering describes it:

Fortunately, human scrota don't just hang there holding our testicles and brewing our sperm, they also "actively" employ some interesting thermoregulatory tactics to protect and promote males' genetic interests. I place "actively" in scare quotes, of course, because although it would be rather odd to ascribe consciousness to human scrota, testicles do respond unintentionally to the reflexive actions of the cremasteric muscle. This muscle serves to retract the testicles so they are drawn up closer to the body when it gets too cold—just think cold shower—and also to relax them when it gets too hot. This up-and-down action happens on a moment-to-moment basis, thus male bodies continually optimize the gonadal climate for spermatogenesis and sperm storage. It's also why it's generally inadvisable for men to wear tight-fitting jeans or especially snug "tighty whities"—under these restrictive conditions the testicles are shoved up against the body and artificially warmed so that the cremasteric muscle cannot do its job properly. Another reason not to wear these things is that it's no longer 1988.

Aside from the fashion advice, I think the most important thing we should take away from this is that while balls may not be conscious, they are very smart. They're so smart that they work independently:

In fact, the temperature regulating function governed by the cremasteric muscle can account even for the most lopsided, one-testicle-above-the-other, waffling asymmetries in testes positioning. According to a 2008 report in Medical Hypotheses by anatomist Stany Lobo from the Saba University School of Medicine, Netherlands Antilles, each testicle continuously migrates in its own orbit as a way of maximizing the available scrotal surface area that is subjected to heat dissipation and cooling. Like ambient heat generated by individual solar panels, when it comes to spermatic temperatures, the whole is greater than the sum of its parts. With a keen enough eye, presumably one could master the art of " reading" testicle alignment, using the scrotum as a makeshift room thermometer. But that's just me speculating.

The activation hypothesis also explains some other ball-related mysteries, like why we enjoy having sex at night. Again, this has to do with temperature. The cooler air at night make it easier for men to maintain "optimal testicular adjustments." Plus, since women tend to pass out after late-night sex, and thus remain stationary, the recently released semen have better chances of reaching their goal.

Finally, we get to the issue of pain. Why does getting kicked in the balls hurt so much more than, say, getting kicked in the shins?

If you're male, the reason that you probably wince when you hear the word "squash" or "rupture" paired with "testicle" but not with, say, "arm" or "spleen" is because testicles are disproportionately more vital to your reproductive success than these other body parts are. I, for one, had to pause to cover myself just by typing those former words together. It's not that those other body parts aren't adaptively important, but variation in pain sensitivity across different bodily regions, according to this view, reflects the vulnerability and importance different adaptations play in your reproductive success. Male ancestors who learned to protect their gonads would have left more descendants—and pain is a pretty good motivator for promoting preemptive defensive action. Or, to think about it another way, any male in the ancestral past that was oblivious to or, gulp, enjoyed testicular insult would have been quickly weeded out of the gene pool.

Interestingly, the cremasteric muscle also plays a part here. When the balls are threatened by a nearby stimuli (a pinprick to the thigh, for example) they are pulled up towards the body. This protective feature also kicks into play during sex, in order to shield them from "possible damage to too-loose testicles resulting from vigorous thrusting during intercourse." Huh. Well that doesn't sound at all pleasant, but there it is. And with that image, let's return to our regularly scheduled program of ball busting and vagina-centric news. At least until Bering publishes another article - maybe next time we'll learn all about the anus.

Why Do Human Testicles Hang Like That? [Scientific American]

Related: Science Scribe Writes Masturbatory Missive About Human Penises