As a youth at boarding school a common greeting was “How are they hanging?”, to which the reply varied but was often uttered as “up and down, thanks”.  Unless the weather was very cold (and it was in Ballarat winters), or one was wearing budgie smugglers* (which was unusual, even in summer in Ballarat), then the answer was accurate.

Jesse Bering, who suggests that testicles are, arguably, the only male human body part less attractive than the penis, has written about the whys and wherefores of testicular suspension.  The reason many mammals have testes packed in scrotum, away from the body is for temperature control.  In humans sperm are comfortable at 34 degrees celsius, a full 3 degrees below body temperature.  When they (the sperm) are heated to 37 degrees they become very active, but can only survive in this hotter environment for one and a half hours to a maximum of 4 hours, ample time for the active sperm to negotiate the female reproductive tract.  So sperm are brewed and stored in the cooler scrotal sack awaiting the hyperactivity induced by heating them to body temperature.

The scrotum surface varies from relatively smooth skinned in warmer weather to a wrinkled prune-like surface in the cold.  But it is not just the skin variability that regulates temperature, the cremasteric muscle provides thermoregulation by altering the height at which ‘they hang’.  “This muscle serves to retract the testicles so they are drawn up closer to the body when it gets cold (think entering the southern oceans, cold showers) and also relax them when it gets too hot.  This up-and-down action happens on a moment-to-moment basis; thus male bodies continually optimise 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.”

The lopsidedness, one testicle above the other, is a result of the totally independent temperature regulation.  Bering goes on: “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” he allows.

“One of the things you may have noticed in your own genitalia,” Bering continues, “(O)r those of someone you’re especially close to is that in contrast to the slackened scrotal skin accompanying flaccid, non-aroused states, penile erections are usually accompanied by a telltale retraction of the testicles closer to the body.    . . . this is another smart scrotal adaptation.  Not only does the cremasteric reflex serve to raise testicular temperature, thus mobilising sperm for pending ejaculation into the vagina, but (added bonus) it also offers protection against possible damage to too loose testicles resulting from vigorous thrusting during intercourse.

The cremasteric muscle has another trick.  “It flexes in response to threatening stimuli, in effect pulling the testicles up closer to the body and out of harm’s way.  . .   .  .   There are a number of ways to test this at home if you’re so inclined.”

(Quotes from ‘How are they hanging?’ in “Why is the Penis Shaped Like That?” Jesse Bering, Corgi Books, London, 2013)

* Budgie smugglers – swimwear favoured by Australia’s Prime Minister – see picture right