Friday Weird Science: Do Your Balls Hang Low?

Mar 05 2010 Published by under Friday Weird Science

Sci came across this abstract via NCBI ROFL, the aggregation site with some truly hilarious studies on it, many of them worthy Friday Weird Science materials. And of course this one is EXTRA worthy. It's from the Journal of Medical Hypotheses. Wither Weird Science, Medical Hypotheses, but for thee?
So, coming up into this next week, Sci is proud to announce an awesome series of guest posts. Seeing as we spent the last three weeks or so on female reproduction, it seems only fair to represent the other side of the coin, and so, for this next week, we'll be covering the basics of male reproduction, courtesy of the awesome and brilliant Ambivalent Academic.
And what a way to get into it... Kumar and Kumara. "Swinging high and low: Why do the testes hang at different levels? A theory on surface area and thermoregulation" Medical Hypotheses, 2008.

As I'm sure many of you are aware, most guys have two testicles. In fact, almost ALL guys have two testicles. The testicles are up in the abdominal cavity as a fetus, and descend to hang below the abdominal cavity after birth. In some men (I've heard as high as 10%, but until I have a ref for that it's just anecdotal) one testicle will not descend, and so some guys have what looks like just one, and I don't believe there's a negative effect on fertility there.
There are three possible positions for the testicles once descended: hanging equally, the right one hanging higher, or the left one hanging higher. It's common knowledge that a lot of guys have one testicle that hangs slightly lower than the other. Some say that this goes with handedness, and if you're right handed your right testicle will be higher, but I think that's pretty silly. Approximately 21% of men are thought to have the right testicle lower, 27% hang equally, and I suppose if you assume 10% only have one, that leaves 42% with the left testicle hanging lower (the first two numbers are from this pdf, which I think is hilarious and might have to be blogged).
So the question is: WHY do a lot of men's testicles hang unevenly? There have been lots of hypotheses proposed for this: differences in embryonic development, vascular differences, evolutionary differences. But these authors came up with a different hypothesis: temperature!
So what does temperature have to do with your balls? Well, as guys probably know from encounters with things like cold showers, testicles are very sensitive to temperature.

Your testicles are sensitive to temperature because sperm development requires a slightly lower temperature than the 98.6 degrees Fahrenheit in your body. Hence, the testicles are suspended below the abdominal cavity, in order to have the right temperature at which to make the little swimmers we all know and love.
As to why one testicle might hang lowER, the authors propose that it is yet again due to temperature. When the balls hang at the same height, they reason, the inside surfaces of them are pressed together, and this might mean that it's too hot in there. only the outside surfaces would be at the right temperature to produce sperm. Whereas, if one of the boys hangs lower, much more of that testicle would be exposed to the air, meaning it might have better temperature conditions in which to do its job.
Of course, this is a hypothesis. But there could be some cool ways to test this. I say, find guys with equal balls, and guys with one hanging lower, put them all in a room where the temp is equal and they have plenty of time to adjust to the room temperature. Measure the temperatures of each ball, and then check the viable sperm count of the dudes. If the lower hanging ball is indeed cooler, and those guys have higher sperm counts, you might be able to draw a correlation. Pretty easy to test, really. Additionally, you could get some data from guys going in for fertility treatment and low sperm counts. Do an overwhelming number of them have even hanging balls?
While Sci thinks that this hypothesis proposed above is not unlikely, and is something actually could probably be tested, she's not sure it's the right answer. My thought is that, if having testicles where one needs to hang lower confers a significant reproductive advantage (better sperm, obviously) when mating, then it doesn't explain the large number of men who apparently have equal hanging testicles. If the lower hang is important for increased function, those guys with equal hanging testicles would have been out-bred by now. So while I think the temperature hypothesis might be part of the reason, and might confer some advantage, I don't think it's the main reason.
Sci has...another hypothesis. Her hypothesis is space. This hypothesis actually might be good fodder for the Journal of Medical Hypotheses! (Who knows, perhaps Sci should publish there just for fun...) I am constantly hearing from various guys that their junk takes up space. Evidence of this can be found in the fact that guys always tend to sit like this on subways:

(Honestly guys, make some room! What do you have between there, the Eiffel tower?! Yeesh. I only wish I had Isis' skills with photoshop to make this photo that much more evocative...)
So yeah, dude's junk takes up space. They are constantly adjusting it, holding it up, pulling it around, etc. And it's true, between an average guy's legs there's really not a lot of space. Those balls are squished in there. So it is Sci's hypothesis that it's merely space that requires one ball to hang lower than the other, and that this is probably individual and not a genetically determined kind of thing (though who knows, really).
But of course, to get to the bottom of this, we have to do the experiment!!! Who's in?!
KUMAR, A. (2008). Swinging high and low: Why do the testes hang at different levels A theory on surface area and thermoregulation Medical Hypotheses, 70 (3), 698-698 DOI: 10.1016/j.mehy.2007.06.023

38 responses so far

  • Tony P says:

    Ok, I had to click this link because it was the strangest title I've ever seen on SciBlog. Yeah, my left nut hangs a little lower.
    Now the SO, my god. His hang about a third the way to his knees.

  • Fargo says:

    Yep, my own lefty hangs just a bit lower. Your space hypothesis seems likely to me, but not quite for the same reasoning. My testes can, and do, damned near fully retract into my body under certain circumstances, and with the slight offset the full width of both testicles doesn't have to get through there, in which case I imagine they'd simply remain more exposed.
    Perhaps ancestors that inherited this trait were somewhat less likely to suffer scrotal injury at the hands of violent persons places or things? Just enough of a pressure to make it prevalent without it being a requirement for propagation?
    I think it's also always important to consider that a trait is simply not inconvenient enough to be weeded out. Like buck teeth or blonde hair.
    Also, we sit like that because, as you should be able to guess, it provides some welcome airflow and easy hand access to The Region.

  • Jared says:

    Actually, in an A&P class I took, I learned a few neat little tidbits:
    When it gets warmer, the separation between the two testicles increases, lending support to the temperature hypothesis.
    If one's legs are closer together, however, the distance increases more, lending support to the space hypothesis-if this were only the case in humans.
    Many male mammals, however, have the same thermoregulatory scrotum, and on all of the ones I am familiar with, space is certainly not an issue. If anyone cares to analyze quadrupedal placental mammals with a scrotum to see if one hangs lower than the others. Such an observation would disprove the space hypothesis. If, however, they are found to hang evenly, it would disprove the temperature hypothesis.

  • You say that most men...but, most men each have more than the average number of testicles. Think about it.

  • Ian Tindale says:

    But hang on, this is just bollocks. They’re always on the move. Over a span of time, one is slowly creeping up, the other slowly but not necessarily in sync, creeping a bit further down, like a lava lamp or a background effect from the seminal ‘60's film “Barbarella”. It more or less comes down to when exactly you sample the position. I wouldn’t consider it true to claim that there are men who have equally hanging balls all the time — even those will make minor traversal journeys up and down a bit, independently.

  • Andy says:

    And here I thought it was perhaps more like breasts--you're unlikely to find a woman with a set that are perfectly symmetrical and even, simply because nature isn't carrying around a level making sure everything's plumb.

  • IanH says:

    I seem to remember reading that for most men, it's the left which hangs lower. In fact a study into historical representations of this got an igNobel a while back:
    From a quick scan of the article, it suggests handedness may be involved, although I'm not sure how. Presumably as they descend during childhood there is some variation in how low they get, and the left and right may not descend equally. Maybe men being imbalanced may be a result of this. Anybody with specific paediatrics anatomy knowledge shed some light on this?

  • IanW says:

    It's definitely time to change your blogging handle to Sciperverse...!

  • F says:

    So, Ian @ 5, what you are saying is that there is something like indeterminacy in the testicular field, and that we should only be speaking of the probability of finding testicles in certain locations. (I certainly hope the probability density is entirely confined to the scrotum. I wouldn't like to find out what it is like to suddenly experience on testicle being across the room or somewhere in Denmark momentarily.)

  • F says:

    IanH @ 7
    It indeed would be odd to find that handedness is somehow correlated to hangedness.

  • Ian Tindale says:

    Additionally, you (well, I) can make them move further up or down a bit if you concentrate on them — not by muscular “hoisting” but more through focusing relaxation at them and giving them ages to decide to respond. But my findings this morning result in the conclusion that my left one can go lower or higher than my right one, which was defaulting to a lower position before I started. Maybe they do have “resting positions” but there’s a lot of other factors that could be affecting their instantaneous positioning at any given window of observation.

  • Daneel says:

    My question was always why should we expect to have both testes at the same hight? I mean, we are not perfectly symmetrical so it's only reasonable to assume that SOME guys will have their testicles hanging at different highs.
    That said, my fiancée often makes fun of my uneven balls.

  • LGRooney says:

    I blame pants! The way that pants are designed is such that the seam pushes up right into the middle of everything. The penis (if wearing boxers like I do) needs to fall somewhere and I happen to let it fall to the left. The left testicle hangs lower to get away from the extra heat (remember the best way to warm up someone who is suffering from hypothermia is skin to skin contact?). The right testicle is pushed up by the seam in the shorts and by the pants.
    Therefore, with their short-cut crotch design, modern pants suck! Much to my fashionista wife's disgust, I have trouble finding stylish pants, i.e., the crotch is cut too short and the seam pushes up so far that I am constantly having to adjust (beyond the fact that short crotches provide a bit too much exposure of the unruly design underneath the fabric).
    Any studies on whether aborigines who don't wear underwear or pants have the same hang imbalance? This might assist or shoot down my theory...

  • ObSciGuy says:

    Another (null?) hypothesis:
    Relative position doesn't matter at all (i.e. no significant ultimate/evolutionary cost or benefit), and it can all be well explained by the net forces created by the scrotum (which is capable of quite a range of shrinkage-here and stretching-there) and whatever other forces each testicle experiences. This includes forces on one another, their relative size/mass/density, and the rest of the plumbing inside the scrotum, etc.
    In any case, it seems an important baseline for any empirical study is to understand the basic (known) mechanics of testicle positioning. Then go and worry about whether or not relative positioning (in reality) deviates from what you'd expect, and if those deviations can be better explained by other mechanisms like simultaneous temperature regulation, compensation to avoid physical injury, etc.
    Hmmm... maybe someone should send this blog post to the Kinsey Institute? 😉

  • Peter says:

    I was born with both testicles undecended and it wasn't corrected until I was about 7 years old. Each one was done separately, about 6 months apart, but I don't like the way the surgeon positioned them. They don't hang low enough and are too close together. My right is slightly lower but they're still practically level. I definitely need more space down there.

  • chezjake says:

    LGRooney touched on one aspect of this, but it strikes me that some preliminary investigation as to any correlation of hangedness with wearing of boxers vs. tightey-whities would be desirable.

  • STM says:

    You mean some men actually have symmetrical balls? My right hangs like a full 2" lower than my left at most times -- what a mess! lol And like somebody said above, jeans aren't made for long hanging balls, so my junk is always balled up (pun intended) and hurtin'. Personally, I wish thems bastards had never even descended!

  • Cuttlefish says:

    A related line of scientific research, with TED talk, just for you, Sci:

  • thotso says:

    Testicles are less likely to get squeezed or banged against each other if they are hanging at different heights - for instance, while running. They take up less horizontal space when hanging one on top of the other. So, guys whose balls hang at the same height may be more susceptible to testicle injury, and therefore less likely to reproduce.

  • Chuck VA says:

    Your boys are hanging in a sack. Of course one hangs lower.
    Put two apples in a plastic grocery bag. What happens?

  • Chuck VA says:

    Oh, and another thing on the subject of balls.
    I sure wish Barack Obama would grow a pair.

  • Jared says:

    But Chuck, anatomically, they are in two separate sacks, and not held by the scrotal skin itself, but suspended by muscles from the body which are also (very loosely) attached to those same muscles, thus your analogy of apples in a bag is not accurate.

  • Alex says:

    Years ago, when I was in Peace Corps, my neighbor let me in on what the Paraguayan campesinos called the increasingly present Mormon missionaries:
    The testicles.
    They come in pairs, and one is always shorter than the other.

  • gwen says:

    Does anyone know if it is normal for my three year old grandson's testicles to hang so low that they look like they could belong to an 90 year old man?

  • oldfart says:

    At 65+ I have started to have an issue with this topic. Because of increased hanging I have had to start using the handicap stall, which has a higher seat - otherwise the twins are swimming the the toilet water. YUK

  • Rick says:

    I'm not an anatomy student but I do have my own theory. If testicles hung evenly as the acrylic balls of the "Clackers" did they would strike each other in a painful manner. Although I doubt they would make the same sound.

  • Quak says:

    So, the vascular theory, I shall elaborate on it!

    Some background. Arteries supply organs with nutrient and oxygen rich blood. Veins bring nutrient and oxygen depleted blood back to the heart.

    So the arteries that supply each ball take similar routes, but the veins that take blood away from each ball take different routes. (Right testicular vein directly drains into the IVC while the left testicular veins drains into the left renal vein before draining into the IVC.) Meaning there is a difference in the pressure of blood draining and potentially pooling in each ball. Which leads to the left side being more engorged with blood and hanging lower.

    Of course there are variations in anatomy with everyone, and I can't even begin to explain why evolution decided this is the way we are designed. Anyhow, anatomy can be fun sometimes.

  • ecstatist says:

    "The water was so cold that I had a bump on both sides of my neck." (Scuba divers' hackneyed remark.)

  • [...] on steroids, fully preventing the tendency of the scrotum to “hang low” (which it does for thermoregulatory purposes). They caused the testicular temperatures to approach the rectal temperatures, which is way hotter [...]

  • Andy says:

    Actually, the reason the testes don't hang evenly is due to "fluctuating asymetry" - a normal product of small random events in early development. Handedness is likely the result of FA as well, so there could indeed be a correlation.

  • Gesagin says:

    Testicles don't hang at the same height as the other one for ease of movement while walking etc. If both were at the same height we would all be singing soprano.

  • foot fetish says:

    Asking questions are in fact good thing if you are not understanding anything
    completely, however this post gives fastidious understanding yet.

  • Alan says:

    I thought the answer was simple. When sitting down with legs together both testicles are in front. A right handed man more frequently crosses his leg right over left. So the right testicle ends up slightly in front and on top of the left. To make room in this small space the left one ends up sliding down between the legs. Do this enough, and the body accommodates.

  • Manuel Soliz says:

    I'm in !!

  • sky says:

    My left ball is way lower than my right one. I figured everything was okay and I'm sure it is. . if you asked me I would think that the balls hang lower than the other might have something to do with the structure of the individuals veins and blood vessels..

  • Andrew B says:

    Perhaps the thermoregulatory response as space hypotheses are both correct but not properly intertwined, what if it has more to do with which testicle the blood traveling downstate from the upper vesicle complex, including the brain, is arrived at first or more predominantly. Like a previous post stated, nature is not as consumed with balance and symmetry as we humans like to think we should. If one analyzes the various circulatory systems of a sample of any group of members of a given species they vary, not just in uniform size but comparative size within the given individual, so one testicle may simply have a wider inductive artery and therefore must hang lower to facilitate a faster egress of blood and keep the overall temperature more even, while the other testicle in men with one low hanging testicle may have a slightly constricted artery in relative comparison to the less descended testicle. Seems pretty simple if one understands hydro and thermal dynamics, wider 'piping' means freer flow of hottest blood and a shorter conduit reduces latency, while a lesser diameter calls for a longer circuit in order to preserve a needed delay for heat regulation. Seems like a rather lazy thesis, IMHO, or if written by a licensed professional seems to answer why malpractice insurance runs such high rates.

    Although a study could be performed as to the regularity of hang in conjunction to potential of severe congenital defects showing up later in life, i.e. when the relative amount of decent varies certain amounts or switches position entirely could it possibly indicate a heart issue in ones future. This makes sense as the tissue of the penis and smaller veins of the testes would be predisposed to heightened levels of plaque and cholesterol deposits in light of their proportionality of blood flow as compared to other sectors of the body, not to mention the fact that testerone and adrenal levels spiking during arousal and coitus would generate a certain amount of vaso-constrictive response, so being less than fit for the f***ing, could soon be an early indication of an up coming lack of being less than fit for the living. Not to mention early diagnostics of potential issues ones children may encounter health wise, after all if sperm grow in an environ rich of fatty tissue and other unintentional wastes deposited in the testicular complex isn't it likely that it could influence the resulting children's predisposition to heart conditions and/or other inherited diseases/complications?

  • Panda says:

    They're hanging that far below because your body temperature exceeds the temperatures your (balls) must be at. So they need to refresh a little bit and that's why they decide to hang below so that they can take some fresh air.

    see there as well

    Good luck.

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