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