There are so, so, many areas in which the idea of intelligent design falls flat on its face or, because of the nature of this writing, get a kick in the balls. Surely, none more so, that the evidence in the placement of men’s testicles. Why on earth would anybody, intelligent or not, place a man’s testicles in such a precarious place? Why when, with just the simplest of taps, a man can be brought to his knees and end up curled up in a ball on the floor crying his eyes out, would any god allow any of its beings to suffer such a cruel and humiliating fate. I can only imagine that “Everyone will come and kneel before me” was probably originally succeeded by “or a swift kick in the nuts will have you on BOTH knees!”
Alas, the truth behind the positioning of the testicles is far less comical than the effect of being kicked in them but is actually far more interesting and a fantastic argument for evolutionary biology and a great way to get everyone’s attention in class. Ignore the giggling, or maybe even play on it for engagement; this is a fascinating way to get students hooked on both biology and evolution.
Ask the question to most adults and high school students, “why are the testicles on the outside of the body?” and you’ll probably get a similar answer from some or most of them; that for optimal sperm production, testicles need to be a few degrees lower than the body’s mean temperature. This will be a great answer, and partly correct. It also shows an intrinsic understanding, although maybe not readily apparent to most, that the body is not of an ideal design. If you were to ask the follow-up question of, “then why do you think that our entire body temperature isn’t a couple of degrees cooler so that testicles could be on the inside?”, then you’ll probably stump most people.
The full answer and explanation go back a long, long way in our evolutionary history, back to when we used to be cold-blooded fish. The testicles, or gonads, even back then still needed to be kept at the optimal temperature for sperm production. The perfect place for these was in the chest cavity close of the heart and liver which was the warmest part of the body; in most fish and sharks today, they still are. As evolution progressed and we became warm-blooded, the testicles needed to find a cooler place, due to the increase in our new core body temperature. The penis also travelled a bit further south but didn’t have as far to travel as the testicles; this evolutionary step of the movement of the two parts is also evidenced by the vans defrens, but a little more on that in a moment. In their journey to find a cooler place, the testicles eventually had to break through the body wall in the region behind the navel so that they could continue their journey. When they finally got to the right spot, the skin around them formed the scrotum that has its own network of muscles that contract and relax to move the testicles closer or further away from the body as needed according to the surrounding temperature. Any male who has ever ventured into the sea off the coast of Scotland will know the effect that I’m talking about, as will anyone else was taken a cold shower, looked down and wondered where everything has gone.
An intelligent designer would, surely, have even made it possible for our bodies to operate at a slightly lower temperature so that sperm production was not impeded or would have, at least, made the issue of sperm production not so temperature-dependent. That brings us back to the vans defrens which is our other piece of evidence that our reproductive organs have moved over time. The vans defrens is long, far longer than it needs to be when you consider the short distance from the testicles that the penis. If you follow the premise that a short route is a quick route, then you’ll be forgiven for wondering why sperm travels the route and the distance that it does. The answer, again, lies in our evolution and the route that our testicles have travelled from our chest cavities to their present position.
Evolution does not make giant steps or leaps but makes changes a little bit at a time. The vans defrens, the tube that carries the sperm from the testicles to the tip of the penis first travels back up the body, passes in front of the pelvic bone (through the weak spot that has been created in the body wall that I mentioned earlier behind the navel area), loops over the pelvis and up over the bladder, travels towards the back of the body around the back of the bladder, travels back down again around the rear side of the bladder where it joins the Seminal Vesicle where sperm mixes with seminal fluid. From here, it joins the urethra and continues travelling back down where it enters the penis. That certainly is some trip for the sperm to make from the testicles to the penis, but if you look at a cross-sectional diagram of the male reproductive system, it is extremely easy to imagine where the testicles used to be. The length of the vans defrens makes it easy to imagine that you could, quite simply, move the testicles further up the diagram and their position would fall in the chest cavity close to the heart and liver where they originally were in our cold-blooded ancestors.
As always, science and fact trump ‘intelligent’ design every single time. You only need to look at the human embryo and foetus as they are growing and developing to see the route of the gonads. In the early human embryo, the gonads still start out in the chest region and travel down to their intended destination during pregnancy. Female gonads will travel to the abdominal region, and form ovaries; male gonads will continue down, through the weak spot in the body wall and eventually form the testes.
Incidentally, this weakness in the body wall that has been formed over time to let the testes through is the reason why many men are prone to inguinal hernias; which occur when tissue, such as part of the intestine, protrudes through the weak spot. Evolution does this every now and again when it decides to make an adaptation; there is quite often a vulnerability or a downside as a consequence of the change. Potential hernias caused by the weak spot in the body wall that is formed to allow the testes to descend, or, more dramatic and devastating such as the extinction of the very species that has adapted. For example, the dodo or the kakapo parrot. Both birds lost the need to fly over time as they had no natural predators in Mauritius and New Zealand respectively. The birds became walkers instead and built their nests on the ground. It was only after the introduction of humans to both countries, and the arrival of rats, cats, dogs, etc., that the dodo and kakapo finally had predators that decimated their numbers. The dodo is now entirely extinct, and the kakapo in New Zealand was thought to be extinct in the 1970s. They are still considered to be critically endangered, and it is only through the eradication of rats and other introduced predators and the careful conservation and the relocation of some birds, that numbers are slowly climbing again. Even so, there are still less than 200 kakapo parrots left in the world.