When I walk my minature Dachshund (Dick), I can’t help but notice his poor little balls slam from side to side when he walks. It comes to mind that they’re sooo vulnerable hanging in the wind like that, as it is with most mammals. With most other critical body parts shielded by bone or muscle, why aren’t they? I posted this question some months ago and got a variety of answers that varied from temperature control to how nice they are to play with.I agree with both but never got an answer as to why so thought I’d try again. Any ideas?
I’m responding just because I think it’s ironic that you are asking a question about “something that hangs.” I guess your knowledge is limited to things hanging from two fixed points instead of one.
Lessee, the mutt is named “dick”, and you seem to observe his testicles a lot … have you seen a shrink about this?
As to the question - temperature control. A few mammals do have internal testicles, notably elephants and marine mammals like seals and whales. Some people have pointed to this as evidence of marine ancestry in the elephant, along with the claim that they used their trunks as snorkels:
Anyway, those animals with internal testicles have extra cooling adaptations to accomodate them.
Viable sperm can’t be over-heated. Hot tubs and tightie-whities are not good for baby-making. I won’t argue that those vulnerable, swinging-in-the-wind thingies aren’t important, but critical to sustaining life they are not. Then again, I’m a girl.
Temperature control is a consequence of them swinging in the wind. If they’d been designed into a proper, safe environment in the first place, they would have adapted to temperature changes in another way. As far as not being critical to sustaining life, I can’t think of many things more important. Maybe another way to ask is… Why do elephants and marine mammals have them safely tucked away until needed?
Keep in mind that while they may appear vulnerable to you, Catenary, as he trots along in front of you at the end of his leash, they are not vulnerable to other dogs he meets. I seriously doubt that Dick would turn his back to a potential aggressor. In a normal encounter, his whole body is between his jewels and the teeth of the potential agressor. Dogs don’t generally do the sniffing thing until they have decided they don’t want to rip each other to shreds. If one or the other growls, they will quickly be nose to nose again.
“With most other critical body parts shielded by bone or
muscle, why aren’t they?”
Ask the person who designed them. Otherwise we can only guess & several people gave excellent guesses to your inquiry before.
Also, human males sometimes have very low hanging balls. What would you guess that design is for?
Actually, what we’ve been saying is that temperature control is a REASON for dangling them in the breeze. If you just put them inside the body, and let them be the same temperature as the rest of your internal organs, the sperms get killed. Marine mammals and elephants have rather involved arrangements of blood vessels which allow that internal area to be cooled below ambient body temperature. There’s some name for the structure, which I don’t know off the top of my head. They presumably only evolved that when external ones wouldn’t work adequately with their lifestyle. In species for which the external testicles work, they’ll be retained, no matter that it seems like a dumb engineering decision. Evolution yields that kind of design. Marvin Minsky once had some very unkind things to say about the “wonder” of evolution on these very grounds. Face it, nature is a kludge. In a way, that’s what makes it interesting.
Women’s ovaries are deep inside. What a wonderful design concept.
Eggactly my point.
The “special” design of blood vessels in internal organs that need to be kept at non-body temperature is called a counter-current heat exchange system. Warm blood from arteries gets cooled by returning cooler blood in the veins, allowing different temperatures to be maintained in the body. Mammalian testicles are generally located outside the body because the ideal temperature for sperm production (in humans for example) is lower than body temp. For humans, sperm production is at about 35 C, while body temp is 37 C. The testicles can be moved closer to the body or further away in order to accomodate for environmental changes (ever notice how they “shrink” when it’s cold out?).
Also, interestingly, there is a counter-current heat exhange system in the placenta, since fetuses (?) temperature is about 0.5 C higher than that of the mother.
See, I DID learn something in Biology!!!
So how is it that the li’l swimmers can survive the journey to the ovum? IIRC from sex-ed they can survive for a couple of days in there. They are constantly being produced and reabsorbed in the testes on a roughly daily timescale, so I don’t see why body temperature should be such a problem.
I suppose the importance of the guys starting their journey cool and fresh might outweigh the vulnerability issue of external testes.
Maybe the balls hang low there so that men can do ‘teabagging?’ I don’t know if canines practice that idea though.
As mnemosyne points out, I should more properly have said that the higher internal body temperature would prevent sperms from being created in the first place. It still means you need some special arrangement for temperature control if you place them internally.