I have read in one or two serious (for laymen) books an evolutionary conundrum: that in almost all mammals (I forget the very few others), male humans have to “go through the trouble” of employing manifold brain and other obvious physical requirements to become erect to reproduce.
All other mammals simplify the physical part immensely by having bone-like penises that make their appearance when the rest of the organism is properly stimulated.
One suggestion for this evolutionary waste of resources is that the human male, by going through all this trouble, really is worthy of reproducing with by the very fact that he can get it up. But this still leaves the answer unsolved as to its uniqueness as an evolutioinary strategy.
The superorder to which humans and other primates, from apes to lemurs, belong, which also includes tree shrews and dermoptera (‘flying lemurs’) has as one of its distinguishing characters a pendulous penis in males. So that element is incorrect – a large group of mammals have pendulous (flaccid) penises that rise when erected. As for stimuli, a wide array of stimuli are known to be evolutionary strategies – consider the brightly colored bottoms of female baboons and drills in heat, pheronomic signals in numerous species, etc.
This doesn’t directly address your main point, but it seems to suggest that it’s founded on erroneous data.
A big point against this argument I see (biology layman) that the ability to get an erect penis and the ability to produce viable (“good for reproduction”) sperm IS NOT directly related, although for centuries of human history males have mistakenly assumed that as long as they were able to get it up, they could also father children (disregarding the evidence that if e.g. a male king has several wife, who have proven their fertility before/after with other men by bearing children, fails to produce offspring at all, obviously is not fertile. But because that would have impugned male image, it had to be the wife’s fault).
There are anecdotes of guys into high age who could not get an erect penis during normal orgasm, where the wife got pregnant by using the automatic morning stiffness, because the semen was still strong enough.
Fertility doctors will tell you when couples come to them unable to conceive, in one third the cases it’s the guy who doesn’t deliver, and in another third it’s both man and woman, yet the couple doesn’t know where the problem lies because the mechanics look fine.
The usual answer as to why humans have the unusual in animal kingdom year-long being in heat, or rather, falling in love, is that human children need a stable family unit, so evolution developed a love relationship to keep parents together to raise the children. Though that’s not so sure, either, looking at all the problems marriages have…
Sheesh, about my misinformation about other mammals exhibiting the characteristic. It always helps not to be a moron when presenting the “1000 Frenchman” factor.
Nonetheless, the question still stands. Why us and those guys? Or, as was mentioned above, that simply is an evolutionary definition of what “us” is… It does seem a waste of resources.
Unless there’s something weird going on in the background, the math on those fractions doesn’t work out. The probability of both the husband and the wife having reproductive problems that prevent conception should be significantly lower than the probability of just one of them having problems.
Of course, this isn’t a random sample, and human pairing isn’t random, either, but I strongly suspect that the 1/3, 1/3, 1/3 split you’ve suggested is not correct. Cite?
It is not necessarily that both are infertile, but that they are not fertile with each other. Reduced fertility in each mean that either could successfully become a parent with someone, but not with each other. (Mathematically, the reduction levels multiply; the idea, I think, is that when one is fertile the other is not, leading to failure of natural fertility. These are the people for whom IVF will work well.
I don’t know about that. True, a penis supported by bone is simpler and more reliable; but a penis bone requires calcium and the energy to form it into bone that a fleshy penis doesn’t.
Linguistics hijack: The penis bone is known as the os penis.Os means both a body opening and a bone in anatomy, both from Latin. The plural of the bone is ossa like osteoporosis, and the plural of the opening is ora like oral or orifice. /linguistics hijack
I don’t have a cite because I don’t remember where it’s from - either it was quoted here on the Dope, or I heard it from a friend who’s an anthropoly doctor and works with male fertility problems - , and it’s not a question of probability reported beforehand, but rather, a statistic reported from the fertility doctors after observing and testing their patients.
I would certainly not know how to calculate the probability of infertility, since there are many factors; some women who need treatment have their tubes cleaned by the doctors, and then things work, while some men have the problem that their sperm is not active enough to swim all the way. (I don’t know if they solve this with intra-tube-fertilisation, or collecting enough active sperm, or medication). On other threads, somebody mentioned that obese women will have problems conceiving because hormone activity will change; there’s been reports about male fertility decreasing in the last 60 years because of the rising amount of toxins and pseudo-female hormones in the enviroment (though other sources critic these reports as faulty).
Actually, when I read (heard?) this statistic I was very surprised, because I had expected a much more uneven distribution.
I think you just need to follow the thought through a little further. When does a man typically have problems getting an erection? The following cases make it more likely:
He is in poor health (including old age, poor diet, diabetes, hypertension and other factors)… suggesting he is either naturally unhealthy or at least not in a good position to help raise a kid
He is under a lot of stress… and you don’t really want to procreate when stress is high.
He is not sexually interested in the female… possibly suggesting that she’s not the best candidate to be reproducing with.
I don’t know it as a fact, but I suspect that a flaccid penis is a lot harder to break/injure than one with a bone. That might be a factor.
You also have to remember that, from an evolutionary perspective, a trait doesn’t have to be an advantage per se… it might just be something that got put into place that is not a disadvantage. Kind of like having testicles outside our bodies.
I wonder about the evolutionary benefit of humping the female for several minutes or more before delivering the seed. Wouldn’t it be advantageous to shoot in the first five seconds? You could still have the pleasure orgasm later for the pair-bonding.
This is speculative, but the pendulous penis of primates could have something to do with the fact that the body is often held vertical as the animal clings to tree branches. Having a pendulous penis guarantees the the urine stream will be directed downwards regardless of the position of the body.
(However, it should be noted that most other primates besides humans have a penis bone, although it is reduced in the great apes.)
Whales mate front to front, and have a mobile penis that can move about to locate the vagina. This flexibility is necessary for animals that lack the kind of limbs that can hold a mating pair close together.
Offhand, I don’t know what factors might have been involved in other mammals.
Actually come to think of it this is a very interesting question. Why do we have the ability (and indeed preference) for long drawn out sex that we really enjoy when, in terms of functionality, a pretty much instantaneous orgasm for men would do the trick?
In a similar vein why isn’t it easier for women to have orgasms? If I understand it when a woman orgasms it causes her cervix to spasm and “suck up” the sperm that pools in her vagina so ideally you want her to have an orgasm as part of the reproductive process.
I’m now more than I was when I started writing this post - guess it’s just as well I’m gay.
I’d think that it’s because for humans the majority of sex is for the sake of relationships and pleasure. We even have a low fertility rate and a hidden fertile period for women; we have evolved for not only long, drawn out sex, but for having lots of sex when we aren’t even fertile. And another reason we have long drawn out sex is due to the exercise of self control, not to mention manual stimulation, toys, cunnilingus - all sorts of ways we’ve devised to get around the “built in” limits.
Sex is not just, or even mostly about reproduction for humans.
One possibility is that it acts as a selector for males who are more attentive to her desires, and therefore more likely to care for her in general. It also makes cheating more efficient as I understand; women are more likely to orgasm with a lover than a husband.
than I was when I started writing this post - guess it’s just as well I’m gay.