A thought-stream on the genitalia of the spotted hyena
(writing in progress)
How peniform clitoris of spotted hyena could possibly be even more penis-like:
How could the peniform clitoris of the spotted hyena be more penis-like than it already is?
A related question is: given that the urinogenital passage runs through the peniform clitoris of the spotted hyena, does this add to its resemblance to a penis or detract from that resemblance?
My answer to the first question: well, the clitoris of the spotted hyena could perform some kind of ejaculation – which as far as I know it does not.
Female ejaculation is not some far-fetched or purely theoretical concept, because it certainly occurs in the human female. Given the unprecedented and bizarre conversion of the clitoris into a penis-like organ morphologically (but not so much functionally) in the spotted hyena, adding some kind of ejaculatory function would seem like a relatively easy task.
I can easily imagine such ejaculation functioning in e.g. scent-marking, instead of/in addition to the use of the anal glands (which are pretty bizarre themselves and the location of which near the anus is itself not easy to explain because they function quite separately from defecation). Or ejaculation could conceivably have been part of some sort of quasi-sexual behaviour among females in the spotted hyena, possibly combined with rape.
A truly peniform clitoris would, to my mind, perform ejaculation, but this has not evolved in the spotted hyena and so this detracts from the convergence with the penis, not so? This is not a pedantic or trivial matter, because it ties in with the surprising reality that the clitoris of the spotted hyena is in a sense functionally opposite to the penis, in that it is erected and displayed more as a sign of demotion than as a sign of promotion (e.g. libido or self-assertion).
Which leads to an original realisation: that one of the most interesting things about the spotted hyena is how lacking it is in ejaculatory function considering its otherwise close resemblance to the penis. (This is linked to the assumption that the peniform clitoris of the spotted hyena confers no sexual pleasure.)
My answer to the second question: well, the location of the urinogenital passage within the clitoris of the spotted hyena is neither here not there in any assessment of homology and analogy relative to the penis. This is because the penis does contain the urinogenital passage. but genitally this is used only for an outward flow of semen. Nothing enters the reproductive tract via this route.
If the clitoris of the spotted hyena were as it is, but the vaginal tract opened separately from it, would this clitoris be any less ‘monomorphic’ with the penis? I doubt it, because neither a vagina nor a birth-canal are intrinsic to a penis.
A most surprising thing about the spotted hyena is the fact that it gives birth through what looks like a penis. When one describes its clitoris as ‘peniform’, this is in a sense subjective and biased, because one is implicitly overlooking that there is nothing peniform about a birth-passage.
Putting these two insights together, and coming up with a new interpetation:
How could the peniform clitoris of the spotted hyena – which is probably the most penis-like clitoris in the whole animal world - be even more penis-like? Simply by
- passing ejaculate, and
- not passing newborns.
I.e. if this clitoris passed, from the body to the exterior, ejaculate rather than neonates, it would be even more penis-like than it is.
To take this logic to the formulation of a really deep and meaningful question about the spotted hyena: the fact that the clitoris of this species is so very penis-like, but does not ejaculate instead of giving birth, is a central puzzle for us to solve.
The main thought/idea emerging for me from this is that the penis-like shape presumably evolved simply to mimic the appearance (as opposed to function) of the penis. (The reason for this mimicry is of course still unclear.) If so, is it really surprising that the clitoris does not include ejaculation?
As I see it there are two problems with this.
Firstly, the similarity cannot really be described as mimicry although it can be described as resemblance. But resemblance to what end?
Secondly, the main function of the clitoris is to communicate via the olfactory sense. And for this it is hard to see that visual resemblance is essential for olfactory resemblance.
It is unsurprising that the clitoris does not perform ejaculation. However, regarding it as functionally similar to the penis (which is implicit in ‘mimicry’), or even calling it ‘penis-like’ or ‘peniform’, is subjective/biased if it does not do the most important things that a penis does.
I.e. what I am suggesting is that this clitoris is actually not similar to the penis in any meaningful sense. Focussing on its superficial similarities to the penis does not seem to have produced an understanding of the spotted hyena. It is just as rational to emphasise the differences, because both the similarities and the differences are valid.
Perhaps the differences will provide the insights that the similarities have so far not provided?
Further thoughts on idea that the clitoris of spotted hyena mimics the penis:
The essence of mimicry is communication, not resemblance. Mimicry is a false communication in which similarity falsely claims identity or at least analogy.
When someone claims that the clitoris of the spotted hyena mimics the penis, they are implicitly claiming that the clitoris is communicating a (false) resemblance to the penis. This sounds untrue, because
- the visual sense is minor to the olfactory sense in the spotted hyena, and
- the clitoris shares few functions with the penis.
The case for mimicry comes down to whether or not the form of the organ is essential for the scents it puts out. This is, of course, possible. It could be that the details such as a glans, a prepuce, and small spines, plus the flaccidity of the organ for most of the time, all act together to provide a ‘recipe’ for an olfactory brew that could not – or at least not easily – have been configured with a different size and shape.
That is possible, but it is not what is usually meant. The conventional view refers to the visual resemblance, which is misleading in my view.
There is a reasonable case that the clitoris of the spotted hyena mimics the penis olfactorily. However, this has not been stated clearly in the literature. Moreover, it is a hollow idea unless one can postulate why there would be an advantage to the female scents resembling those of the male.
I keep coming back to this: the clitoris is erected in a context OPPOSITE to that typical for the penis, i.e. in demotion/humility/self-effacement/lack of libido. So, even on an olfactory basis, the case for ‘mimicry’ seems questionable. If the female erected the clitoris to signify self-assertion/libido/sexual excitement/dominance/social superiority, then an argument could be made. But such is not the case.
So what remains of the notion that the clitoris ‘mimics’ the penis in the spotted hyena? (Also it’s worth bearing in mind that although the two organs are extremely similar when flaccid in juveniles, they are noticeably different (e.g. in the shape of the glans) when erect, and also any mature female shows tears/scars on the clitoris that do not resemble the penis.)
Hypothesis to explain bottleneck in birth canal of spotted hyena:
Considering the remarkable pathological immunity of the spotted hyena. This species does not suffer from the microbial afflictions that beset other, coexisting carnivores. Even rabies hardly affects it, although it carries the virus. It seems that the spotted hyena has specialised on an extremely powerful immune system, so that infection is, relatively speaking, the least of its worries.
But how does one interpret this w.r.t. the ordeal of self-imposed injury in first birth? Any other carnivore would risk lethal infection from the tearing of the clitoris during first parturition, but I suspect that the spotted hyena more or less laughs this off. If so, does this successful resistance to infection amount to passing a test, or is the species so immune that no real test is involved? This is a basic question of logic.
The penis generally seems designed in a way that invites infection, which is presumably why circumcision is so popular in the human species. The prepuce functions well, as long as it is kept fairly clean, something that tends to lapse when an individual is listless for whatever reason. So there is almost a sort of handicap built into even the human penis. I dare say a similar principle would apply to the penis and clitoris of the spotted hyena.
So when the clitoris is inevitably ripped for about 2 cm during first birth, this would seem to amount to a virtual invitation to infection. This is not only because any 2 cm lesion can easily get infected, but also because the clitoris is a potentially a particularly ‘dirty’ part of the anatomy unless the individual has the energy to keep it clean (e.g. by licking it, and even then I am unsure, because the bacteria in hyenas’ mouths must be formidable).
So perhaps the clitoris is a handicap w.r.t. immunity, and any individual that survives its first parturition along with its offspring has passed a significant test of immunity?
I offer the following as an original explanation for the evolution of a bottleneck in the birth canal of the spotted hyena.
The bottleneck is such a handicap that only the fittest female individuals can produce a surviving neonate, the less-fit individuals producing stillborn neonates.
There is no faking this test, so the handicap means something.
No other adult individual of the species witnesses, or participates in, birth, in the spotted hyena. The success or failure of the first birth is sure to be communicated in the ‘virtual’ system of the spotted hyena, i.e. by smell during subsequent greeting ceremonies with other female individuals. It should be extremely easy for one relatively young female individual to recognise whether a hierarchically comparable other female individual has given birth successfully on her first attempt, because
- the fact of first birth will be perfectly evident in the injury of the clitoris, and
- the successful first mother will be secreting milk.
These olfactory signals are so gross that they don’t even involve the more subtle scents of hormonal changes, which I am sure are detected in this species as well.
So we have a handicap, and we have a means of communicating the results of handicap. We also have a payoff for the handicap, because a successful first mother who rises a notch or two in the hierarchy is likely to enjoy improved reproductive success over her life.
This is more subtle and more self-imposed than infanticide in the lion. However, the fact remains that, in its own way, the spotted hyena commits infanticide when it attempts to give first birth through such a narrow bottleneck.
Such a system could evolve on the basis of buying a boost in status that cannot be faked. This is simply because the net benefit to reproductive success over the lifetime of all female individuals in the population outweighs the net detriment of a certain percentage being stillborn.
If I am right, one way of putting this is that the spotted hyena is so thoroughly selfish that it has even imposed its (ultimately beneficial) infanticide on itself. The selfish female produces her stillborn alone, with no chance of solace or help as seen in the human female with her also rather difficult childbirth.
And if she manages to produce a surviving infant then she enjoys the selfish gains commensurately. In a species that is so systematically selfish – in contrast to the extreme altruism of the African hunting dog for example – does it not make sense that even the handicap principle should be expressed in a selfish way?
Why is the birthing is an honest sign of fitness? Are we saying that a female has to be extremely fit to deliver the cub simply because she needs brute strength to push it through the canal i.e. this is all about measuring the physiological (e.g. ATP availability; successful immune system) and muscular strength of the animal? Are we hypothesising that an animal who is not completely on top of their game (in terms of immunity, physiology, strength, state of mind etc.) would not birth successfully? What factor is potentially most important for the hyena i.e. is there perhaps one fitness factor that the birthing process is a good proxy for?
My way of approaching an answer would be to apply the same question to the peacock’s tail and other prominent examples of the handicap principle. What exactly does a peacock’s tail prove?
The shape of the clitoris is still deeply puzzling. Why would an organ, used for testing fitness, resemble a penis? What possible advantage is there for females to resemble males in the spotted hyena? I doubt that there is any advantage. And the visual resemblance is not that close when the organ is erect (see the figures in the paper by Cunha et al.).
Females of the spotted hyena cannot be confused with males, at any age, if the erect glans is visible enough for the shape to be discerned: angular in males vs rounded in females. And when it comes to the clitoris smelling like a penis as opposed to looking like one, this rings true from the perspective that smell is such an important sense in the spotted hyena.
However, there seems to be little advantage in the female smelling like a male. It is easy to envisage a system of thorough dominance by females, in which the females smell like what they are: vicious, competitive, dominant, aggressive, and assertive. After all, the mammalian penis is not primarily an organ of communication via scent (although it does perform that function). Even if it is, the communication is usually more sexual than social.
(writing in progress)
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