Ponderings on social analogy between baboons and the spotted hyena
(writing in progress)
Here are some new facts and realisations, based on Estes (1991), on the topic of facial expressions in baboons and Old World monkeys.
SMILING
It is easy to assume that only humans have the facial expression we call smiling.
However, cercopithecoid monkeys and anthropoid apes also smile, in a way. The expression is called not a smile but a ‘play face’.
The important aspect is that the configuration of the mouth is similar to that of the aggressive fang-baring expression, but the eyes look different. “The teeth are bared as in bared-teeth threat but there is an obvious difference in the eyes, which are often slitted or partially closed, never staring”.
Apart from the opening of the jaws, why could this not be called a ‘happy-grin’? I do not see the openness of the mouth as a disqualifying factor, because baboons also perform the fear-grimace, at least part of the time, with an open mouth.
Could it be that many of our relatives smile in a way that is both homologous and analogous to our human smile? I suspect that, if anyone has written anything erudite on this, it will be Desmond Morris.
DENTAL ADVERTISEMENT
I now realise that baboons have both visual and audial displays of their dangerous canines. They ‘fang-bare’ conspicuously by both yawning and the ‘canine threat display’. However, they also use what Estes (1991) describes as ‘tooth-grinding’.
I suspect that it is not the molars that are being grinded here, but the upper canines against the lower premolars that function as ‘whetting stones’. I.e. when a male baboon grinds its teeth, it is actually sharpening the canines, and the sound is warning the other by reminding it of the sharpness of the canines.
If there is any member of the Carnivora that has an audial display of the canines, it has slipped my mind. I suspect not. In this sense, primates out-canine the carnivores:
- their canines are in some species proportionately larger than those of carnivores;
- the canines remain sharp because they are whetted against a special lower premolar; and
- there is an audial as well as visual display of the canines.
Balancing this, though, is the fact that in most primates the female has far smaller canines than the male (I seem to recall this is not true for gibbons and I need to check which other species of monkeys and apes have impressive canines in the female).
Estes (1991) does not feature the gelada. However, photos on the web establish for certain that females of the gelada often use an expression which is either an assertive fang-baring, or a fear-grimace. I suspect that it is mainly a fear-grimace, although not usually described as such.
One of my reasons is that the canines, although discernible, are not large enough to be dangerous-looking in females of the gelada (please see photos below). If I am right, the main difference between the gelada and other cercopithecids is the lip-flip, performed in the fang-baring expressions (yawning, fear-grimace, canine threat in male, etc.).
PENIS DISPLAY
The accounts in Estes (1991) leave me in no doubt that, in not only baboons but Old World monkeys in general, the penis is used to display confidence, self-assertion, and status, way beyond any purely sexual communication.
For example, not only baboons but most cercopithecid monkeys have a display in which a mature male individual takes a sentinel role, guarding over the group, with his legs slightly spread and his penis partly erected, the conspicuousness of the penis accentuated in some species by bright hues.
It seems that the non-sexual display of the penis is quite different in Old World monkeys and baboons on the one hand, and the spotted hyena (Crocuta crocuta) on the other. In the former, the display of the penis is assertive, whereas in the latter the display of the penis is submissive/self-effacing. I have not found anything in the literature that actually states this basic difference. However, it seems obvious on reflection. If I am right, this puts a new complexion on the evolution of the peniform clitoris of Crocuta.
Coming back to the face:
One of the main differences between monkeys and the spotted hyena is that in the former the eyebrows and eyelids are used in various facial expressions, in combination with the mouth. Although the eyes are more expressive in hyenas than in felids, canids, viverrids, etc., the spotted hyena has no eyebrows and no display of eyelids.
The closest thing I have seen, in the spotted hyena, to the primate pattern is the complex wrinkling of the skin on the forehead, particularly right between the ears. This produces a quizzical look. However, I do not assume this to be a functional expression, because it is so subtle, and there is no accentuation of it by colouration, as far as I know.
I now see that the gelada and the spotted hyena both show the fear-grimace in extreme ways, by particularly stretched mouths. In the spotted hyena it is mainly the gape that stretches to the maximum in the fear-grimace, while in the gelada it is mainly the upper lip, which actually flips inside-out.
It remains to be seen whether the gelada ‘smiles’ (i.e. a happy expression) with the lip-flip, i.e. whether it possesses a positive version of the fear-grimace, that also shows the maximum exposure of the upper gums. If so, I doubt whether any primatologist has noticed it, for more or less the same reasons as the failure to notice the fear-grimace in the human species.
spotted hyena with gelada: not only do both species use extreme exposure of teeth and gums in some facial expressions, but it may also be true that both species have a ‘happy-grin’.
Theropithecus gelada female:
What is almost certainly a fear-grimace:
http://www.shahrogersphotography.com/gallery/Upload/SM08FR-520.jpg
In the spotted hyena there is a greeting ceremony, in which one individual sniffs the erected phallus of the other at some length. We have noticed that this takes trust, because of the vulnerability of the phallus should manners break down in an animal with such dangerous dentition.
We have also noted the similarity in complex social structure between the spotted hyena and baboons – something well-recognised in the literature.
Today I discovered a deeper level of analogy here: in baboons there is likewise a kind of genital greeting (among males) which signifies trust and reinforces the social order.
I have before me pp. 191-193 in Frans de Waal’s (1996) ‘Good natured: the origins of right and wrong in humans and other animals’.
I quote from a section devoted to discussing the difference between coercion and persuasion.
“Perhaps the best-known form of negotiation among primates is the way adult male [anubis] baboons greet other males in their troop...one male will typically walk up to another with a rapid, swinging gait. He looks the other straight in the eye with some friendly expression, such as lipsmacking, which makes it absolutely clear that he only wants to initiate a greeting...The encounter...follows a certain protocol that varies with the kind of relationship the two males have. Often, the other welcomes the approach with a similar friendly expression, and one male presents his rear end while the other touches or grasps his hips. They may then proceed to mounting, or, if they really get intimate, one male may fondle the other’s scrotum or pull at his penis. Known as ‘diddling,’ it is a sign of tremendous trust. The contact lasts only a few seconds, after which the two males separate again. Male baboons do not seem comfortable enough in each other’s presence to associate or groom; their predominant modes of interaction are fighting and greeting. The same behavior was studied...in a large colony at the Madrid Zoo...found the encounters to be extremely tense, occasionally erupting into fights. The reason is that they often serve to test and confirm who is on top, hence the jockeying for position to decide which male is going to be the mounter (generally the dominant) and which the mountee. Greetings thus seem a way of assessing intention: a male who used to elicit presentation in another learns from his partner’s refusal that their previous roles are no longer working, and that a serious challenge may be in the air. Since tensions remain under control in the vast majority of greetings, the advantage of this sort of information exchange is that matters can often be worked out without physical confrontation...A few combinations of older males have...reached the point at which dominance hardly matters anymore; they have moved from asymmetrical to symmetrical greetings...two devoted allies [Boz and Alexander]...every day, first thing in the morning, the two males would go through a series of intimate greetings so carefully balanced that one would think they were keeping count. Boz would present to Alexander to let him touch his genitals, while both gazed into the other’s face and lipsmacked. Two minutes later Alexander would present to Boz for the reverse procedure...The formalization of roles and the remarkable involvement of vulnerable body parts made Smuts and Watanabe draw a parallel with biblical oaths in which one man places a hand under another’s loins. Considering that the words ‘testify’, ‘testimony’, and ‘testicle’ share a common Latin root, it does not seem too far-fetched for these primatologists to speculate that ‘the genital touching that sometimes occurs in greetings perhaps serves to enhance the truth value of whatever these males are ‘saying’ to each other within the formally circumscribed context of greeting. Lacking articulate speech, and unable to swear oaths, perhaps male baboons make a gestural equivalent by literally placing their future reproductive success in the trust of another male. Such risky gestures may help to enhance whatever verity is presumed in the greeting because they impose a potential cost on the presenting male.’”
In the spotted hyena it is females that are dominant, but the principles seem similar. One individual is ‘under oath’ to another as signified by the presentation of the vulnerable genitals as ‘collateral’ as it were. It is easy to see how this mortgage promotes honesty as opposed to deception, not so?
I note again that there is much more going on here than mere submission; in baboons as in the spotted hyena my interpretation is that there is a demotion/humiliation for the inferior partner. In male baboons, the reproductive future of the individual is placed at stake in the ‘oathing’ or ‘mortgage’.
If there is a similar ‘mortgage’ in females of the spotted hyena, do you see that it would take more than just the normal female genitalia to make this oath credible? This is because the vulva is not crucial and vulnerable in the same way as the testes are. The testes are so precious for producing sperm that they should actually be protected deep in the body in terms of security; the fact that for whatever physiological reason they are on the outside means that for males to ‘swear on oath’ their hierarchical agreement has real credibility – because the implication is ‘if I cheat this hierarchical agreement, you have the right to destroy my testes next time we greet’.
So this obviously leads to the crucial question ‘how can females make an analogous oath as credible, in a female-dominated society?’ The answer is to evolve a genital anatomy in which there is indeed some external organ that is crucial to reproductive success.
Hence, I argue, the fact that the clitoris of the spotted hyena is not only prominent but also the birth-canal.
By converting the clitoris into the birth-canal, the spotted hyena is producing the hyenid equivalent of the exterior wearing of the testes. This is because the clitoris can kill the animal if it is infected under stress, and such infection can possibly spread to the whole genital tract including uterus and even possibly ovaries.
Furthermore, in mature females that have already passed that test, infection of the clitoris continues to be risky because of how close the clitoris is to the udder. Infection of the udder would certainly detract from reproductive success. If it is true that there is an ‘immunity-proving’ involved in birth through an inevitably ruptured bottleneck, can readers see that having the same organ bitten by another would also risk lethal infection? (this seems simply consistent in terms of this rationale).
In considering that the bottlenecked birth-canal of the spotted hyena is the vulnerable equivalent of testes in terms of providing credible collateral for social oaths, it is interesting to consider the reasons for the mimicry by females of the spotted hyena of the scrotum. Although I do not think the peniform clitoris shows sexual mimicry, it is hard to argue against sexual mimicry in the case of the pseudo-scrotum of females of the spotted hyena.
It is almost as if this species is saying with its anatomy: "I’m female but I’ve got balls, and these balls are on the line if I cheat our agreement." Because the animal cannot place its ovaries in its pseudo-scrotum, it does the next best thing: it places, close to the ‘false balls’, a structure that does much the same thing: risk damage that reduces future reproductive success, whether via the birth process or via the lactation process.
Based on the above thoughts, I can add something conceptually to the idea of immunity-testing, as follows:
It is not just at first birth that the immunity of females of the spotted hyena is being tested by the anatomical peculiarity of the peniform clitoris. Even after the individual has passed this first and most painful test, she continues to be tested because any injury to the clitoris risks infecting the UDDER. It is no accident that the clitoris is so close to the udder that it almost looks like an extra teat. Why is there this proximity? The answer may be: infection of a wounded clitoris means infection of the udder. Since the udder is as crucial to the niche of the spotted hyena as its unique premolars, this is significant.
An immunity-based interpretation: it is not just first birth, it is throughout the life of individual females that changes in rank can occur owing to performance of the immune system just after birth, when even just stretching, stressing and slight injury of the mature clitoris could infect the udder. Furthermore, the same anatomical arrangement also provides the credibility needed in social oaths during the greeting ceremony.
This approaches a rationale to explain why the clitoris of the spotted hyena is BOTH a particularly vulnerable example of genitalia AND the birth-canal. (To refresh reasers' memory of the conceptual puzzle here, it would have been strange enough for the spotted hyena to have the most penis-like clitoris on Earth, without this also containing the birth-canal; so there is a double-puzzle here, which the literature on this species is not clear enough in stating.)
A question of the use of English: I feel that part of the reason why no student of the spotted hyena has previously solved this problem is poor definition of words and poor description of the structures involved. What about ‘mortgage’, a word perhaps not previously suggested in explanation of the peculiar anatomy of the spotted hyena.
This word seems apt because its derivation is from the root for death (mort, as in mortuary or mortality) and gage, which means pledge/commit (same root as in ‘engage’). So, a mortgage is a ‘pledge/commitment on pain of death’ as it were. I am coming to see that this is what the peniform clitoris of the spotted hyena, which is really a bottleneck birth canal plus immunity-test teat, really is: it mortgages the animal for purposes of social status, the social status being crucial for reproductive success.
In the following, the expression seems more confident and assertive based on eyebrow display plus solidarity, but the mouth posture seems indentical to fear-grimace:
https://yooniqimages.blob.core.windows.net/yooniqimages-data-storage-resizedimagefilerepository/Detail/10531/8b063afa-029b-48de-9e9b-1308696d4824/YooniqImages_105314822.jpg
(writing in progress)
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