back to bonobos – and sex
Canto: We’re reading Rebecca Wragg Sykes’ brilliant book, Kindred, an almost up-to-date account (published in 2020) of all the new discoveries about our close relatives the Neanderthals, and the speculations resulting from them. And of course we’re always alert to the slightest mention of bonobos in any works of anthropology…
Jacinta: Yes, we’ve been a bit timid about talking too much about bonobos and sex, but a few mentions in Kindred have emboldened us.
Canto: W’ve seen the odd photo or video of chimps or bonobos with erect penises, and it was a scary but also puzzling sight, but we’ve not really explored the difference between theirs and ours, so now is the time to do so. So here’s some interesting comments linking humans, Neanderthals and our chimp/bonobo rellies:
Anatomically, pelvic dimensions point to vaginas very similar to ours, and as penises are tailored to fit, those too were probably more like living men’s equipment than that of chimpanzees.
Luckily for all concerned, unlike chimps Neanderthal males lacked the genes for ‘penis spines’. While in apes they’re more like tiny hardened pebbles than spikes, their presence does affect copulation: marmosets have sex and orgasms that last twice as long when the spines are removed.
We should probably therefore picture Neanderthal sex as more leisurely and satisfying than chimp-style rapid thrusting bouts. Not forgetting clitorises – organs solely existing for pleasure – unluckily for Neanderthals, like us they probably lacked bonobo-like versions that make face-to-face orgasms easier. But masturbation in some form is pretty much guaranteed, whether during sexual encounters as is found among humans, or more generally for social bonding and diffusing tensions, as in bonobos where it takes place between pretty much anyone.
Kindred, Rebecca Wragg Sykes, p 271
Jacinta: So this makes me want to know more about the bonobo penis, and ‘penis spines’. It sounds like it isn’t ‘made for pleasure’, which helps to explain why female-female sex is the most practised type among bonobos.
Canto: Then again chimps have the same penises as bonobos but they’ve evolved differently. So here we go with ‘penile spines’. First, Wikipedia:
Many mammalian species have developed keratinized penile spines along the glans and/or shaft, which may be involved in sexual selection. These spines have been described as being simple, single-pointed structures (macaques) or complex with two or three points per spine (strepsirrhines). Penile spine morphology may be related to mating system.
This is news to me, but fascinating.
Jacinta: Just up our alley, so to speak. So to elaborate on this last quote, again using Wikipedia (largely), strepsirrhines are a suborder of primates including lemurs, galagos or bushbabies, pottos and lorises. Sexual selection is, I presume, a form of mating system, which Darwin reflected upon in The Descent of Man, inter alia. Macaques are a type of Old World monkey, with 23 known species. Interestingly, they’re matriarchal and frugivorous, like bonobos.
Canto: Apparently they’re a feature of felines – penile spines, that is. In cats, it’s speculated that they may contribute to pregnancy, as they ‘rake the walls of the female’s vagina [during withdrawal], which may serve as a trigger for ovulation’. I’m wondering, though, how that might relate to sexual selection. ‘A spiny dick, nothing turns me on more.’
Jacinta:
It all works below the conscious level, mate. I mean, female bowerbirds hang out with the males with the best display, but I don’t think they’re thinking about sex, especially considering how much of a nothing bird sex generally is. But getting back to bonobos, Wragg refers in the above quote to ‘bonobo-like’ clitorises that make face-to-face orgasms easier than it was for Neanderthals and, more to the point, we H sapiens. How could we have missed this in all our explorations of the bonobo world?
Canto: Hmmm. I blame the prudery of researchers. Including ourselves. Anyway, it probably all gets back to genes and their expression. So we need to explore – but should we look at penises first or clitorises – is that the plural?
Jacinta: Not sure, I can only cope with one at a time. So here’s something we should never have missed:
Bonobo clitorises are larger and more externalized than in most mammals; while the weight of a young adolescent female bonobo “is maybe half” that of a human teenager, she has a clitoris that is “three times bigger than the human equivalent, and visible enough to waggle unmistakably as she walks”. In scientific literature, the female–female behavior of bonobos pressing genitals together is often referred to as genito-genital (GG) rubbing. This sexual activity happens within the immediate female bonobo community and sometimes outside of it. Ethologist Jonathan Balcombe stated that female bonobos rub their clitorises together rapidly for ten to twenty seconds, and this behavior, “which may be repeated in rapid succession, is usually accompanied by grinding, shrieking, and clitoral engorgement”; he added that it is estimated that they engage in this practice “about once every two hours” on average. As bonobos occasionally copulate face-to-face, evolutionary biologist Marlene Zuk has suggested that the position of the clitoris in bonobos and some other primates has evolved to maximize stimulation during sexual intercourse. The position of the clitoris may alternatively permit GG-rubbings, which has been hypothesized to function as a means for female bonobos to evaluate their intrasocial relationships.
Canto: What can I say?
Jacinta: So this quote, from Wikipedia, compares the bonobo clit to the human one, but says nothing about chimps. I mean, it occurs to me that this enlarged clit, and the pleasure derived from it, would help to explain female-female sexual bonding, leading to social bonding, leading perhaps to matriarchy, if we can call it that. But if chimps have the same-size female pleasure-place, that thesis collapses.
Canto: Good point. So, googling ‘chimp clitoris’ takes me first to an essay from nearly 40 years ago on ‘The external genitalia of female pygmy chimpanzees’, an early term for bonobos. The abstract actually compares Pan paniscus (bonobos) and Pan troglodytes (chimps) as if just to resolve your dilemma:
The external genitalia of four adult female pygmy chimpanzees (Pan paniscus) were examined during a 2-year period. It was found that the labia majora are retained in adults of this species and that, when tumescent, the labia minora effectively relocate the frenulum and clitoris so that they point anteriorly between the thighs. When detumescent, the configuration of the labia minora and clitoris resembles that of immature common chimpanzees (P. troglodytes). It is suggested that the simple, structural relocation of the clitoris from the normal [sic] condition noted in adult P. troglodytes makes possible the homosexual, intergenital rubbing observed in P. paniscus, when ventroventral juxtaposition of the individuals permits eye-to-eye contact. In addition, this change probably increases sexual stimulation of the female during heterosexual, ventroventral copulations.
Jacinta: Wow. So bonobos separated from chimps between 1 and 2 million years ago. And in that time a kind of structural change took place in the positioning of the clitoris. Is that plausible? And what about the swelling?
Canto: Hard to get clear info, but the general genital swellings of chimps versus bonobos differ in one respect – in chimps, they’re indicative of fertility, or ovulation, but bonobos, like humans have ‘concealed’ ovulation. A wonder that this can occur in the relatively short time since the split. Or maybe not, I’m no primatologist.
Jacinta: Apparently bonobos and humans aren’t the only primates with concealed ovulation – it also occurs in Vervet monkeys, but the very concept of ‘concealed ovulation’ is a bit controversial – as if it’s being done deliberately, which would surely be absurd. But it certainly does mean that, in those primates that don’t exhibit clear signs of ovulation, copulation occurs through all stages of the menstrual cycle. It could be a way of preventing males from being aware of their own offspring, thus reducing the infanticidal tendencies found in male, and sometimes female, chimps. As for the position of the clitoris, its shift to a more ‘accessible’ spot for genito-genital rubbing in bonobos is often mentioned as a great development for female bonding, but I can find nothing much on how this anatomical change could’ve happened.
Canto: Well, think of Darwin’s finches in the Galapagos. Certain beak shapes were more adaptive to the particular vegetation on particular islands, and birds with those beak shapes outbred other birds and became dominant, and ultimately the outright winners. With bonobos, okay this different clitoral positioning might not have led directly to those females outbreeding other females, since it might not have made it easier for males to have sex with females (though where there’s a willie there’s a way), but it might have led indirectly to females becoming dominant through sexually stimulated female bonding, allowing the females with the most changed and, to females, most alluring clitorises to choose the most male partners and so produce the most offspring.
Jacinta: Female rather than male choice. Or even females ‘sexually assaulting’ males? Definitely sounds interesting. But as always, more research is required…
References
Rebecca Wragg Sykes, Kindred: Neanderthal life, love, death and art. 2020
https://pubmed.ncbi.nlm.nih.gov/3985376/
https://en.wikipedia.org/wiki/Strepsirrhini
https://en.wikipedia.org/wiki/Macaque
https://en.wikipedia.org/wiki/Bonobo
https://www.scientificamerican.com/article/bonobo-sex-and-society-2006-06/
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