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There's something I heard, again, a while ago that I kind of want to talk about now. The first time I heard it, it was from a primatologist, and this statement is part of the reason I sometimes have difficulties with primatologists. I have also seen it quoted online, though, in the years since bonobos became the animal of the day. (Now it's the honey badger.) The statement is, roughly, this: Bonobos are more sexually/interpersonally evolved than other animals on account of the fact that they have sex while facing each other.
Bonobos have only been identified as a species for a little over half a century or so, depending on who you ask. They have only been intensely researched for a few decades. Zoologists and comparative psychologists were of course astounded by the unique behaviour of the species: in contrast to their close chimpanzee relatives, they are quite nonviolent, females hold a lot of power, and they have lots and lots of crazy sex. They have sex for many reasons: they have sex to calm everyone down, to build relations, or even to exchange favors. They have sex with the opposite sex; they have sex with the same sex. They have sex with their juveniles. And, what was for some reason astonishing to researchers, they have sex in the missionary position.
The reason given was that because they are having intercourse face-on, it must add to the idea that sex in bonobos, like in humans and unlike in nearly every other animal, must play a very important social role and may even suggest a loving context. After all, the face is the main outlet of emotion in primates, and we are a highly visual taxonomic order. I say they are fascinated, "for some reason," though, because of this
this
and even this
Ignoring the fact that I probably have far too many pictures of lions at quick access, most ethologists would tell you that there isn't a whole lot going on between a male and female lion when they're doing their thing up to fifteen times a day. Lions are also not terribly visual: they rely mostly on smell, like most mammals. So what exactly is the deal here?
Well, as for why animals do it... we're not entirely sure. Quite possibly, as it is with humans and weird positions, it's just a cool thing to do. As for why some don't, though, or don't that often, it comes down to anatomy: if you've ever looked at a dog on his or her back, they're not quite as, erm, accessible as is a human on his or her back. Any effort to make them more so would likely lead to at least some discomfort, particularly if you are a quadruped, with a quadrupedal spinal structure: you would need to have your entire body on top, pressing all the limbs that normally want to stick up back down, and things get way more complicated than is generally worth it. In addition, a female is more prone on her back, and unable to escape. A little more controversial, perhaps, but when you consider that rape seems much more common among apes, including humans, than quadrupeds, it may be that the missionary position developed to keep females safe and males "productive" among those species were rape is more frequent.
In any case, some primates in particular seem to have evolved towards the missionary position. The spines of Old World apes are more erect. Our limbs are very flexible. Apart from humans, there is no animal that better exemplifies these crucial qualities than the bonobo.
On a side-note, and as an excuse for one more picture, have you ever wondered why human women have much larger breasts for their size than those of any other mammal? It's not because of milk production: breast size has no impact on that. It's not a conspiracy orchestrated by Playboy, either. (Or is it?) It's because they make a pretty great cushion in the missionary position, just as big butts do so in "doggy-style". (see Desmond Morris, The Naked Ape, 1967) And bonobos look to be heading in that direction.
So, is there something special about the missionary position? Quite honestly, not one bit. It's a side-effect of the anatomy that evolution has given us, and bonobos just happen to be on a similar pathway. Sorry, bonobo fans.