Copulation calls

chimpFemale chimps make noise while fucking - not every time they fuck, but often. Biologists want to know why: why they ever make noise while fucking; why they don't always make noise while fucking. In other words, they want to know what the noises are for.

One explanation that few biologists entertain is that noises made by female chimps while fucking have no effect on anything, and so are not for anything at all. This explanation is scientifically implausible: making noise while fucking is bound to have some effects, as the noise is heard by chimps and non-chimps in earshot. Chimps have rather few predators and are not primarily hunters, so biologists ignore the non-chimps and focus on the chimps. Among the chimps, they focus on those that matter - not the infants, juveniles, or adolescents, but the low-ranking and, especially, high-ranking males and females whose protection is worth having, whose animosity is worth avoiding.

By making noise while fucking, female chimps let any chimps who matter who are in earshot know that they are fucking. The question, 'What are the noises for?' thus becomes the question, 'What effect does it have when a female chimp lets any chimps that matter in earshot know that she is fucking?' The male chimp being fucked then drops out of all consideration; he already knows the female is fucking, for he is being fucked by her. The noises can't tell him anything he doesn't know already. So the noises must be directed at the wider audience - not the male chimp being fucked but the other chimps, and especially the high-ranking ones, in earshot.

Biologists, hampered by the explanatory requirements of their discipline, are forced to reconfigure the question, 'What are the noises for?' in this way. They cannot accommodate the thought that noises made by female chimps while fucking express pleasure. But chimps are closely related to humans; noises made by humans while fucking are known to be expressions of pleasure; so it is very likely that the noises made by female chimps while fucking express pleasure as well.

If the noises made by female chimps express pleasure, then the most likely audience for them is the one the biologists are forced to ignore - the male chimp being fucked. This is a neat account of what the noises are for, in my view. It explains straightforwardly why female chimps only sometimes make noise: only some fucks are pleasurable. But pleasure is biologically inert, and cannot be measured. This kind of account is irremediably unscientific. It cannot be confirmed or falsified. We cannot establish that the noises made by female chimps while fucking express pleasure, or that they do not, unless we have a way to tell whether the fucking is pleasurable or not that does not depend on listening to the noises the female chimps make. And we have no such way to tell. Human females tell us that they enjoy fucking not just by the noises that they make while fucking but also when we ask them whether they enjoy it. They can confirm that, yes, they moan or gasp or wail or cry because it feels so good, and the moans and gasps and wailsand cries express that pleasure. We can't ask the female chimps if they enjoy fucking, so we can't confirm, or deny, that the noises they make while fucking express pleasure.

We might, though, have evidence that counts against the 'expression of pleasure' explanation in its simplest form. A recent study, published in the online journal PLoS One and written up in the New York Times and other newspapers, found that female chimps are noisiest while fucking high-ranking males, and quietest when high-ranking females are in earshot. This suggests that the noises are not simple registers of pleasure. Why should fucking high-ranking males be more pleasurable than fucking low-ranking males? And how could the fact that high-ranking females are in earshot make fucking less pleasurable than it would otherwise be?

To take the first question first: high-ranking males might be better fucks than low-ranking males. Perhaps one way males gain rank is by being a superior fuck. If so, the females may prefer fucking high-ranking males just because it is more pleasurable. But it is not here the rank that really matters; the males are good to fuck, and so gain rank, but gaining rank does not make them any better to fuck. Or perhaps high-ranking males are cockier, more relaxed, get fucked more and so are more experienced at being fucked, better to fuck, and so on. Here rank really matters, because gaining rank makes a male a better fuck, losing rank makes a male a worse fuck. The 'expression of pleasure' explanation need not be abandoned because females are noisiest when fucking high-ranking males. But the fact that female chimps are quietest when high-ranking females are in earshot suggests that the noises made by female chimps while fucking are under some control; female chimps can fuck quietly when they have reason to. This is turn suggests that they can fuck noisily when they have reason to. If a fuck is really good, they can keep quiet about it. If a fuck is bad, they can still make a noise about it. This complicates the question, 'What the noises are for?' considerably. But I do not think it dooms the 'expression of pleasure' account of the noises altogether.

Suppose that the noises female chimps make while fucking communicate pleasure, rather than simply expressing it; suppose, in other words, that male and female chimps who hear the noises understand them as expressions of pleasure. Suppose also that communications of pleasure from a female while fucking are pleasurable to the male she is fucking, perhaps by increasing the pleasure of the fucking itself, or by making the male chimp feel good in some other way. The males are pleased by the pleasure of the females. The females communicate their pleasure to please the males. Were all this so, faking it while fucking high-ranking males would make perfect sense. The high-ranking males are the males to please above all others - the males whose protection is most needed, whose animosity is most to be avoided. These males will be pleased by communications of pleasure from females while fucking them whether those communications reflect the pleasure of the female accurately or not. So the females have good reason to fake it.

If female chimps sometimes fake it, that helps explain why female chimps are noisiest when fucking high-ranking males. We know that female humans sometimes fake it, and humans are closely related to chimps. So it hardly seems unreasonable to suppose that sometimes - when they have reason to - female chimps fake it too.

Why, though, are female chimps quietest when high-ranking females are around? Shame, perhaps, or just embarrassment. Perhaps they don't want to hurt the other female chimps' feelings, or don't want to make them jealous. Perhaps it is a gesture of respect, or deference. Or perhaps trying to be quiet makes fucking more pleasurable, or the female chimps enjoy fucking on the sly. We are used to these kinds of feedback loops between pleasure and its expression in humans; perhaps something like it goes on with the chimps.

This whole account, however, is biologically inert. Pleasure, expression, communication, understanding, faking, shame, embarrassment, sympathy, jealousy, respect, secrecy: every one of these categories is scientifically intractable, and hence useless in scientific explanation. Biologists can do nothing with them. Instead they explain the noises female chimps make while fucking in terms of effects on survival and especially reproduction: by making noise while fucking, female chimps advertise their sexual receptivity to other males, in order to get to fuck those other males, in order to confuse paternity; or they advertise, in order to fuck other males, in order to bring about sperm-competition; or, by making noise while fucking, female chimps incite male-male competition, in order to bring about a more efficient sorting by rank among the males, in order to then select the best males to fuck; by being quiet while high-ranking females are around, female chimps minimize female-female competition, in order to improve access to high-ranking males, or gain the co-operation of powerful females. To the biologists, the audience for the noises female chimps make while fucking cannot be the male chimp being fucked, for that male surely knows he is being fucked anyway. The noises must serve to alert other chimps that fucking is going on, and the benefits of so alerting those chimps is what the noises are for.

I prefer to think that the noises female chimps make while fucking are communications of pleasure, directed mainly at the male being fucked. That is what I think about noises made by female humans; why not think the same of female chimps? In the human case, these communications of pleasure are sometimes sincere, even if they are sometimes insincere. If female chimps enjoy fucking - and why wouldn't they? - these communications of pleasure are sometimes sincere as well.