If Elisabeth Lloyd’s take on the female orgasm is correct—i.e. if it is homologous to the male orgasm—then FEMALE ORGASM is not a proper evolutionary category. Homology is sameness. Hence, male and female orgasms belong to the same category. The orgasm is an adaptation, whether male or female (and Lloyd should agree). It is not a spandrel or by-product.
I’ll get back to this in a moment, but first some background. There are five NewAPPSers who have a particular interest in the philosophy of biology. Roberta Millstein, Helen De Cruz, Catarina Dutilh Novaes, John Protevi, and myself. Aside from Roberta, each of us comes at it from a related area in which biological insight is important. For me, that area is perception. I have written quite a bit about biology, but my mind has always been at least half on the eye (and the ear, and the nose, and the tongue, . . .).
There is a divide among us with respect to a leading controversy in the field. Catarina is strongly anti-adaptationist and I am strongly adaptationist (perhaps because of my motivating interest in perception, which is exquistely adaptive). Roberta, Helen, and John are somewhere in between, but likely closer to Catarina than to me. You can gauge where I stand when I tell you that in my view, Gould and Lewontin’s 1979 anti-adaptationist manifesto, “The Spandrels of San Marco and the Panglossian Paradigm” is one of the worst, and certainly one of the most mendacious, papers I have ever read in any field. Among the five of us, I am sure I am alone in this.
Given all of this, my take on adaptationism with regard to the orgasm may get a hotly negative response from my co-bloggers. Nevertheless, I’ll get on with it.
I’ll start with a contentious way of putting my point. Female sex organs are products of different but homologous developmental pathways. The orgasm in females comes from the same hormonal and physiological causes as in males. In the case of the orgasm, the male and female versions are the same biological phenomenon, albeit phenotypically somewhat modified across the sexes insofar as the surrounding physiology and hormonal structure is different. This is Lloyd’s story, and I accept it. It implies that it is a mistake to ask whether the female orgasm is an adaptation.
All right, dear reader, you may find what I have said unintuitive. Let me try to back you into this by directly addressing the crucial move in Catarina’s argument. She observes that only a small number of females experience orgasm “systematically and reliably,” perhaps only 30% to 10%. And so, she asks, “how can anyone claim that a given trait is an adaptation, if it is in fact so scarcely represented in the population in question?”
Hold on just a minute! What is “the population in question?” Among sexually reproducing organisms, a population is an interbreeding group. It is closed under interbreeding in the sense that if a belongs to a population, P, and if b is fully capable of breeding with a, then b also belongs to P. (Some birds breed across populations, but they are strongly disposed against this, for whatever reason—I will assume that they are not “fully” capable.) No group of homo sapiens containing only females would be a population, then.
Given that the population is the locus of selection, and given, further, that males are an integral part of the population, how should we go about finding out whether “human females having this trait [i.e., orgasm] would have been selected for over those who did not?” There are, I think, three kinds of possibility.
1. Female orgasm could be a recessive X-linked trait. If so, mothers would pass it on to daughters but not to sons. Here, we can ask Catarina's question: are orgasmic females more fit? However, we exclude this possibility because we are assuming (following Lloyd) that orgasm is homologous across the sexes.
2. Orgasm could be passed from both parents to offspring of both sexes (like height or skin colour). In this case, if a more orgasmic mother had more orgasmic sons, then conceivably “human females having this trait would have been selected for over those who did not” (assuming that their sons would have a reproductive advantage).
3. Finally (what I take to be the actual case) assuming that orgasms are functional for males and non-functional for females, it is selected-for because males who have the capacity have more offspring than males who do not. But then orgasm is selected-for; it is an adaptation.
Here’s the bottom line. Elisabeth Lloyd, whose work on the female orgasm Catarina justly admires, is properly taken to be arguing against the thesis that orgasms have a distinct function in females. This is very different from arguing that it is not an adaptation.
Now, let’s come to deductive reasoning. As we have seen, Catarina says that female orgasm can’t be an adaptation because only a small proportion of females reliably have an orgasm (during intercourse). She reapplies this argument to deductive reasoning. Since not all humans can (or do) reason deductively, deductive reasoning cannot be an adaptation. I hope I have shown that this argument doesn't work. In a polymorphic population (i.e., one in which there are diverse types) a trait can be selected because it helps a sub-type.
This indicates why you can’t assume that an adaptation will be universal. There are stable polymorphisms that are maintained by frequency-dependent selection. Some of the types in such a polymorphism might occur with very low frequency.
For instance: Is sterility adaptive? You might think not, by definition. E. O. Wilson showed why this is wrong. Given the right system of inheritance, and given a polyfunctional group, it could work for a sub-group. That sub-group may promote its own genes by some means other than reproduction. Given the right conditions, sterility would maintain a steady proportion, and would rightly be regarded as an adaptive feature of the social system.
I am not saying that any of this is true for deductive reasoning. The ability to reason is not my quarry here. (For what it is worth, I think it's a part of human recursion, which is universal, but highly environment-sensitive.)
What I want to say is this: Don’t buy uncritically into the Gould-Lewontin rhetoric. Adaptationism isn't stupid.
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