Let me start this off with a quote from Charles Darwin:
I have been struck with the likeness of many of the half-favourable criticisms on sexual selection, with those which appeared at first on natural selection; such as, that it would explain some few details, but certainly was not applicable to the extent to which I have employed it. My conviction of the power of sexual selection remains unshaken; but it is probable, or almost certain, that several of my conclusions will hereafter be found erroneous; this can hardly fail to be the case in the first treatment of a subject. When naturalists have become familiar with the idea of sexual selection, it will, as I believe, be much more largely accepted; and it has already been fully and favourably received by several capable judges.
(Descent of Man, preface)
And now let’s look at this news story that has as its focus a “challenge” to sexual selection.
“If you have a theory that says something is wrong with so many people, then the theory is suspect,” says Joan Roughgarden, looking up from her Caribbean chicken salad. “It is counter-intuitive that nature should have done such a bad job – or, if you prefer, that God should have made so many mistakes.”
The theory in question is Charles Darwin’s theory of sexual selection; the “mistakes” are homosexuals, bisexuals, transsexuals – anyone who does not fit into the neat categories of heterosexual male and female.
By challenging the great 19th-century naturalist, Roughgarden, a professor of biological sciences and geophysics at Stanford University, is making waves in academia and beyond. The implications, not only for science but also for society, could be profound. After all, you don’t need to be versed in the Origin of Species to share Darwin’s twin assumptions that, broadly, the purpose of sex is reproduction and that females select mates on the basis of genetic characteristics or traits.
Being versed in Darwin studies would mean that one would know that instead of Origin of Species one should be looking at Descent of Man for Darwin’s full explication of his theory of sexual selection. And when one looks there, does one find that sexual selection is founded strictly upon the two “assumptions” identified above? No, one does not.
The first assumption, that the sole purpose of sex is reproduction, is simply absent from Darwin’s work, so far as I can determine. Someone may have advanced that notion, but until I am presented with the particular passage from Darwin that confirms it I will remain unconvinced of the veracity of the claim that it is Darwin who advanced it. To this end, I have examined etexts of both Origin of Species and Descent of Man and have satisfied myself that such a passage is not to be found within these works.
Let’s look at how Darwin framed sexual selection.
We are, however, here concerned only with sexual selection. This depends on the advantage which certain individuals have over others of the same sex and species solely in respect of reproduction. When, as in the cases above mentioned, the two sexes differ in structure in relation to different habits of life, they have no doubt been modified through natural selection, and by inheritance limited to one and the same sex.
(Descent of Man)
There is no dependence given here by Darwin on sex itself having the purpose of reproduction, as represented by Roughgarden. Instead, Darwin presents sexual selection as a function of differential reproductive success — which says nothing about what the “purpose” of sex itself is.
What of the second assumption identified by Roughgarden, that of female choice? That certainly is part of Darwin’s theory of sexual selection. The problem lies not in what Roughgarden provides here, but in what she omits. Sexual selection as explicated by Darwin also concerned how the traits found in the males affected male-male interactions.
When the two sexes follow exactly the same habits of life, and the male has the sensory or locomotive organs more highly developed than those of the female, it may be that the perfection of these is indispensable to the male for finding the female; but in the vast majority of cases, they serve only to give one male an advantage over another, for with sufficient time, the less well-endowed males would succeed in pairing with the females; and judging from the structure of the female, they would be in all other respects equally well adapted for their ordinary habits of life. Since in such cases the males have acquired their present structure, not from being better fitted to survive in the struggle for existence, but from having gained an advantage over other males, and from having transmitted this advantage to their male offspring alone, sexual selection must here have come into action. It was the importance of this distinction which led me to designate this form of selection as Sexual Selection.
(Descent of Man)
Not only does Darwin recognize male-male interactions here, but he emphasizes the importance of these in his development of the theory of sexual selection. That seems a rather glaring oversight on Roughgarden’s part.
Consider this from the same interview with Roughgarden:
Her alternative paradigm, presented in Evolution’s Rainbow, starts with evidence that the natural world is more sexually diverse than usually appreciated. For example, about a third of the species of tropical fish swimming over coral reefs change sex at some point during their lifetime. The conclusion, she says, is that our tendency to divide creatures into neat piles labelled “male” and “female” is mistaken.
It’s funny how Roughgarden positions herself as breaking new ground in discussing diversity of sexual habits. It becomes especially funny when one peruses both Origin of Species and Descent of Man and finds the many discussions of hermaphroditism, gender change, and parthenogenesis contained therein.
Further on in the article on Roughgarden, we find this:
Roughgarden isn’t suggesting an overhaul of Darwin’s theory of sexual selection – she is proposing demolition and redevelopment. Her explanation is that Darwin was wrong to regard sex as solely a matter of reproduction. It also has a social role. Thus homosexual behaviour, she says, is a way of building same-sex relationships and strengthening the position of an individual within a group. Far from being an anomaly, she says it is widespread and useful.
It would appear that strawman construction and demolition is not only useful for career-building, but also seems to be lucrative, if book royalties amount to anything. Compare the grandstanding that comes through this text to Darwin’s own assessment of sexual selection quoted up at the top of this post. The comparison is not favorable to Roughgarden.
Roughgarden’s thesis of the social utility of homosexuality should properly be considered as complementary to Darwin’s theory of sexual selection rather than as a supplanting alternative theory. For while Darwin did not treat characters like homosexuality directly, there is nothing within what Darwin actually wrote on the topic that would exclude social behaviors of this sort from the general framework of sexual selection. But that, of course, would not give Roughgarden the iconoclast status that she apparently seeks.