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The sad fate of Darwin’s sexual selection theory

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… even at its best. (Here we will avert our eyes as Ooga! Ooga! Big Spender! blunders by, choosing to focus instead on efforts by serious people.) Like this claim that “choosiness” is theoretically under direct sexual selection:

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black-cheeked lovebirds/ Snowmanradio (talk)

Abstract: Most theoretical research in sexual selection has focused on indirect selection. However, empirical studies have not strongly supported indirect selection. A well-established finding is that direct benefits and costs exert a strong influence on the evolution of mate choice. We present an analytical model in which unilateral mate choice evolves solely by direct sexual selection on choosiness. We show this is sufficient to generate the evolution of all possible levels of choosiness, because of the fundamental trade-off between mating rate and mating benefits. We further identify the relative searching time (RST, i.e. the proportion of lifetime devoted to searching for mates) as a predictor of the effect of any variable affecting the mating rate on the evolution of choosiness. We show that the RST: (i) allows one to make predictions about the evolution of choosiness across a wide variety of mating systems; (ii) encompasses all alternative variables proposed thus far to explain the evolution of choosiness by direct sexual selection; and (iii) can be empirically used to infer qualitative differences in choosiness

From Conclusion: Because direct sexual selection has the potential to generate all possible levels of choosiness, we encourage theoreticians to consider it as a crucial process determining the evolution of mate choice. Nevertheless, this does not mean that direct sexual selection is the only force acting on choosiness. Other selective pressures influencing the evolution of mate choice may play an important role, such as indirect selection [6,7,9–12], natural selection on choosiness [11,29–33] or antagonistic selection between the sexes [72,73]. All these processes can be described in terms of genetic variances, covariances and selection gradients within a quantitative genetic formalism [1,2]. Because direct sexual selection alone is considered in our model, within such a formalismall these variables are assumed to be null except the variance of choosiness and the sexual selection gradient on choosiness. Thus, our model probably represents the simplest model of sexual selection of mate choice one can conceive. We therefore suggest that the aforementioned mechanisms should be studied in addition to direct sexual selection as modifications of our basic model, rather than in isolation.

Somehow one doubts that in a world where most organisms have no capacity or opportunity for choice, a “choosiness” theory will fulfil its authors’ ambitions.

See also: Is there a real neutral theory of evolution? (His much more famous theory of natural selection is under intense fire from within the discipline too.)

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It wasn't Darwin's fault. It never is.
Darwin's switch to competitive selection has had a lasting and significant impact on evolutionary theory, a significance that I suspect has not been fully understood. Emphasizing competition led Darwin away from an understanding of species, laid the foundations of competition in ecology, and determined the course of evolutionary theory thereafter. Another influence has been to initiate the unmatched effort devoted to sexual selection in its various guises. An aspect of this is the tendency to regard anything to do with propagation as under the purview of sexual selection, and hence connected to competition. However, if we read carefully Darwin's account of sexual selection, we see that this is not a deficiency that can be laid at Darwin's door; it derives from later generations. - Hugh Paterson, The competitive Darwin
tjguy, the article questions whether sexual selection and female choice is behind the evolution of masculine faces, NOT whether sexual selection is operative in human evolution or other animals. Also, sexual selection should not be considered a subset of natural selection, because sexual selection was proposed by Darwin exactly to explain phenomena that couldn't be explained by natural selection. Natural selection can work in opposition to sexual selection so it makes no sense to call sexual selection a subset of natural selection. Last, sexual selection is explicitly agentic in that it proposes choice as the basis for this type of selection. So it is explicitly non-zombie in its mechanisms. Natural selection is non-agentic because it's simply the result of the sum of environmental forces acting on organisms and populations. aramis720
Interesting article on sexual selection:
Rob Brooks, an evolutionary ecologist at the University of New South Wales, in his book entitled The Conversation, took on the question, “Why the masculine face?”. Looking into the genetic crystal ball, leafing through the Darwin handbook, he set out to tell mankind why men have masculine facial features. Trouble is, there are no clear answers (evolutionarily speaking). For every John Wayne there’s a Justin Bieber. Exceptions abound, and evolutionists disagree among themselves. What value, then, does evolutionary theory bring to this kind of question? In their explanations, evolutionists focus on “reproductive success” – what processes result in not just more offspring, but more offspring carrying the genes for the trait supposedly selected by the opposite sex. Sexual selection becomes a subset of natural selection. Because selection is mindless and purposeless, their focus has the effect of discounting all the mental reasons for human mate choice, or worse, reducing even the mental reasons themselves to expressions of genes. This effectively turns people into zombies, pawns of evolutionary forces.
http://crev.info/2014/01/sexual-selection-is-a-zombie-idea/#sthash.CI59wUtP.dpuf In the end, Brooks admits the evidence that female mate choice drives that sexual selection so that masculine faces are selected for "is far from settled.” In other words there is lots of conflicting evidence. ie - no evidence yet. Brooks continues: "This is one of those ideas with prurient appeal, but patchy evidence. It’s morphing into what my UNSW colleague Angela Moles calls a ‘Zombie Idea’: compelling and considered self-evidently true by many, but not actually that well supported." "Every link, from the attractiveness of masculine facial features to the immunosuppressive nature of testosterone to the claim that masculine-looking men have good immunity genes is contested. We don’t know how big the genetic benefits to children might be, much less whether they can offset the costs to a woman of mating with a highly masculine man." "The extensive genetic variation in masculinity makes more plausible the idea that choosing to mate with a masculine man can result in more attractive offspring. But the genes that made a male face more masculine did not make it more attractive. Worse, these same genes made female faces more masculine and thus less attractive. Families that make manly-looking sons tend also to make masculine-looking daughters." In the end, Brooks can affirm nothing scientifically: “Much about the variable preference for manliness and for bad boys remains to be explained. Much, I fear, might be inexplicable.” Commentary: "The whole promise of Darwin to the scientific community was supposed to be the offer of a mechanistic, non-theological explanation for any given biological trait. OK; so 154 years later, what does it explain face to face? Nothing! We are told, “Could be this, could be that, could be a combination, or might be inexplicable,” they waffle. “With more funding maybe someday we can figure it out.” tjguy
I'm not sure how serious anyone should take your critique of sexual selection theory when all you offer as a rebuttal is this: "Somehow one doubts that in a world where most organisms have no capacity or opportunity for choice, a “choosiness” theory will fulfil its authors’ ambitions." Have you observed animals in nature? Have you observed humans in nature? Choices are made everyday all day, including sexual mating choices. aramis720

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