March 15, 2021 | Jerry Bergman

Sexual Selection Fails to Explain Beauty

 

Explaining Beauty in the Natural World by Sexual Selection:
It Has Proven to be an Exercise in Futility

by Jerry Bergman, PhD

It has been a century and a half since Darwin published his The Descent of Man, and Selection in Relation to Sex. That sexual selection was a major part of the title illustrates how important this mechanism was to Darwin in attempting to explain human evolution. Biologist Ronald Fisher[1] wrote in 1915 that of the “branches of biological science to which Charles Darwin’s life-work has given us the key, few, if any, are as attractive [important] as the subject of Sexual Selection.”[2] This statement is still valid today.[3] An important question Darwin attempted to answer in The Descent of Man was: why do modern humans look so different physically from that of our ape ancestors?

Mandarin ducks, male (left) and female (right), illustrating the dramatic difference between sexes. (Wiki Commons)

Darwin argued that sexual selection explains the difference between the sexes in sexual organisms from eukaryotes to humans. Sexual selection not only produces sexual dimorphism, but also aids the evolutionary process, he thought. Sexual selection must have been active therefore in the transformation from apes to humans. To Darwin, sexual selection provided a solution to criticisms that differences in appearance of his postulated transitional forms were too great to connect us to ape ancestors. In truth, the apes would not be considered paragons of beauty today. Sexual selection gives evolutionists a theory to explain how hairy apes transformed into the physically attractive humans we see all around us now.

A commentary about this by Michael Ryan, published in PNAS on 25 February 25 2021, represents yet another attempt to justify Darwin’s sexual selection theory.[4] Sexual selection was no small part of Darwin’s theory. He considered it essential not only for human evolution, but for the evolution of all animal life. The core of his theory includes both natural selection and sexual selection, as is clear from Darwin’s book titles. Thus, defending sexual selection has always been an important part of supporting Darwinism.[5]

The problems with sexual selection theory are obvious throughout Professor Ryan’s review. For example, as he explained,

Darwin suggested that in many cases female preferences for elaborately ornamented males derived from a female’s taste for the beautiful, the notion that females were attracted to sexual beauty for its own sake.[6]

A major concern is why and how did females evolve a “taste for the beautiful”? And why the many very different specific tastes, which vary greatly throughout the animal world? Darwin’s explanation was:

when we see many males pursuing the same female, we can hardly believe that the pairing is left to blind chance—that the female exerts no choice, and is not influenced by the gorgeous colours or other ornaments with which the male alone is decorated.”[7]

This observation does not explain how and why the female evolved a specific “taste for the beautiful” which varies enormously.

The Problem with the Origins of the Taste for the Beautiful

Given that the core of evolution is reproductive success, all other factors being equal, the animals that had the greatest number of offspring would have an advantage in evolution.[8] Consequently, evolution would select for females with less fussy mate choices. The more rigorous the qualities females demand for mate choice, especially related to external beauty, the less likely mating would occur. As Ryan describes the problem,

You cannot reproduce if you do not survive; but if you survive and do not reproduce or help someone else reproduce you might as well be dead—at least from a Darwinian perspective.[9]

The sexual selectionists try to associate beauty with other positive traits that might aid survival. For instance, beauty might be associated with health (assuming that sick persons are considered less attractive), intelligence, and other mental traits.[10] The problem is, many studies contradict this claim. Ryan writes:

Most early studies in behavioral ecology have assumed that a male’s outer sexual beauty was indicative of his inner genetic quality, his “good genes” for survival. Studies rarely determined the effect of male traits on offspring survivorship or even proxies for survivorship but based their arguments on the demonstration that male traits were costly.[11]

A discussion of the peacock’s tale can be found in ch. 9.

For example, studies show that, in humans at least, “intelligence decreases the number of offspring and frequency of sex for both men and women.”[12]  Furthermore, for humans a positive correlation with offspring number exists for traits other than physical beauty, including land ownership, social status, age, power, hunting ability, political status, and education.

All of these factors mitigate the argument that organisms survive better by choosing mates that are physically attractive. Cultural factors appear far more important in determining mate preferences. These, moreover, are not due to inborn drives as Darwin assumed. This fact was recognized over a century ago. Fisher wrote “man, perhaps more than any other animal” has the ability to choose the right mate,[13] not only on the grounds of health, which is indicated by beauty, but also on intelligence, compatibility, education, and other qualities.

Fisher added that human sexual selection must “determine and choose the human types which on all grounds are the best, and the sexual selection of thousands of preceding generations.”[14] By the “best” he refers to a large set of traits, of which physical beauty is only one. For females, beauty is often not first on the list. A survey of males and females in both Western and Eastern countries found the number one trait desired for a mate for both sexes is kindness. Number two for females was the ability to support a family, and for males number two was physical attraction.[15]

The Status of Sexual Selection Theory

In 2009, Jones and Ratterman reviewed the status of Darwin’s sex theory. “Darwin provided partial answers to these [sexual selection] questions,” they wrote, “and the progress that has been made on both of these topics since his time should be seen as one of the great triumphs of modern evolutionary biology.” But then they admitted, “a review of the literature shows that key aspects of sexual selection [theory] are still plagued by confusion and disagreement.”[16]

The peacock in all its glory, admired by humans, but ignored by peahens. (Wiki Commons)

Even Darwin realized a major conundrum in his sexual selection theory. The visibility of beauty for attracting mates, such as bright colors, also results in greater visibility to predators. The peacock’s tail is a classic example. It attracts peahens, but also attracts predators. Moreover, the cost of carrying around that huge tail fan causes a major impediment in the peacock’s ability to escape from its enemies.

Darwin recognized this and, in a now-famous letter to botanist Asa Gray, complained that “the sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick!”[17] He realized his theory of natural selection could not explain the origin of traits that are clearly maladaptive for survival.[18] Additional research I cite in my book on Evolution’s Blunders reveals that the peacock’s train is largely irrelevant in mate choice.[19] Scientists who watched the birds were surprised to see that the peahens usually ignore the peacock’s flamboyant train.

Darwin’s sexual selection theory assumed that many sexually dimorphic traits must have been intimately involved with reproduction. He explained that they either helped the bearer to compete for access to mates, or enhanced the sexual attractiveness of the bearer.[20] Beyond this, his theory actually explained little else. What process causes divergence of traits seen in sexually dimorphic animals? Darwin said these traits were selected once they existed, but he largely failed to explain how they originated. How did the first peacock go from plain feathers to its bright colorful fantail display?

Comment: There are as many exceptions to sexual dimorphism as examples: for instance, crows in which both sexes are black. The sexual phenotypes of many birds, fish and mammals are almost indistinguishable. And in some cases of extreme sexual dimorphism, beauty is certainly not a factor!  —Ed.

Sexual selection was a target of criticisms by the co-originator of natural selection theory, Alfred Russel Wallace, among others. One of many issues they raised concerned Darwin’s generalities about mate choice. In sexually dimorphic animals, often the more elaborately adorned sex is the male. The traits that varied in form included the

melodious songs of birds, brilliant colors of fish, and the dances of spiders. Darwin posited that these traits evolved to charm females during courtship. However, critics countered that there was scant evidence to suggest that females were the ones who executed the mating decision, and even if that were true Darwin did not propose a convincing theory as to why females should be attracted to more adorned males. Darwin, in fact, did provide an explanation: He suggested that females had “a taste for the beautiful” and that males evolved traits that appeal to the female’s perception of sexual beauty. His critics found such an explanation wanting.”[21]

Is Mate Choice the Answer or the Question?

Ryan attempts to explain away this problem by stressing that new research puts female mate choice at the forefront, and variation in male mating success was correlated with variations in male display traits.[22] All this idea does is to restate the problem. The origin of female choice for flashy displays has to be explained as well as the evolution of the male trait.

Ryan examined 130 research studies in an attempt to solve this problem. Several studies he reviewed attempted to explain the evolution of female choice by postulating thatgene flow among populations of sexually reproducing species is an important modulator of evolutionary divergence, and reproduction is what usually makes genes flow.”[23] That is an empty claim. Gene flow does not explain anything. For the most part, it leads to degeneration of the genome. This idea, furthermore, ignores the problem; it does not solve it. As Ryan admits, “There has never been much consternation over why females would evolve such preferences” – but I say there should be much consternation because it is the central problem. [24]

In this review I have focused on female mate choice because Darwin believed that sexual attraction was primarily a female trait: i.e., females were attracted to males on the basis of their appearance. That is not always true. Both male mate choice and also mutual mate choice are common in the animal kingdom. We humans can relate to that.

Ryan then says, “Paralleling evolutionary studies of species recognition were those of neuroethologists exploring how animals extract and analyze biologically relevant information in the world around them.”[25] This observation reveals that the attraction drive is much more complex than it first appears. Once again, though, it does not solve the evolution of female preference. Ryan then expands the problem by adding additional factors. He notes that, in addition to sexual selection,

Social selection has many of the features of Darwin’s original notion of sexual selection and shares many of its differences with natural selection. It was against this background that behavioral ecologists resuscitated the field of sexual selection.[26]

Conclusion

Ryan concluded that 150 years “after Darwin suggested his idea of ‘a taste for the beautiful’ he would hardly recognize the research that this suggestion spawned.” The volume of literature about this, as Ryan documents, is enormous, but none of it answers the central question originally raised in this review, namely “why and how did females evolve a “taste for the beautiful”? Natural selection should generally favor animals that had the greatest number of offspring, thus would select for females with less fussy mate choices. The more rigorous the qualities required for mate choice, especially those related to external beauty, the less likely mating will occur.

The 120 research studies Ryan reviewed primarily described how complex mate selection is, not how it could have evolved. It has even been difficult to propose plausible just-so stories to explain how the “taste for the beautiful” arose. After 150 years of trying, it is unlikely that scientists will propose a better solution. The best explanation is that the secondary sexual traits were all part of the original design incorporated at the initial creation of each organism.

Now watch this short film from Illustra Media: Beauty, Darwin, and Design.

Source: The John 10:10 Project.

References

[1] Richard Dawkins considered Fisher the greatest biologist since Charles Darwin. https://www.famousscientists.org/ronald-fisher/.

[2] Ronald A. Fisher. 1915. The evolution of sexual preference. Eugenics Review 7(3):184-192.

[3] Prum, Richard. 2017. The Evolution of Beauty.  How Darwin’s Forgotten Theory of Mate Choice Shapes the Animal World—and Us. New York: Doubleday.

[4] Ryan, Michael. 2021. Darwin, sexual selection, and the brain. PNAS  118(8): e2008194118; https://doi.org/10.1073/pnas.2008194118.

[5] Prum, 2017.

[6] Ryan, 2021, pp.1-2.

[7] Darwin, Charles. 1871. The Descent of Man, and Selection in Relation to Sex, Part I, Princeton University Press, Princeton, NJ, p. 421.

[8] Bergman, Jerry. 1990. The Fall of the Natural Selection Theory.  Proceedings of the Second International Conference on Creationism, Pittsburgh, PA, pp. 37-42, August.

[9] Ryan, 2021, p. 2.

[10] Bergman, Jerry. 1992. Some Biological Problems of Natural Selection Theory.  CRSQ 29(3):146-158, December.

[11] Ryan, 2021.

[12] Hopcroft, Rosemary L. 2006.  Sex, status, and reproductive success in the contemporary United States. Evolution and Human Behavior 27(2):pp. 104–120, March.

[13] Fisher, 1915, p. 189.

[14] Fisher, 1915, pp. 190-191.

[15] Luscombe, Belinda. 2019.  Here’s What Young People All Over the World Say They Want Most in a Partner. Time Magazine, September 13.

[16] Jones, Adam and Nicholas L. Ratterman. 2009. Mate Choice and Sexual Selection: What Have We Learned Since Darwin? In: In the Light of Evolution: Volume III: Two Centuries of Darwin. The National Academies Press, Washington, D.C.  Emphasis added.

[17] Darwin, Charles. 1860.  Letter 2743 on the Darwin Correspondence Project. Cambridge University Library, University of Cambridge, UK; https://www.darwinproject.ac.uk/ entry 2743.

[18] Ryan, 2021, p. 1.

[19] Bergman, Jerry. 2017. Evolution’s Blunders, Frauds and Forgeries. Chapter 9: “Darwin’s Peacock Tail Proof of Sexual Selection Myth,” CMI Publishing, Atlanta, GA, pp. 129-140.

[20]  Ryan, 2021, p. 1.

[21] Ryan, 2021, p. 2.

[22] Ryan, 2021, p. 2.

[23] Ryan, 2021, p. 2.

[24] Ryan, 2021, p. 2.

[25] Ryan, 2021, p. 2.

[26] Ryan, 2021, p. 2.


Dr. Jerry Bergman has taught biology, genetics, chemistry, biochemistry, anthropology, geology, and microbiology for over 40 years at several colleges and universities including Bowling Green State University, Medical College of Ohio where he was a research associate in experimental pathology, and The University of Toledo. He is a graduate of the Medical College of Ohio, Wayne State University in Detroit, the University of Toledo, and Bowling Green State University. He has over 1,300 publications in 12 languages and 40 books and monographs. His books and textbooks that include chapters that he authored are in over 1,500 college libraries in 27 countries. So far over 80,000 copies of the 40 books and monographs that he has authored or co-authored are in print. For more articles by Dr Bergman, see his Author Profile.

 

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