October 23, 2023 | Jerry Bergman

Does Darwin’s Theory of Sexual Selection Explain Anything?

It does not explain the origin of new traits,
but only the frequency of some existing traits



by Jerry Bergman, PhD

One of Darwin’s major arguments to explain the origin of traits that did not have any obvious advantage in the competition for survival was sexual selection. Sexual selection is a type of natural selection in which members of one biological sex prefer to mate with members of the other sex that have certain traits, such as birds adorned with bright colors. The result, Darwin predicted, is that the birds with bright colors will be more likely to mate and, consequently, produce more offspring than animals lacking bright plumage. In time, the bright-colored birds will become numerically more common. Eventually, the dull colored birds will become rare and, in many cases, extinct.[1]

The peacock in all its glory, admired by humans, is the icon of sexual selection. Some scientists have observed that the flamboyant tail feathers are generally ignored by peahens. (Wiki Commons)

Unvalidated Assumptions

One problem with sexual selection was brought up in a paper in PLoS Biology. Emily DuVal and colleagues, who try to “improve” sexual selection theory, point out some weaknesses with sexual selection as it has been long taught.

Predominant mate choice theories assume preferences are determined solely by genetic inheritance, an assumption still lacking widespread support.[2]

Another problem they speak of is the fact that

mismatches between theoretical and empirical patterns demonstrate that mate-choice models still lack critical components of the process by which preferences arise and are elaborated.[3]

In other words, the specific theory of how sexual selection functions is not supported either by theory or by field data.

The difficulty of untangling all the factors that might influence mate choice makes the theory hard to test. When a male is chosen, it is often unclear why that individual was favored, because phenotypic variation is complex and often multimodal. In humans, the attraction to a woman could be her feminine face, her stunning female figure, her warm smile, her brown eyes, her soft sexy voice, her academic achievements, her engaging personality, her stimulating conversations, or many other factors. Attraction is likely a combination of all of these factors, but it is very unlikely that each of these factors make equal contributions.

Another issue that complicates sexual selection is that men are often attracted to women who have characteristics like their mother, and women are often attracted to men who remind them their father.[4] This non-Darwinian fact would tend to perpetuate familiarity over novelty. Additionally, women consider whether or not they feel the man would be a good father, whether or not he is handsome.[5] Which factors are more important, and which are of only minor importance, has been a major unsolved problem in sexual selection theory. An example will be detailed below.

The Contrast Between Theory and My Experience

Sexual selection seems logical and, in contrast to many parts of Darwin’s theory, appears plausible—in theory. But my experience led me to question whether it explains anything.

As a young man, I worked as a professional photographer for several years in the area of commercial photography. My work involved taking pictures of automobiles, shoes, wine, and numerous items for advertising in magazines, newspapers, and car catalogs. For most of the shots we hired a female model to stand by the door of the Dodge or other items that we were photographing. We and advertisers knew from extensive market research that attractive females drew the attention of both men and women. Selecting the right female model, therefore, was critical.

Nose shape classification, from a UK rhinoplasty site.

In choosing a model we also knew what traits were desirable for our advertisements to attract the desired customers. For print modeling (e.g., catalogs and editorials—the type we needed to hire, in contrast to models needed for catwalks and television) the desired traits were very specific. The proper height was between 5’8″ and 5’10,” and the typical measurements was: bust 32″-34″, hips 33″-35″, and waist 22″-24″. The face traits were also critical. These included facial symmetry, high cheekbones, eyes that emerge, perfect teeth (no gaps, even small ones, no crooked or chipped teeth), defined lips, a Nubian nose (one  characterized by a perfectly straight bridge that lacks any curves or bends), and smooth skin free of visible blemishes. It is a rare woman (or man) who has all, or even most, of the desirable traits—something I learned when working with modeling agencies. Few girls that applied for modeling work qualified.

Research on facial preferences has constantly found widespread agreement among raters.[i] One technique is to have subjects rate the attractiveness from most to least attractive of young adults based on face pictures. When all the pictures were of white males, and another set was white females, the 53 male subjects ratings produced 92 percent agreement among the raters. Likewise, using female ratings, 94 percent agreement was reached. When pictures of young black males and another set of young black females were rated both by whites and blacks, again high (87 percent) agreement for both white male and female raters and black male and female raters. When blacks were given the same set of black males and females to rate, 95 percent agreement was produced. In short, widespread agreement of beauty exists both among males and females and this agreement exists among different people groups. (Note: all of the subjects in the pictures were Westerners as were all of the raters.) Replication of the study in different cultures will likely produce similar results.[ii]

An ancient Egyptian women painted on the wall of a tomb. Note the Nubian nose.

When I was studying the topic of sexual selection this fact was obvious. If sexual selection was true, after what Darwinists claim was 200,000 years of modern human history on Earth, why do so few women qualify today? People have had 200,000 years of practice with sexual selection to reward with survival the traits that they find attractive. A study of ancient Egyptian persons depicted in paintings and statues finds the same traits were valued then as now.

One reason, as I stressed in teaching ‘marriage and the family’ classes, was that very few people select a mate; most women are forced to settle for a mate.[6] These problems, and others, are why three main theories exist about how sexual selection actually works, all of them problematic.

Furthermore, one of the most important factors in selecting a mate has little to do with sexual attraction, namely propinquity. The author of a book for women on finding a “good enough” man says,

Propinquity, or distance in space, is one of the most influential factors in narrowing the pool of potential mates. Although we have good intuitions about the importance of propinquity, its role in mate selection is typically underappreciated.”[7]

Most of the factors that are part of the attraction package are more relevant to humans than animals. The authors of a book on human bonding call sexual selection an oversimplification based on questionable behaviors of animals. They note that an

advantage in researching humans is we can ask humans why they selected a certain person as a mate. For animal we have to guess or assume. One exception is we can measure both propinquity (physical proximity) and the pool of potential mates, both which are important factors in mate selection. These, and many similar factors, all greatly complicate Darwin’s over-simplified sexual selection theory.

A modern Egyptian women. Note the Nubian nose.


Darwin’s sexual selection theory, while seeming logical and sensible in simplistic cases (e.g., when the colorful plumage of song birds is used), fails in real life, and there are many exceptions; ravens, crows and vultures are just as successful as peacocks. When using more realistic examples, the theory breaks down, or, at least, is far more complex. Although sexual selection may have a minor role in affecting the frequency of a trait, it has little relevance to the problem of explaining the origin of the trait. Evolutionists appeal to mutation for this explanation which, of course, fails because most mutations are nearly neutral or deleterious.

See also my earlier article about sexual selection (15 March 2021).


[1] Bergman, Jerry. Sexual Selection Fails to Explain Beauty. https://crev.info/2021/03/sexual-selection-fails-to-explain-beauty/, 2021.

[2] DuVal, Emily, et al. Inferred Attractiveness: A generalized mechanism for sexual selection that can maintain variation in traits and preferences over time. PLoS Biology 21(10): e3002269; https://doi.org/10.1371/journal.pbio.3002269, 2023.

[3] DuVal, et al., 2023.

[4] Malakh-Pines, Ayala. Couple Burnout: Causes and Cures. Routledge, New York, NY, 1996, pp. 24, 33, 164.

[5] Ruger, Jack. Would He Be a Good Father? — The 10 Hidden Qualities Women Want in a Man. Independently published, 2019.

[6] Gottlieb, Lori. Marry Him: The Case for Settling for Mr. Good Enough. E.P. Dutton, New York, NY, 2011.

[7] Hazan, Cindy, and Mary Campa (editors). Human Bonding: The Science of Affectional Ties. Guilford Press, New York, NY, 2013, p. 104.

[i] Prum, Richard. The Evolution of Beauty.  New York: Doubleday. 2017.

[ii] Rumsey, Nichola and Diana Harcourt. The Psychology of Appearance. New York: Open University Press. pp. 4-5.

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 1,800 college libraries in 27 countries. So far over 80,000 copies of the 60 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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