Challenging Mainstream Thought About Beauty’s Big Hand in Evolution

May 30, 2017

By James Gorman

Not long ago, a physicist at Stanford posed a rhetorical question that took me by surprise.

“Why is there so much beauty?” he asked.

Beauty was not what I was thinking the world was full of when he brought it up. The physicist, Manu Prakash, was captivated by the patterns in seawater made as starfish larvae swam about. But he did put his finger on quite a puzzle: Why is there beauty? Why is there any beauty at all?

Richard O. Prum, a Yale ornithologist and evolutionary biologist, offers a partial answer in a new book, “The Evolution of Beauty: How Darwin’s Forgotten Theory of Mate Choice Shapes the Animal World — and Us.” He writes about one kind of beauty — the oh-is-he/she-hot variety — and mostly as it concerns birds, not people. And his answer is, in short: That’s what female birds like.

This won’t help with understanding the appeal of fluid dynamics or the night sky, but Dr. Prum is attempting to revive and expand on a view that Charles Darwin held, one that sounds revolutionary even now.

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4 comments on “Challenging Mainstream Thought About Beauty’s Big Hand in Evolution

  • I’ve never really understood how sexual selection can be considered a driving factor in evolution. If a peahen fancies long tails, that’s her choice, but then along comes a tiger and pulls her long-tailed offspring off low hanging branches, and inexorably the tendency to make that particular choice in mating dies out.

    I just can’t understand how sexual selection can be sustainable over time, albeit that at the point of sale, mate selection is in terms of butterflies in the stomach etc.: surely survival of the fittest must prevail, part of that package being selection of the fittest sexual selection instincts in females. The randy, roaming blade will always have his day, but his offspring will be eaten up by predators, until the instinct to choose his kind is bred out of the females.

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  • Hi eejit [#1],

    As I understand sexual selection you’re right, but only up to a point.

    The most important thing about sexual selection is that it’s about female choice. Females are limited in the total offspring they can have, while males – as long as they remain capable – may have potentially close to unlimited number of offspring.

    If it is true that a trait that arose in a species that attracted many of the opposite sex but was also deleterious to survival rates then, yes, that would tend to ensure that those individuals with the trait died before reproducing. In addition it would also tend to reduce the numbers in the population who’s mothers had fancied that trait – thus reducing the number of the species who fancy that trait. It is the combination of both the reduction of offspring from males with the trait and of offspring from females that fancied the trait that reduces the occurrence of the trait in the overall population.

    Females need to be fussier. In most species that use sexual reproduction, us humans included (even though modern living helps to level the field quite a lot) Females must expend more time and energy on nursing and gestation (and/or costly egg production). It therefore pays females big dividends to be choosy. But how to choose?

    Males do not need to be so fussy, but that doesn’t let them off the hook of needing to attract females who are also fit in order to have offspring of the fittest type. They need to find and attract those females.

    The simplest answer, and the one that fits the needs of all individuals, is to select the best mate(s) in terms of their fit to the environment – just as you stated. How? Sexual selection would be a good way to choose providing there is some correlation between the traits fancied by females and environmental fitness of the males. We know, if only from our own human experience – and other evidence is not hard to find – that sexual selection works both ways. But for females it is the greater imperative, statistically speaking, and that is probably why we see more fancy male plumage than fancy female plumage, so to speak.

    Where there is a correlation between environmental fitness and female fancy then, obviously, even a quite costly male trait (antlers, peacock’s tails and so on) can become the norm. It is also argued that something like antlers is an indication of fitness if for no other reason than the male had to be highly successful, a supremely good fit, in order to be able to spend the time and energy growing that trait. This is the very opposite of the trait sexually selected, yet damaging to survival rates.

    As far as I’m aware the balance between environmental fit and sexiness is best understood using statistics. You really can have too much of a good thing and eventually a trait that is selected sexually can become deleterious if it becomes too costly (takes too long to grow or too much food, attracts predators, etc.).

    On the other hand, male shrinking violets are more often losers.

    However, if the trait can be costly, and not too costly in terms of the individual’s survival stakes, then we get runaway effects. As I understand it this is the explanation for, for example, the peacock’s tail.

    To get the best answer I suggest you search for statistics in biology.


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  • Stephen of Wimbledon #2 + eejit #1

    However, if the trait can be costly, and not too costly in terms of the individual’s survival stakes, then we get runaway effects. As I understand it this is the explanation for, for example, the peacock’s tail.

    In sexual selection, the handicap effect of the display can result in increased predation, but the fittest and most attractive males mate with so many more females that loss of a proportion of males does not stop the process. The peacock and the birds of paradise are examples of this. Of course the differential sacrifice of the more visible males, can lead to a survival of a greater proportion of females in the population, and therefore, a greater overall number of young in the population as a whole.

    Another example of a handicap being sexually attractive to females is dark manes (which can cause over heating in the sun) in male lions. – Like a champion race-horse carrying extra weight, the fittest thrive and reproduce DESPITE the handicap, hence competing better in other areas such as defending the pride and their cubs because they ARE the fittest!

    Females need to be fussier. In most species that use sexual reproduction, us humans included (even though modern living helps to level the field quite a lot) Females must expend more time and energy on nursing and gestation (and/or costly egg production). It therefore pays females big dividends to be choosy.

    This so in the examples you give, but in species where females lay large numbers of small eggs or males take a dominant role in caring for young (Sea Horses?), there can be anomalies.

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  • Hi Alan [#3],

    The sea horse is an outstanding example of the effects of female choice in sexual selection. It seems to me their story helps to bring home the lesson that both male and female are driven by the same need to make the best of survival to adulthood and reproduce and, therefore, the role of sexual selection must be most advantageous to genes – not individuals.

    Consider that the probable initial condition was: Female sea horses produced eggs and males fertilised those eggs. Clearly, if both parties now simply swim away the fertilised eggs are merely food for any number of species, both smaller and larger.

    It does not matter to the genes which parent develops a nursing instinct, so long as one of them does. The resulting broad statistical difference in survival rates will ensure the continued spread and strengthening of that trait, that nursing allele if you will, in that species’ gene pool.

    Once a parent/nursing-of-young allele arises the probability that it will find expression in both sexes rises significantly.

    Enter female sexual selection. Even if the parent/nursing allele initially found stronger and more common expression in female sea horses, male sea horses that also showed that tendency would be a beautiful thing to the females who are otherwise stuck with egg production (an order of magnitude more work than producing sperm – and potentially a survival burden – imagine carrying a large box of twenty goose eggs with you wherever you go) and more limited mating opportunities. Adding a nursing burden also potentially reduces the female lifespan and opportunities to simply survive (e.g. to swim away from predators faster).

    Under such environmental pressures the sexiness of caring fathers becomes a valuable survival trait – this sexy trait corresponds to coincident survival-of-my-genes trait. Female sea horses get more out of the deal than male sea horses, but not nearly as much as the genes of both sexes – who win big.

    The question may arise for some reader: Why have all species not evolved along similar lines, if male parenting is such a boon? Unfortunately, I do not have the time to review half the scientific literature on evolution. Sorry.

    The NYT does not exactly boost Dr. Prum’s book, I’m certainly not inclined to shell out for it. The journalist, James Gorman, appears to be from the ‘balance’ school which – as I trust we all know at this Site – is a recipe for false premises, false dichotomies, manufactured controversy, giving oxygen to loons and much more besides. For the record: Prum does not appear to be a loon. His case may have been badly presented, he may be mistaken, but he does at least appear to be sane.

    Judging from the article; Prum’s book is a timely reminder that while survival, change, environment and reproduction are the primary drivers of evolution sexual selection plays a large and important secondary role.

    This part worries me:

    Beauty [according to many] must be adaptive, or a sign of underlying qualities that are adaptive

    Neither Prum or Gorman seems inclined to consider beauty as taste. The focus on beauty … ? [late addition: Gorman does say “there’s no accounting for taste”, what a pity he didn’t follow that line of thought further].

    Pick a behavior or an ornament or a physical trait, and it is useful until proven otherwise

    Well, quite.

    That’s backward, says Dr. Prum. Take beauty. Since animals have aesthetic preferences and make choices, beauty will inevitably appear

    I am reminded of the Monty Python song.

    For those who don’t know the above is a parody of this.

    When it comes to nature we are most assuredly not short of evidence that beauty is in the eye of the beholder.

    There is no shortage of creatures who’s bodies, habits and fancies are nauseating to us. Why choose to focus on those traits of other species that just happen to be attractive to us? Why is our perspective to be lauded above those of other species – why is what we think of as beautiful ‘correct’? This is special pleading at its most obvious and idiotic.

    The fact is we are attracted by different things to slugs, wolf fish and baboons’ (think bottoms). While these things seem ugly to us – it does not necessarily undermine Prum’s point … if, that is, Gorman is presenting a skewed picture of Dr. Prum’s point.

    Unfortunately, I very much get the impression that Prum is indeed making a distinction between taste and beauty – and promoting human taste (that is: presenting the human aesthetic view) above the tastes of all other species. We are not told why.

    Beauty happens … and it should be taken as non-adaptive until proven otherwise

    I don’t know exactly what Prum means. He appears to mean that experiencing beauty, developing a taste, occur without any precursor – that personal proclivity is not merely probable, it is paramount. How does he pontificate to this position? Perhaps his printed prose presents the necessary particulars?

    I can see no reason to shift from my understanding that female choice is driven by attraction, which may begin as arbitrary even to the extent that sexual selection can make harmful choices (as eejit outlines, #1), and yet always ends with utility because: Natural Selection.

    Like the sea horses humans also tend to generate fathers that care for offspring. Before anyone writes in to tell a tale of woe about a less-than-ideal father, I feel I should recall that we’re discussing probabilities in a population, not individual cases.

    Compared to those species closest to us – the other great apes – human fathers tend to be much closer to the sea horse model of parent. With divorce rates increasing, doubly so.

    It is my understanding from reading the NYT article that Dr. Prum extrapolates from this to propose that many human traits are the result of human female choice over many generations.

    If Dr. Prum presents evidence from studies of humans, Dr. Prum is about to set the World alight.

    I’m prepared to simply wait and see.


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