Biologist Richard O. Prum, an ornithologist and evolutionary expert at Yale University (USA), is fascinated by the beauty of birds. He is especially interested in the beautiful and colorful rituals that some birds perform to choose a partner. They are really complex and refined. A good example is that of the royal argos (Argusianus grayi), a robust pheasant of Sumatra and Borneo whose males make the peacocks pale. These clear plots of the forest, peck the ground and parade in front of the females. At a peak, the animal becomes a kind of umbrella defeated by the wind and envelops the female with feathers one meter long in a dazzling dance of colors and optical illusions, under the watchful eye of the male (such as It can be seen in this video, on the left of the screen).
The most widespread evolutionary explanation for these types of behaviors is that they are like a brand that indicates how good the genes of these birds are. But Prum has something else in mind. Based on a little known theory by Charles Darwin, who published in his book “The origin of man and selection in relation to sex,” this scientist suggests that these animals simply appreciate beauty. The females of the argos enjoy this display and, over thousands of years, they have been choosing the males that best did it. Therefore, there are beautiful birds that dance together to seduce females or others that neatly decorate their plots with fungi, leaves, insect shells or fruits of different colors. Among birds, females have had the power.
The power of beauty in humans
Richard O. Prum defends these ideas in his book “The Evolution of Beauty” (attic book publishing house). And not only does it apply to birds. The author extends them to a hairless ape whose way of looking for a partner differs markedly from those of his peers: the human. Prum argues that the sexual pleasure and enjoyment that the human being experiences before and during intercourse has allowed the female’s preferences to have shaped the male body, but that, at the same time, their preferences have changed the female. All this has turned sex into a pleasurable act, complex and far from mere reproduction, with very intense orgasms and a very molded attraction for culture and personality. When talking about all this, Prum seems to overthrow some myths: that their orgasm has some hidden function, beyond pleasure, or that they are not selective when looking for a partner.
The key to these ideas is based on a conception defended by Darwin at the end of his life: that sexual ornaments are arbitrary and not necessarily linked to an adaptive advantage, that is, that allow more descendants to be left. Quite simply, certain traits are beautiful or desirable for the other sex, generate a specific sensory response, and that already has value in itself. At some point there may be a relationship between the beautiful and the adaptive, but Richard O. Prum recalls the need to prove it and not take it for granted.
The human ape
Humans are African apes, a line of old-world primates, including gibbons, orangutans, gorillas and chimpanzees. Each of their relatives has a different sexual behavior: for example, gorillas live in groups of multiple females dominated by a single male with a “silver back” and only have sex when the female is in heat. However, bonobos practice sex with many individuals in their group, without the need for jealousy, even with same-sex peers. Apart from reproduction, the sexual act is a tool with which bonobos resolve social conflicts.
Humans also have sex regardless of women’s fertility but, unlike bonobos, they are very demanding of people with whom they have relationships and “human sexuality becomes especially complicated,” writes Richard O. Prum. One of the things that explain it is that, along with the biological evolution that continues to occur today, among living humans, another cultural evolution occurs in all the populations of the planet. Over and over they are happening partly through the sexual preferences that men and women have. This choice of mutual partner shapes the appearance and behavior that both have. Consequently, there are some distinctive features that the author is reeling throughout his book.
Women are selective … men too
First, Richard O. Prum questions the idea supported by evolutionary psychology according to which, since sperm is cheap to produce and eggs are expensive, “men are sexually wasteful and women sexually shy.” He says that this stereotype very poorly reflects human behavior: neither men and women have such a different number of sexual partners in their lives, neither do they have random sexual encounters. Both are selective.
For men, this has to do with the fact that “human males make significant reproductive investments, that is, they dedicate resources, time and energy to protect, care, feed and socialize their offspring,” writes the author in “The evolution of beauty ». Therefore, “hopefully males evolve to be more selective about who they want to reproduce with.” This would differentiate them, therefore, from male birds that do not invest time or energy in their young.
Big breasts and wide hips
These male preferences have consequences on women. “The result has been the coevolution of specific female sexual traits, such as permanent breasts and a specific body shape, which are not present in any of the other apes,” writes the author. It is true that they are related to the need to give birth or to the efficient ability to store fat, but they have also evolved because of the choice of male partner. As much as to go far beyond what is necessary for survival or reproduction, such as the long and beautiful feathers of the royal argos.
For starters, while mammals’ breasts increase in size during ovulation and lactation, “human females develop larger breasts when sexual maturity begins and retain enlarged breast tissue throughout their lives.” This development of permanent breasts, an exclusive feature of human beings, “is not necessary for reproduction itself and has no natural selective advantage,” Prum says. “Rather, the existence of breasts in women is probably an aesthetic feature that has evolved due to the choice of partners by men.”
In addition, in women the fat of the buttocks accentuates the hourglass shape created by the breasts, the waist and the hips. According to Prum, there is no evidence that this specific fat distribution is related to a woman’s genetic quality or health.
Not very masculine faces
Despite the shortage of studies that analyze it, they also choose. According to the author, “there is consistent evidence that females do not prefer the more” masculine “factions, characterized by a square and prominent jaw, a broad and clear forehead, thick eyebrows and thin cheeks and lips. There are numerous studies that “have shown that women prefer intermediate facial features or even those that some researchers describe as” feminine. ” Similarly, they seem to prefer beards two days earlier than more populous and supposedly male beards.
In addition, a handful of studies show that they “usually prefer male bodies with muscles but thin, with wide shoulders and V-shaped torsos, and, on the other hand, they do not usually like the more muscular men so much.”
A big penis
Richard O. Prum argues that the human penis is another feature that has been arbitrarily selected by women, without their current attributes being adaptive. “Several aspects of human penis morphology are beyond what is necessary to achieve intercourse and fertilization.”
While a gorilla’s penis measures three centimeters or that of chimpanzee seven, “the human penis is longer (on average about fifteen centimeters in erection) and is wider than the penis of the other apes.” In addition, unlike the others, it is characterized by “a bulbous glans and a crown crest.” As if that were not enough, compared to the other primates, with the exception of the spider monkey, the human has a penis that lacks a bone inside, which is called
or penile bone.
Why would the human penis evolve in this way? Prum argues that there is no concrete adaptive advantage for this exotic penis and suggests that it has been the aesthetic preferences of women for these morphologies that have given it its shape. The reason? Sexual pleasure.
Size matters, but not so much
Nonhuman primates have a penis that disappears when it is not erect. However, the human penis hangs and does visibly, “since it evolved to be larger and longer than that of any other primate.” According to the author, this suggests that perhaps women “liked it as an exhibition feature.”
For Prum, it is likely that the rest of his features (thickness, glans, etc.) have “evolved from female preferences for male mating organs that produce greater pleasure.” This would not only be linked to observation, but also to the sensory and tactile experience of sexual interactions and intercourse.
This would lead to a preference for larger penises, compared to other primates, but not necessarily compared to other human penises. «Women’s responses to the question of whether” size matters “are very variable. And, which is also very interesting, the size of a man’s penis is also very variable, ”explains the researcher. “Is it possible that both variations are related?” He asks. As with other features, such as female breasts, «if the size of the penis is an arbitrary aesthetic feature (…) it could be highly variable and respond to a multitude of tastes, and that is what happens. For tastes, colors (or sizes) ».
Everyone can find happiness with another
Logically, the role of social interactions cannot be forgotten: “They are a vital element in how we experience sexual attraction, who we are going to have sex with and how we are going to fall in love,” writes the scientist. Consequently, “Our perceptions of sexual attractiveness change as we get to know the other person more.”
Finally, “subjective social perceptions have a greater weight in what they find attractive than physical appearance,” according to Prum. This leads to an interesting circumstance, as researchers Paul Eastwick and Lucy Hunt write: “This idiosyncrasy will reveal itself fortunate, since it allows almost everyone to have the option of establishing relationships where both parties see each other as a desirable being of unique way ».
This is a wonderful thing, as the author proposes: «It is a happy idea to think that people, in general, are designed to find social and sexual happiness with another, despite variations in physical attractiveness. “Couples value” is not an objective and universal measure: it is a relational and subjective experience ».
Choose a partner through repeated sex
The biologist emphasizes the importance of intercourse for the selection of partners in humans. “Sex offers individuals a wide and rich range of sensory stimuli that can be evaluated.” Since human sexual encounters have a low probability of leading to fertilization, and the ovulation (zeal in animals) of women is hidden, for Richard O. Prum should think “that humans have reappearance preferences.” Men and women select their partners through repeated sexual encounters.
The experience of choosing a partner is, in itself, pleasant, as even Darwin proposed. Repeated sexual encounters, the aesthetic evaluation of the cognitive, sensory and physiological experiences of the sexual act itself, transformed the mating behavior of men and women, which led to sex becoming an intense, complex and satisfying experience. It would also explain the richness of the postures during the sexual act.
“The aesthetic proposal is that sexual pleasure and female orgasm have evolved because women prefer to mate, and mate again, with men who stimulate their own pleasure,” concludes the researcher. But man is not far behind. While their own pleasure has a function closely related to ejaculation, they also enjoy very pleasant orgasms, more than is strictly necessary. Proof of this is, according to the researcher, that intercourse and human male orgasm lasts longer than that of chimpanzees or gorillas.
In addition, they do not accept any opportunity to copulate, “by avoiding some sexual opportunities in favor of others that they want more; in other words, by choosing a partner ».
Sexuality and culture
The complexity is multiplied because, apart from supposed ornaments such as the breasts or the penis, human culture plays a huge role in the choice of couple: “There is no human sexuality without culture,” says the author. For Richard O. Prum it is likely that these arbitrary cultural preferences have modulated not only behavior (such as courtship) but also “our own bodies.”
At this point, remember that “What one culture considers sexy may be subject to censorship in another.” This would explain that the feminine beauty of the classic statues is not considered attractive in today’s Western world, or that for young Mauritanians the stretch marks on the skin of women are exciting because of their rapid weight gain.
For all this, as the author concludes, “Men and women are together in this” and, probably, “the choice of mutual partner (…) has led to the refinement of orgasm in both sexes.”
Many of these ideas, which the author himself acknowledges speculative, could explain why beauty and pleasure have evolved as they have for millions of years, in creatures as different as birds or primates. And they are also an interesting explanation for the complex and rich sexual behavior of humans. .