Hey, Good Looking!

I’m wearing a grey suit, a light blue shirt and a striped tie. I don’t particularly like to dress up, especially on a warm day. I’m seeing the first drops of sweat on my forehead, and the tie is reducing the oxygen flow to my brain, but I know that Allie, my fiancée, will like my attire.

We are late, and while she finishes putting on her make up, I’m sitting in the living room staring at my fish tank. I always enjoy watching the colorful fish – each with a unique shape, size, and color – darting around the tank in their hypnotic dances. (The fish are so beautiful; it never occurs to me to wonder why.)

Allie is finally ready; I hear the clap of her high heels. She looks stunning! Today her long blond hair is down; she is wearing a white and blue dress. Then, the question I was expecting: “How do I look?”

As a partner, I only have one possible, acceptable answer: “Beautiful!”

As a neuroscientist, I can dissect the question. What sensory information do we perceive and process when we look at someone? What are the molecular mechanisms of attraction? What do we find beautiful? Ultimately, what is beautiful?

The Evolution of Beauty by Richard Prum is a fascinating, entertaining, and provocative attempt to answer that question.

The book discusses the second of Charles Darwin’s big ideas about evolution. In 1859, Darwin published On the Origin of Species, introducing the theory of natural selection (which established that organisms pass only beneficial physical and behavioral traits to the next generation) and laying the groundwork for evolutionary biology. Less known is that in 1871 Darwin published The Descent of Man, and Selection in Relation to Sex, introducing sexual selection as a second mechanism of evolution. Unlike natural selection, sexual selection evolved primarily because beauty is pleasurable to the observer, not because beauty is correlated something beneficial such as health or fitness.

Prum – a bird-watcher since his early childhood and now professor of ornithology at Yale University – revisits the theory of sexual selection proposed by Darwin, and highlights the importance of sexual selection and female choice in shaping the evolution of birds, fish, and ultimately us. He explains how the search for beauty and sexual displays do not always improve the survival of the individual, introducing the concept of “evolutionary decadence” – an overall decrease in the ability of a “show-off” species to survive as a consequence of sexual display. According to Prum, “This might provide an explanation why many of the world’s most exquisitely beautiful and aesthetically extreme creatures are so rare.” Club-winged Manakins, for example, learned to sing with rapid movements of their wings. The development of this new skill, however, required the evolution of feathers and wing bones, as well as related muscles, that compromise flight performance and efficiency. “A handsome, reckless, die-young James Dean-type,” Prum says, “leaves more offspring than a quiet librarian who lives to be an octogenarian”.

Although animals (and probably most humans) are not aware of the importance of their aesthetic and sexual choices, we are, according to Prum, “our own designers.” He proposes, in fact, that males change and evolve to please the female’s aesthetic preferences, and thus beauty is a “co-evolutionary dance between desire and display,” with females running the show. As a consequence of mate choice, individuals are responsible for creating, defining, and shaping the most extreme forms of sexual display we see in nature.

Prum uses compelling examples to bolster his argument that beauty in nature is largely arbitrary, little more than the opportunity to be admired. As a result of the search for beauty, however, wonderful, unexpected, and fundamental evolutionary leaps can happen. The ability to fly, for example, might be the result of the search for beauty. Prum theorizes that hairs originally evolved into feathers through sexual selection. A feather, indeed, is a two-dimensional canvas that allows complex pigment patterns – they can be beautiful ornaments. In turn, as a consequence of aesthetic innovation, the animal developed planar feathers that facilitated the evolution of flight!

After exhaustively discussing birds, Prum generalizes his theories to human beings. Compelling observations of primate evolution and behavior let him propose an interesting and highly speculative hypothesis about a broad range of topics, from the female orgasm (the result of female desire and pleasure, and not necessary at all to accomplish any biological function) to the lack of a bone in the human penis (the result of female mating preference for dangling genital display). He goes on to argue that there is not necessarily something of greater value in sexual attraction beyond mere sexual attraction. Evolution is not simply about the survival of the fittest individual, but also “about charm and sensory delight in individual subjective experience.”

Though well worth reading, The Evolution of Beauty also frustrates because it appears to have been written for two different audiences – academic experts on the one hand, lay readers on the other. Especially in the first chapters, I imagine that most general readers might lose interest in the lengthy, detailed descriptions of bird displays, and stop reading an otherwise very enjoyable book. Prum tries to be as objective as possible, but he certainly has a point of view, which sometimes emerges in the strong and unpleasant tone he directs at those with whom he disagrees.

Overall, Prum is very convincing about the arbitrary origin of many of the traits females prefer in males, and vice-versa. He thus argues that Darwin’s “forgotten theory” is necessary to understand and explain evolutionary biology, and to fully understand the variety and complexity of beauty present in nature.

The Evolution of Beauty will challenge the way you might think about animal evolution; Prum’s book convinced me that beauty really evolved because of female aesthetic preferences rather than any genetic benefit. Beauty gives the opportunity to be admired, and is not necessarily an honest indicator of health and fitness. It also explained to me why on a warm day I’m wearing a tie and suit, and Allie her uncomfortable high-heeled shoes. We look beautiful!

Alessio Travaglia is a postdoctoral associate at New York University, working on mechanisms of memory formation.