“Truth needs no colour, with his colour fix’d;
Beauty no pencil, beauty’s truth to lay;”
—William Shakespeare, Sonnet 101
Summarizing observations of phenomena that have evolved over eons is a daunting proposition, so check the video at the end of this post; and of course to the book, “The Evolution of Beauty”, that has been named the best book of the year by a number of esteemed publications.
Charles Darwin published “Origin of Species” in November 1859, where he provided cogent analyses to illustrate that organisms evolve through a process of natural selection. Alfred Wallace, Darwin’s contemporary, had arrived at a similar conclusion and papers by both Wallace and Darwin were read at the 1858 meeting of the Linnean Society. According to the Darwin Correspondence Project, Wallace and Darwin exchanged almost 200 letters discussing their findings with each other, each providing evidence for his conclusions.
In a letter to Wallace, dated 1 May 1857, Darwin writes:
“This summer will make the 20th year (!) since I opened my first-note-book, on the question how & in what way do species & varieties differ from each other.— I am now preparing my work for publication, but I find the subject so very large, that though I have written many chapters, I do not suppose I shall go to press for two years.”
As the two men continued their observations, they began to gradually diverge in opinion. In an 1869 letter, Wallace writes to Darwin regarding the upcoming publication of Darwin’s “The Descent of Man, and Selection in Relation to Sex” :
“I was delighted to see the notice in the “Academy” that you are really going to bring out your book on Man. I anticipate for it an enormous sale, and shall read it with intense interest, although I expect to find in it more to differ from than in any of your other books.”
Indeed, it is in Descent of Man that Darwin worries about apparent maladaptive features in organisms such as the peacock – why would a male have such heavy plumage? Darwin provided two possible reasons – one that has received greater press than the other. Darwin suggested that the elaborate plumage might be a mode of competing with other males, and the winner would have access to a female mate; or that the female, rather than playing a passive role, drove the process of selection based on her aesthetics of the male’s courtship display.
Over the 147 years since publication of Descent of Man (the 147th anniversary is next week, on 24 February), the second possibility that Darwin suggested, has been forgotten – that the female of the species might be the driving force in the evolution of some spectacular visual and aural displays seen in birds. Using some riveting footage that he and his colleagues have collected over the years, Professor Prum made a powerful argument in support of female choice in the evolution of beauty. What is intriguing though, is that in the process of incorporating more aesthetically pleasing characteristics there is a cost; in the case of a peacock, the cost is a smaller flight range which can translate to a limited ability to escape predators. Perhaps the most dramatic example was that of the club-winged manakin found in Ecuador – the male in this species, unlike most birds, has some solid bones in its wings that allow them to make a clicking sound when trying to attract a mate. These solid bones whose presence was revealed in a CT scan, come at a cost to efficient flight. Here’s a wonderful video demonstrating how the bird “strikes [the secondary wing feathers] together at about 107 times per second to create a buzzing sound, which is used during courtship displays.”
Thank you, Professor Prum, for a marvelous afternoon at Tilde Cafe. Those of us who aren’t evolutionary biologists have now caught a glimpse of Darwin’s second possibility – a perfect 75th cafe celebration.
The video of the afternoon follows: