In the Western Andes of Ecuador, small brown birds with a red crown, club-winged manakins, use their wings to sing. They open and close their wings to produce sounds resembling an electric guitar–bip, bip, WANNGG, bip, bip, WANNGG! These male birds are trying to attract female mates, who find this very type of music very alluring. This new way of singing is also an evolutionary innovation.
This evolutionary mechanism is “not an adaptation by natural selection, in which those who survive pass on their genes . . . It is sexual selection by mate choice in which individuals pass on their genes only if selected as mates.” Most biologists believe that sex appeal is an objective sign of better genes being carried through and leading to self-improvement. (Prom, 2017). But in this instance, these club-winged manakins may be headed to extinction. In choosing mates—an in birds it’s mostly the females who choose—animals make choices that can only be called aesthetic. “ (Gorman, 2017).
In 2005, high-speed video captured by biologist Kimberley Botswick showed that the bird’s wings oscillate causing the feathers to rub against each other, thicken, and resonate. “The bird songs involve more than just unusual feathers and movements. They require evolutionary changes in the shape of their bones.” (Prom, 2017). Why this is important is that bird wings are uniform among species because flight places precise demands on the design of the wing. The club-winged manakin’s wings, however, are four times wider than those of their species. Thus, they are worse at flying in order to be attractive to their sexual mates.
The wing songs not only affect the bones of the males, they also affect females with the same distorted shape as the males. Although they never sing, the females have also become less capable fliers. The effects of the sexual selection has occurred because “avian wing bones take shape early in the life of any embryo before sexual differential has begun. This prevents females from evolving a different wing-bone shape from males.” (Prom, 2017)This type of demand that sexual selection is placing on them is decreasing their capacity for survival.
This shows that natural selection does not shape everything in evolution.
Gorman, James, Challenging Mainstream Thought About Beauty’s Big Hand in Evolution. May 2017., NY Times. https://www.nytimes.com/2017/05/29/science/evolution-of-beauty-richard-prum-darwin-sexual-selection.html
Prom, Richard. Are These Birds Too Sexy to Survive? New York Times, May 2017.https://www.nytimes.com/2017/05/05/opinion/sunday/are-these-birds-too-sexy-to-survive.html
Prom, Richard. The Evolution of Beauty: How Darwin’s Forgotten Theory of Mate Choice Shapes the Animal World – and Us, Penguin Random House LLC, New York, 2017.