#923 - Matt Ridley - Why Evolution Favours Beauty Over Survival

Darwin's theory of sexual selection, a process distinct from natural selection focusing on mate choice for non-survival traits, initially received significant criticism and ridicule from contemporaries due to Victorian attitudes.

Sexual Selection: Darwin's Distinct Evolutionary Process Where Mates Are Chosen For Non-survival Traits

Matt Ridley introduces Darwin's idea of sexual selection as an essential evolutionary process that facilitates a significant amount of change. Darwin conjectured that, much like humans selectively breed animals for certain traits, female animals could select mates for ornamental traits over many generations. Darwin floated the idea that birds, second to humans, have an aesthetic appreciation for beauty and that female birds may choose males based on aesthetics, likening it to human appreciation.

Darwin Suggested Females Select Mates by Ornamental Traits, Similar to Human Selective Breeding

Ridley references Darwin's earlier editions of "The Origin of Species" where Darwin discussed sexual selection. He suggested females preferring visually appealing males would be akin to human efforts in selective breeding, like those seen in bantams. Ridley reflects on Darwin's comparison between human and avian aesthetic appreciation.

Darwin's Idea Of Female Birds Selecting Mates Based On Aesthetics Was Ridiculed and Rejected by Contemporaries

However, Darwin's theories, especially that female birds could make aesthetic choices, were rejected by his contemporaries. Ridley mentions Darwin's fascination with the Argus pheasant, known for its wing feathers resembling three-dimensional optical illusions, intended for visual appeal. Critics like Wood scoffed at the idea that birds with small brains could possess an aesthetic sense capable of such appreciation. Influential contemporaries, such as Wallace, Huxley, and Spencer, sided with these criticisms, showing a prevailing aversion to Darwin's concept. During a dispute with Wallace, Darwin's views, which did not regard female birds' brown coloration as camouflage, were contested, with Wallace's traditional views on natural selection being more popular.

Victorian Attitudes and Negative Reaction to Darwin's Sexual Selection Theory

Victorian discomfort with sexual matters, particularly female sexual agency, led to a negative reception of Darwin's ideas. The scientific commu ...

Matt Ridley delves into the world of birds, exploring how sexual selection favors the development of elaborate and often survival-hindering traits.

Sexual Selection in Birds Creates Survival-Hindering Traits

Sexual selection can drive the evolution of extravagant traits such as blooming feathers and elaborate mating dances, even at the expense of survival.

Why Evolve Costly Traits Over Purely Functional Ones?

Ridley points out the enigma of sexual selection: it favors traits like the peacock's opulent tail or the unique traits of the Bulwer's pheasant, which seem to hinder survival. Sexual selection often prioritizes eye-catching and energy-intensive characteristics over purely functional ones. Birds, including bowerbirds and birds of paradise, may grow and display features that take a lot of energy to maintain and might even impede their survival chances.

Sexual Selection Rapidly Drives Species-Defining Evolutionary Changes

Sexual selection not only produces these costly traits but also propels rapid evolutionary changes. Ridley refers to the Great Snipe to illustrate a potential runaway selection process—a phenomenon where extravagant traits develop quickly within a short evolutionary timeframe. Vibrant plumage and competitive behaviors, as seen in species like black grouse, though detrimental to male survival, still emerge through this intense selective pressure.

The club-winged mannequin is used as an example, with modifications in its wing bones to create unique noises for mating, emphasizing the creative force of sexual selection in bird evolution. Ridley discusses how sexual selection favors pure colors and specific frequencies in birds' songs, which may be more conspicuous, and thus selected for, despite the risk.

The paradoxical nature of these behaviors is considered in the context of the "lek paradox," which posits that choosiness among females leads to reduced genetic diversity. This in turn raises the question of why such selectivity continues when there's less genetic variability among viable males.

Ridley comments on an arms race in sexual traits potentially leading to increased extinction vulnerability, as these species invest more in sexual displays than practical survival efforts. The idea is reinforced by contrasting red grouse, which invest effort in offspring care, with black grouse, which, due to focusing on mat ...

Matt Ridley explores the concept of sexual selection in human evolution and behavior by drawing parallels to the mating behaviors and traits found in birds.

Sexual Selection in Birds and Human Evolution Parallels

Humans Show Mutual Sexual Selection, Unlike Skewed Mating in Some Lekking Birds

Ridley suggests that mutual sexual selection, a process where both sexes are choosy, is prevalent in human mate selection, just as it is in certain bird species. He cites the crested auklet and the paradise shell duck as examples where both sexes choose mates based on shared criteria, such as crests or plumage color. This mutual selection contrasts with the skewed mating systems seen in some lekking birds where only one sex, usually the male, displays for the other.

Human Brain Expansion May Be Driven by Sexual Selection For Courtship-Related Cognitive Abilities Rather Than Just Survival

Ridley also suggests that the incredible expansion of the human brain might have been driven by sexual selection for cognitive traits related to courtship, rather than purely for survival reasons. He points out that the large human brain is costly in terms of energy, and its rapid increase in size over evolutionary time suggests it must provide some significant advantage. While survival on the savannah or social living may contribute to this expansion, Ridley also entertains the idea that sexual selection can favor traits like wit and artistry—similar to how a peacock's elaborate tail is favored.

Traits Like Humor, Creativity, and Verbal Dexterity May Be Sexually Selected For Attracting Mates

Ridley touches upon certain cognitive traits that may have been developed through sexual selection to attract mates. He suggests that humor, music, song, verbal dexterity, and poetic ability could serve similar purposes in humans as colorful displays and complex songs do for birds. Research by Helen Fisher supports the idea that humor is a highly valued trait in selecting a sexual partner, indicating that individuals with such skills may enjoy gr ...