As a child, Charles Darwin was fascinated by nature. He collected beetles avidly, and was once so determined to capture a specimen, despite having his hands full, that he placed it in his mouth to carry home. His reward was a mouthful of defensive beetle-acid, but his enthusiasm remained intact. His family estate, The Mount, near Shrewsbury, had an excellent library full of his father's natural history books, a greenhouse stocked with exotic plants, an aviary for the fancy pigeons his mother kept, and access to a bank of the River Severn. Young Charles preferred nature's sights and sounds to the rote learning of Latin at the local Shrewsbury School.
By age 23, Darwin had left Shrewsbury for South America. His round-the-world voyage on the Beagle introduced him to the astounding volume and diversity of nature's ornaments. England had passerine birds with intricate songs, and pheasants with stately colors, but nothing prepared the young naturalist for the richly ornamented flora and fauna of the tropics: iridescent humming birds visiting outlandish flowers; beetles with carapaces of gold, sapphire, and ruby; enigmatic orchids; screaming parrots; butterflies like two blue hands clapping; monkeys with red, white, black, and tan faces; exotic Brazilian fruits on market stalls. On a single day during a foray from Rio, Darwin caught no less than 68 species of beetle. His diaries record his "transports of pleasure and the "chaos of delights" inspired by the jungle's baroque extravagance—"like a view in the Arabian Nights."
Darwin wanted an explanation for this rich array of diversity. Two decades before Darwin's trip, theologians such as William Paley had argued that God ornaments the world to inspire man's wonder and devotion. Darwin may have wondered why God would put tiny golden bugs in the heart of a sparsely populated jungle, a thousand miles from the nearest church. Were nature's ornaments really for our eyes only? Between the Beagle's voyage and his notebooks of 1838, Darwin had worked out the principle of evolution by natural selection. He realized that bugs must be golden for their own purposes, not to delight our eyes or to symbolize divine providence.
Animal ornaments must have evolved for some reason, but Darwin could not see how his new theory of natural selection could account for these seemingly useless luxuries. He had seen that many animals, especially males, have colorful plumage and melodious songs. These are often complex and costly traits. They usually have no apparent use in the animals' daily routine of feeding, fleeing, and fighting. The animals do not strive to display these ornaments to humans when we appear to need some spiritual inspiration. Instead, they display their beauty to the opposite sex. Usually, males display more. Peacocks spread their tails in front of peahens. In every European city, male pigeons harass female pigeons with relentless cooing and strutting. If the females go away, the male displays stop. If the female comes back, the males start again. Why?
Once his travels had confronted Darwin with the enigma of animal ornamentation, he could never take it for granted again. After his return, it seemed to him that English gardens were awash with peacocks. Their tails kept the problem in the forefront of Darwin's mind, sometimes with nauseating effect. Darwin once confided to his son Francis that "The sight of a feather in a peacock's tail, whenever I gaze at it, makes me sick!" The peacocks seemed to mock Darwin's theory that natural selection shapes every trait to some purpose.
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