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Sometimes it seems there is no limit to scientific reductionism—the shrink–wrapping of creation's mysteries in scientific facts. Nothing is exempt, not even the bewildering brilliance of the autumn leaves. The changing leaves can't just be God's gorgeous decorations; they have to have a logical and practical purpose, a cause and effect. William Hamilton's so–called "leaf signal hypothesis" holds that leaves brighten in order to deter parasites. Now, as science–writer and blogger Carl Zimmer reports, a new hypothesis has emerged: the colors of the leaves are trees' way of storing up nutrients for the winter. The blazing pigments shield the leaves from the sun's ultraviolet rays as they kick photosynthesis into high gear, using the extra energy to return their nitrogen, phosphorus, and other vitamins back to the tree before they fall away and die.
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These theories are interesting, and surely worthy of serious scientific study. Beauty and bug repellent may indeed go hand–in–hand. But our disappointment at the sterile rationality of these theories is analogous to Walt Whitman's in his poem "When I Heard The Learned Astronomer." When he listens to an astronomy lecture and "the proofs, the figures, were ranged in columns before me," Whitman discovers he'd rather be standing outside, gazing in awe at the stars. Doubly troublesome, though, is the pragmatic attempt to reduce the beauty and intricacy of nature to mere evolutionary function. Through the leaf signal hypothesis, wrote the London Guardian, the changing colors of the leaves are "given a meaning by evolution" (emphasis added). Their aesthetic delight as a clue to their purpose—being brushstrokes of a master artist—is rendered irrelevant.
For a more fulfilling encounter with fall's folial show, treat yourself to Autumn: A Spiritual Biography of the Season. Sample this survey of some of the best poetry, memoir, and landscape writing that has emerged from the season, including Thoreau's essay "Autumnal Tints." "October is the month for painted leaves," he wrote. "As fruits and leaves and the day itself acquire a bright tint just before they fall, so the year nears its setting. October is its sunset sky; November the later twilight."
Susan Fenimore Cooper sees a landscape that "shows its wooded heights dyed with the glory of October, its lawns and meadows decked with colored groves, its broad and limpid waters reflecting the same bright hues." Zoologist Allen Young says the changing of the leaves is "when autumn begins to show its personality," as "its cooling brush repaints the canvas of foliage from greens to bright colors," in "summer's ebullient finale."
Equally evocative, though, are the collection's accounts of the void left by the cascading leaves as October turns to November, and rigor mortis sets in among the dull brown trees before they are whitewashed by winter. In "My November Guest," Robert Frost beholds "The desolate, deserted trees / The faded earth, the heavy sky," and says he has learned "The love of bare November days / Before the coming of the snow." Donald Culross Peattie compares this decrescendo to that of a symphony. "The leaves descend in golden glory," he writes. "And so with slow chords in imperceptible fine modulations the great music draws to its close, and when the silence comes you can scarce distinguish it from the last far–off strains of the woodwinds and the horns."
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