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.
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.