When Rudyard Kipling first published his fables about how the camel got his hump and the rhinoceros his wrinkly folds of skin, he explained that they would lull his daughter to sleep only if they were always told “just so,” with no new variations. The “Just So Stories” have become a byword for seductively simple myths, though one of Kipling’s turns out to be half true.
The Leopard and the Ethiopian were hungry, the story goes, because the Giraffe and the Zebra had moved to a dense forest and were impossible to catch. So the Ethiopian changed his skin to a blackish brown, which allowed him to creep up on them. He also used his inky fingers to make spots on the Leopard’s coat, so that his friend could hunt stealthily, too—which now seems to be about right, minus the Ethiopian. A recent article in a biology journal approvingly quotes Kipling on the places “full of trees and bushes and stripy, speckly, patchy-blatchy shadows” where cats have patterned coats. The study matched the coloring of thirty-five species to their habitats and habits, which, together with other clues, is hard evidence that cats’ flank patterns mostly evolved through natural selection as camouflage. There are some puzzles—cheetahs have spots, though they prefer open hunting grounds—but that’s to be expected, since the footsteps of evolution can be as hard to retrace as those of a speckly leopard in the forest.
The idea of natural selection itself began as a just-so story, more than two millennia before Darwin. Darwin belatedly learned this when, a few years after the publication of “On the Origin of Species,” in 1859, a town clerk in Surrey sent him some lines of Aristotle, reporting an apparently crazy tale from Empedocles. According to Empedocles, most of the parts of animals had originally been thrown together at random: “Here sprang up many faces without necks, arms wandered without shoulders . . . and eyes strayed alone, in need of foreheads.” Yet whenever a set of parts turned out to be useful the creatures that were lucky enough to have them “survived, being organised spontaneously in a fitting way, whereas those which grew otherwise perished.” In later editions of “Origin,” Darwin added a footnote about the tale, remarking, “We here see the principle of natural selection shadowed forth.”
Today’s biologists tend to be cautious about labelling any trait an evolutionary adaptation—that is, one that spread through a population because it provided a reproductive advantage. It’s a concept that is easily abused, and often “invoked to resolve problems that do not exist,” the late George Williams, an influential evolutionary biologist, warned. When it comes to studying ourselves, though, such admonitions are hard to heed. So strong is the temptation to explain our minds by evolutionary “Just So Stories,” Stephen Jay Gould argued in 1978, that a lack of hard evidence for them is frequently overlooked (his may well have been the first pejorative use of Kipling’s term). Gould, a Harvard paleontologist and a popular-science writer, who died in 2002, was taking aim mainly at the rising ambitions of sociobiology. He had no argument with its work on bees, wasps, and ants, he said. But linking the behavior of humans to their evolutionary past was fraught with perils, not least because of the difficulty of disentangling culture and biology. Gould saw no prospect that sociobiology would achieve its grandest aim: a “reduction” of the human sciences to Darwinian theory.
Read more at The New Yorker.