IT AIN’T NECESSARILY SO
How much do evolutionary stories reveal about the mind?
BY ANTHONY GOTTLIEB
SEPTEMBER 17, 2012
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.
Exactly how our mental traits became established makes no practical difference.
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. This was no straw man. The previous year, Robert Trivers, a founder of the discipline, told Time that, “sooner or later, political science, law, economics, psychology, psychiatry, and anthropology will all be branches of sociobiology.” The sociobiologists believed that the concept of natural selection was a key that would unlock all the sciences of man, by revealing the evolutionary origins of behavior.
The dream has not died. “Homo Mysterious: Evolutionary Puzzles of Human Nature” (Oxford), a new book by David Barash, a professor of psychology and biology at the University of Washington, Seattle, inadvertently illustrates how just-so stories about humanity remain strikingly oversold. As Barash works through the common evolutionary speculations about our sexual behavior, mental abilities, religion, and art, he shows how far we still are from knowing how to talk about the evolution of the mind.
Evolutionary psychologists are not as imperialist in their ambitions as their sociobiologist forebears of the nineteen-seventies, but they tend to be no less hubristic in their claims. An evolutionary perspective “has profound implications for applied disciplines such as law, medicine, business and education,” Douglas Kenrick, of Arizona State University, writes in his recent book “Sex, Murder and the Meaning of Life.” The latest edition of a leading textbook, “Evolutionary Psychology: The New Science of the Mind,” by David Buss, of the University of Texas at Austin, announces that an evolutionary approach can integrate the disparate branches of psychology, and is “beginning to transform” the study of the arts, religion, economics, and sociology.
There are plenty of factions in this newish science of the mind. The most influential sprang up in the nineteen-eighties at the University of California, Santa Barbara, was popularized in books by Steven Pinker and others in the nineteen-nineties, and has largely won over science reporters. It focusses on the challenges our ancestors faced when they were hunter-gatherers on the African savanna in the Pleistocene era (between approximately 1.7 million and ten thousand years ago), and it has a snappy slogan: “Our modern skulls house a Stone Age mind.” This mind is regarded as a set of software modules that were written by natural selection and now constitute a universal human nature. We are, in short, all running apps from Fred Flintstone’s not-very-smartphone. Work out what those apps are—so the theory goes—and you will see what the mind was designed to do.
Designed? The coup of natural selection was to explain how nature appears to be designed when in fact it is not, so that a leopard does not need an Ethiopian (or a God) to get his spots. Mostly, it doesn’t matter when biologists speak figuratively of design in nature, or the “purpose” for which something evolved. This is useful shorthand, as long as it’s understood that no forward planning or blueprints are involved. But that caveat is often forgotten when we’re talking about the “design” of our minds or our behavior.
Barash writes that “the brain’s purpose is to direct our internal organs and our external behavior in a way that maximizes our evolutionary success.” That sounds straightforward enough. The trouble is that evolution has to make compromises, since it must work with the materials at hand, often while trying to solve several challenges at once. Any trait or organ may therefore be something of a botch, from the perspective of natural selection, even if the creature as a whole was the best job that could be done in the circumstances. If nature always stuck to simple plans, it would be easier to track the paths of evolution, but nature does not have that luxury.
In theory, if you did manage to trace how the brain was shaped by natural selection, you might shed some light on how the mind works. But you don’t have to know about the evolution of an organ in order to understand it. The heart is just as much a product of evolution as the brain, yet William Harvey figured out how it works two centuries before natural selection was discovered. Neither of the most solid post-Darwinian accounts of mental mechanisms—Noam Chomsky’s work on language and David Marr’s on vision—drew on evolutionary stories.
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