The Canon (31 page)

In taking up the challenge to exploit a vigorously fortified resource, the echidna, pangolin, and giant anteater have converged on the same safecracking utensils: large, sickle-shaped claws for digging into nests; a long, sticky ribbon of a tongue for poking deep into the dugouts and lapping up hundreds of insects per probe; an elongated muzzle for precision firing of the tongue; a denuded muzzle so that ants and termites have no fur to grab on to for a counterattack; enlarged salivary glands to keep the tongue gummy and to help wash the ants down; and an ironclad stomach to withstand all the sand that accompanies every ant sampler. Horses have big teeth to endure the silica contaminants in grass roots. But with no need to chew their tiny prey before swallowing, anteaters opted to preempt dental angst and have forgone tooth eruption completely. Kent Redford, a biologist with the Wildlife Conservation
Society in the Bronx who has studied anteating animals, admits that theirs is a "weird bioplan," but one with box office legs. When you see multiple lineages independently evolving a similar morphology, he said, you've got to figure the recurrent design is the obvious choice, the most natural selection.

Convergence, camouflage, Donald Duckbill and Toucan Scam. Wherever you rummage through the emperor's phyletic cabinet of curiosities, you'll see how nonrandom, how purposeful, Darwinian evolution can seem. If much of nature looks designed, that's because it
is
designed. Not from the outside in, but from the inside throughout, on the fly, by life striving to fulfill the prophecy of itself, and to remain, at all costs and by any pathway or laugh track, here on Earth, among itself, alive. Critics of evolution complain that a purely Darwinian or "mechanistic" explanation of life consigns us to a life stripped of meaning, to a world driven by random forces, exigencies, and pointless amoralities. Gregg Easterbrook, a writer who has been described as a "liberal Christian," has posited that "the ultimate argument will be between people who believe in something larger than themselves," that is, those of deep religious faith, "and people who believe it's all an accident of chemistry." Yet this binary formulation is needlessly inflammatory and far too penurious. What is the "all" that is to be explained as "an accident of chemistry"? The all of biological diversity with which the world overbrims? To characterize life as embodying accident is highly misleading, no matter what your spiritual leanings may be. Life is the anti-accident, the most thermodynamically profligate heave-ho ever instigated and subsequently amplified, annotated, explicated, expurgated, renovated ... well, you get the idea. We don't know how life began, but even that first replication of an unknown molecule was not really an accident. It was lucky that the conditions were right for the replication to occur, perhaps, but the very act of self-copying was, in its way, a deliberative act. The inherent tautology of the definition of life—that which lives and seeks to perpetuate itself—already removes accident from the equation. Indeed, there are some origin-of-life researchers who insist that, under certain conditions, life is virtually inevitable. Are these conditions rare enough to qualify as genuine accidents of chemistry? Or do they abound throughout the universe, a consequence of hydrogen and oxygen being among the commonest of all elements, and therefore water, the fount of life, being one of the commonest of molecules? We don't know yet, but I can say that the great majority of astrophysicists are convinced that we earthlings are far from alone, a subject I'll return to in the book's final chapter.

However incidental or inevitable were life's beginnings, its efflorescence into the "all" we see around us has not been at all accidental or random. "Natural selection is about as nonrandom a force as you can imagine," said Richard Dawkins. This is not to say that natural selection has specific goals in mind, or that it has proceeded in stately forward march to engineer progressively more complex and intelligent organisms, an effort of which we, of course, are the crème flambé. Natural selection seeks only to select that life which knows best how to live, and sometimes, as the archmodernist Adolf Loos said, ornament is crime. For example, the tunicate, or sea squirt, is a mobile hunter in its larval stage and thus has a little brain to help it find prey. But on reaching maturity and attaching itself permanently to a safe niche from which it can filter-feed on whatever passes by, the sea squirt jettisons the brain it no longer requires. "Brains are great consumers of energy," writes Peter Atkins, a professor of chemistry at Oxford University, "and it is a good idea to get rid of your brain when you discover you have no further need of it."

Evolution is neither organized nor farsighted, and you wouldn't want to put it in charge of planning your company's annual board meeting, or even your kid's birthday party at Chuck E. Cheese. As biologists like to point out, evolution is a tinkerer, an ad-hocker, and a jury-rigger. It works with what it has on hand, not with what it has in mind. Some of its inventions prove elegant, while in others you can see the seams and dried glue. "The assumption often is that organisms are optimal," said Bob Full, a materials scientist at the University of California, Berkeley. "They are not. Organisms carry with them the baggage of their history, and natural selection is constrained to work with the preexisting materials inherited from an ancestor. Dolphins have not reevolved gills, no titanium has been found in tortoise shells, and you would never design a bat from scratch."

Why are posters of the Heimlich maneuver hung in every restaurant, and why is it so easy to choke on a pretzel? The evolution of human language was made possible by our larynx dropping down from its previous primate position, thereby opening up a larger air space to facilitate elaborate sound production. In addition, the position of the tongue changed. Whereas a chimpanzee's tongue is contained entirely within the mouth, the back of a human tongue forms the upper edge of the vocal tract, giving it flexibility in shaping and articulating sounds. Those twin modifications incidentally brought our food and air pathways much closer together than they had been in our prehuman ancestors, or than they are in our latter-day ape kin, with a concomitant rise in
the risk of an embarrassing and potentially fatal episode of a bite of pickle dropping into the trachea rather than the esophagus, where it belongs. By themselves, the laryngeal mutations would have been swiftly whisked from the gene pool, but throw in the novel capacity for orating, educating, obfuscating, browbeating, backstabbing, filibustering, and singing jingles in the shower for products you don't even like, and
now
you're talking.

Moreover, not every feature on a creature is the product of natural selection. Some may be residual traits that are no longer needed or functional, but that are harmless and so are not under selective pressure to be tossed off like so much tunicate cerebrum. When we are cold or alarmed, for example, we get goose bumps, which may look cute on children emerging from a pool but which don't do them nearly the good they might if the children still had fur. The reaction harks back to our pelted past, when the raising of serious body hair helped to lock in heat during the cold, or made one look bigger in confronting a foe. Other traits arise in one sex not for direct utilitarian purposes, but because they're crucial in the other sex, and the basic body plan of mammalian embryonic development happens to be bisexual. Witness the male mammal's compact, dairy-free nipples, generally the same number on him as will be found on his lactationally competent counterpart—two on a man, a male chimpanzee, a male bat; ten on a male dog and eight on a male cat.

A still greater engine of pomp, camp, and comedy, of conspicuous traits that may do nothing to increase an individual's life span and in some cases help clip it short, is the evolutionary force called sexual selection. Darwin himself described this impressive complement to natural selection and offered extensive evidence of how the need to attract a mate and thwart one's rivals can have a radical impact on an animal's profile and behavior. Even traits that seem to impede a species' capacity to escape from a predator or to fade securely into the background—the standard bequests of natural selection—will find evolutionary favor, Darwin said, if they so enhance their bearer's sexual appeal that they end up swamping the competition in the gene pool. After all, if you survive long enough to breed, and if you score handsomely, even orgiastically, in a single spring spree, who cares if you're a feather duster come summer? Your seed will do your future struttings for you. The classic illustration of sexual selection at work is the peacock's tail. A peahen is a dowdy, mostly beige bit of bird-dom, but she clearly has lurid appetites. Over many generations of peahens preferring males with ostentatious posterior plumage, peacocks have evolved tails so cumbersome that
they can scarcely flap up to the lowermost branches of a tree—presumably a potential handicap for a bird native to the land of the leopard, a famously agile climber. Nobody knows why peahens like the male tails they do. Is it something about the depth and purity of the iridescent colors that signal the male's underlying genetic worthiness? Or do the peahens attend more closely to the quantity and symmetry of dark eyespots on the plumage, spots made especially prominent against a shimmering emerald and turquoise backdrop? Could it be the capacity and willingness of the male to carry the weight and to fan it wide whenever they pass that the females find so fetching? Whatever message the tail conveys, it is one no proud peacock can afford to forgo.

The ferocious struggle not only to attract a mate but to fend off rival suitors can also leave an evolutionary cross hair to bear. Each mating season, male deer do little beyond butting their racks together, until finally the lesser racks roll, and the triumphant stacks become studs. The annual intermale joustings have placed a high premium on the possession of large, sturdy antlers that can take a beating without cracking and on multiple forking prongs for latching into a rival's rack and flipping him over. The elaboration of the stag headdress has accordingly mounted over time—and is sometimes mounted over a human hunter's mantelpiece, too. Conversely, the males of many spider species are tiny, a fraction of the size of the female. She has pressing need of her heft: to catch prey, to spin silk, to lay eggs. The he-spider has need only of speed, to reach a receptive mate in advance of all those other eight-legged wallets of sperm. But the male's slight size leaves him defenseless against the female if she's in the mood for a postnuptial snack. As ever, love hurts.

William Saletan once wryly observed in the online magazine
Slate
that evolution doubters, like any other group of organisms, can be organized taxonomically. The ancestral members of the lineage are the straight-up creationists, those who interpret Genesis literally, believe the Earth to be only 6,000 years old, and insist that all species, including people, were built by God as is,
in toto
—and that goes for Dorothy and her little dog, too. No Darwinism, no natural selection, no
Eohippus
meets
Dinohippus
and talks to Mr. Ed, no cockamamie picky peahens, no Permian period. No evolution, period.

This founding credo of hard-core creationism has been around for many, many decades—it was the stimulus for the famed Scopes monkey trial of 1925—and it shows no signs of going extinct. In recent years, biblical literalists have managed to persuade the U.S. Park Service
gift shop at the Grand Canyon to carry their coffee table book,
Grand Canyon: A Different View,
which alternates gorgeous sunset photographs with the argument that the canyon is the handiwork of Noah's flood. A lavish new Museum of Earth History in Eureka Springs, Arkansas, displays fastidiously detailed models cast from genuine fossils of
Tyrannosaurus, Thescelosaurus,
and other dinosaurs, but positions them side by side with Adam and Eve and attributes the dinosaurs' demise largely to that explanatory Zelig, the Flood.

Nevertheless, the pressures of contending with the mountains and arroyos of evidence that attest to Earth's great antiquity, and to the evolution of species through the eons, have resulted in their own speciation event. Strict creationism has given rise to new species, new attempts to undercut the reach of Darwin's theory of evolution by natural selection. Perhaps the most notorious of the derivations is intelligent design, and though the phrase is meant as a tip of the hat to a presumably divine designer, it never hurts, if you're going to start a fight, to claim the word "intelligent" for your side.

Creationists, as a rule, reject the evolutionary account of when species arose and how to understand the great galloping biological diversity on which human health and all future Sierra Club calendars depend. Creationists see nothing implausible about a museum diorama depicting dinosaurs grazing alongside woolly mammoths because they are unpersuaded by the stratification of the fossil record that would separate the animals by at least 60 million years—a figure that in any event exceeds their estimate of Earth's age by a factor of 10,000.

Advocates for the idea of intelligent design, on the other hand, are quite willing to accept the geological evidence that our planet is about 4.5 billion years old, and they concur with the mainstream view of a biological timeline that dates back several billion years. They have no quarrel with the proposition that humans arose from apelike progenitors, nor with the general capacity of whole organisms to change over time and give rise to new species. A number of the ID heavyweights are scientists, most vocally Michael J. Behe, a professor of biological sciences at Lehigh University in Bethlehem, Pennsylvania. "Intelligent design proponents," he wrote in an op-ed piece for the
New York Times,
"do not doubt that evolution occurred."

Where the ID ideologists part company with the preponderance of scientists is on the origin of the smallest components of life—our cells and the enzyme and protein "machines" that keep our cells and selves thumping. As Behe and his sympathizers see it, cells and their microcircuitry are almost too good, too well composed, too perfect, to be believed. Many of the protein complexes essential to life, they say, work only if all the parts are present and pulling their weight. Should one participant in these molecular assemblages fail, should one spring go sproing, then the entire structure collapses. In other words, when you go below the gross scale of the body, below the squishy, messy organs of the body, and get down to the fundamental units of a body, you start to encounter elegance, beauty, something they call "irreducible complexity." The protein partnerships that run the show could not have arisen gradually, they say, through random mutations and modifications of preexisting structures. The molecular components of the cell are too interdependent, too carefully arrayed, to be the product of ordinary Darwinian natural selection. Natural selection requires that intermediary stages in an evolving structure lend an advantage to their recipient over the structures that preceded them. If you're a frog that looks a tiny bit like a leaf, you'll have a tiny survival advantage over another frog that looks purely frog, and so a leafy camouflage can evolve in stepwise fashion. A slight widening of the skin on the front legs that allows an arboreal mammal to get a bit of lift as it leaps from a branch may help it escape predation, and therefore you can imagine the gradual triceps extension that leads to the winged bat. But with these molecular assemblages, the IDers insist, there's no in between. The pieces must all be in place, watches synchronized, or you get system failure. Natural selection doesn't work on complex, interdependent assemblages, they say. If draft versions of a product flop completely, they won't be selected, and you'll still be stuck up a tree.