What I refer to as the Proof-by-Design is a venerable piece of logic, lately refurbished by the creationists. One of its earliest and most influential formulations was by John Ray, an English naturalist of the seventeenth century who did pioneering work in botany and then, in 1691, published a book called The Wisdom of God Manifested in the Works of the Creation. Ray’s argument in this book was (as the title declaims) that the elaborate design of the natural world—the matching of form to function within living creatures, the harmonious intermeshing of creatures with each other—proved the necessary existence of an omnipotent, benevolent Creator. A century later Linnaeus himself (often thought of as the first hardheaded taxonomic biologist) voiced the same idea. Right up to the time of Darwin, this view of nature was cited by both naturalists and theologians as cogent evidence for the sort of avuncular, dependable God we could all love and admire. According to one version: “This perfect Unity, Order, Wisdom, and Design, by which every Individual is necessarily related to, and made a dependent Part of the Whole, necessarily supposes and implies a universal, designing Mind, an all-powerful Agent, who has contrived, adjusted, and disposed the Whole into such Order, Uniformity, concordant Beauty and Harmony, and who continues to support, govern, and direct the Whole.” Clearly the cheerful sport who wrote that sentence had never heard of Xylocaris maculipennis.
Now the same Proof-by-Design is back in fashion among creationists, brought up to date for a new post-Darwinian purpose. These days the argument is used to prove, not merely that God does exist, but also that evolution doesn’t.
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Consider the cleaner wrasse, for instance. This little fish is the hero of an article titled “Nature’s Challenges to Evolutionary Theory,” published by Duane T. Gish’s own outfit, the Institute for Creation Research. As any marine biologist knows, a cleaner wrasse makes its living by swimming into the opened mouths of much larger, predaceous fish and picking away parasites that have infested the soft mouth tissues. The bigger fish not only permit this to happen; they come to the stations where these little wrasses have set up shop and literally wait in line to be serviced. When the cleaning is done, the little fish is allowed, gratefully, to swim safely back out of the jaws of death. In the view of the ICR, this symbiotic interaction is too complex and too improbable to have arisen by evolution. “The case for creation will be evident in certain special ecological relationships like cleaning symbiosis,” we are told. “The Christian recognizes that such processes reflect the continuing care by which God faithfully upholds His creation.”
Another big favorite is the bombardier beetle. Duane T. Gish himself has been known to cite this manifestation of God’s hands-on involvement in the designing of nature. The bombardier beetle is a small coleopteran of the genus Brachinus that carries a fancy system of chemical self-defense. Inside its abdomen are two chambers, one holding certain enzymes, the other containing a gumbo of hydrogen compounds. When threatened the beetle internally mixes these two fluids, producing a hot caustic potion of benzoquinones that explodes forth, at over two hundred degrees F., from a pair of anal spigots. The spigots can be rotated voluntarily, enabling the beetle to aim its vapor blast straight into the eyes of a hungry frog. Make my day, frog. To Duane T. Gish this stalwart little insect represents nothing less than the wisdom of God manifested—directly—in the works of nature and refutes that farfetched evolutionary alternative. Dr. Gish has even publicly challenged an eminent coleopterist to explain “how an ordinary beetle could evolve into a bombardier beetle. I want to know how natural selection has done that.” The coleopterist has responded, in plausible detail, but Dr. Gish doesn’t seem to have been listening. And last year the ICR publishing house produced a children’s book titled Bomby, the Bombardier Beetle, devoted to showing that Bomby’s physiology, too clever for evolution, can only be the product of an individual act of creative ingenuity by You Know Who.
At this point I can’t help remembering a quote from the evolutionist and philosopher Yogi Berra. Jim Piersall, before stepping into the batter’s box, scratched out a talismanic cross on the dirt near home plate. Yogi said: “Why don’t you just let Him watch the game?”
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Enough frivolity. Let’s talk about bedbugs.
It can be reasonably argued that all bedbugs are disreputable. These are sly little wingless insects, with flattened bodies that allow them to hide in tiny crevices, mouthparts suited to puncturing and sucking, and a taste for protein-rich meals of blood. They are fast on their feet and sneaky; they stay out of sight during daylight. Two related families, equally unsavory in character, are together generally known by the “bedbug” label, though only a few species actually lurk among funky mattresses to stage their blood raids against humans. Other species either parasitize bats, birds, or various larger mammals, or else prey upon mites and small insects. The association with bats is especially strong, and some scientists speculate that it’s because the bedbug group developed from cave-dwelling ancestors, vermin that prowled the guano piles hunting for insect prey and then eventually transferred their attentions to the red-blooded mammals dangling above. Cimex lectularius is the most famous species, the common bedbug that has been fervently hated by mankind for hundreds of years. Back in eighteenth-century England, C. lectularius provided work for what may have been the first professional exterminators, including a family named Tiffin whose slogan was “May the Destroyers of Peace be destroyed by us, Tiffin and Son, Bug Destroyers to Her Majesty and the Royal Family.” An interesting beast with a noble history, C. lectularius, but the most remarkable thing about it is its method of copulation. This kinky procedure is known in the euphemistic scientific jargon as traumatic insemination. In language more vivid but no less precise, it’s a combination of stabbing and rape.
The male of C. lectularius is armed with a long sharp penis. Instead of linking genitals with the female, though, he uses this organ to puncture her in the abdomen. He then ejaculates into her body cavity, and the sperm travels through her bloodstream to special receptacles, where she can store it until her time of ovulation. The puncture wound heals over, and all is fine. To you and me this may sound like the worst sort of S&M, but to bedbugs it’s just a reproductive strategy that has proven successful over many generations.
Why should traumatic insemination be necessary? The answer to that, evidently, is something called the mating plug, another bizarre reproductive strategy seen among some insects, worms, reptiles, and even a few species of mammal. By means of a mating plug, composed of glutinous secretions from his own body, the male of certain species manages, after having mated with a female, to literally glue her genital tract closed. This prevents her from mating with other males, and thereby increases his own relative reproductive success. Males of some roundworm species glue the females shut, after mating, in exactly this way. So do males among ground squirrels and moles. The traumatic insemination practiced by C. lectularius, biologists guess, arose as a way of circumventing that sort of mating plug.
But hang on, it goes further. Now we come to the variant practiced by Xylocaris maculipennis. This libertine creature (for news of which I am indebted to a fascinating new book called A Natural History of Sex by the Canadian biologist Adrian Forsyth) is a close relative to the common bedbug, but its own special fame derives from taking traumatic insemination one step beyond. Instead of just stabbing-rape, X. maculipennis practices homosexual stabbing-rape. The males puncture and inseminate other males. In fact a male of X. maculipennis may be thus assaulted even while he is copulating with a female.
No, I am not inventing this stuff from my own depraved imagination—but if you don’t believe me and Adrian Forsyth, you can consult a monograph in the journal Science, which adds the interesting information: “After homosexual rape in the anthocorid bug Xylocaris maculipennis, the sperm of the rapist enters the vas deferens of the victim and is used by the victim during copulation.” The punctured male serves as a proxy, in other words, a genetic courier, deliveri
ng the sperm of his attacker on to the next female with whom he himself mates.
To an evolutionist, that bit of genetic advantage for the rapist might explain why such behavior exists. To a creationist, though, the whole subject must be inconvenient. Unlike the world’s bombardier beetles and cleaner wrasses, X. maculipennis would seem to lend itself poorly to the Proof-by-Design.
The same ICR publishing house that brought us Bomby has served (by one account) as distributor of a tract titled “God’s Plan for Insects”—and for that matter another called “Unhappy Gays”—but I strongly doubt that either of those comes to grips with the phenomenon of homosexual rape among bedbugs. If X. maculipennis is another instance of God’s wisdom made manifest in the works of creation, I suspect that the sort of god manifested is not the one Duane T. Gish wants.
My own instinct is to agree with Yogi Berra. If God does exist, He or She is probably patient enough to take the long view.
STALKING THE GENTLE PIRANHA
An Intimate Link Between Amazon Fishes and Trees
To get there you follow the Rio Aguarico downstream out of the Andes, past a petroleum boom town called Lago Agrio where the vultures congregate by hundreds over the municipal dump, and when the last cruising vulture disappears from view behind forest canopy at a bend in the river, you will find yourself surrounded by unspoiled Amazon jungle. The oil companies and the timber cutters and the would-be cattle barons haven’t gotten quite this far, quite yet. In the treetops will be toucans and monkeys; on a snag near the bank you might, with luck, see a basking anaconda. To go where you are headed you will be traveling, of necessity, by dugout canoe. If it happens to be a long sturdy log of a boat with a 55-horse Evinrude mounted on the rear, the downriver leg of the journey will take only a couple of days. The Rio Aguarico is a broad shallow river that flows caramel-brown with suspended sediment—same color and consistency as the upper Missouri during spring runoff—but the Zabalo, its tributary, is narrow and deep and black. The blackness signals dissolved acids, steeped from rotting vegetation or leached from soils in the swampy lowland forest that the Zabalo, so slowly, drains. The mouth of the Zabalo is where your real adventure begins. You turn there and ease off on the Evinrude, heading upstream through a winding jungle tunnel like Marlow in search of Kurtz. Except that you yourself are merely in search of a fish dinner.
The idea is that the diner will be you and the role of entree will fall to the fish, though the reverse is also a possibility. This little blackwater stream, the Zabalo, is full of eager piranha.
Your guide, if he is a good one, will inform you that the Zabalo is no place for a noontime swim. Better to wait until you are back on the Aguarico, where the worst to expect is that you might step on a stingray in the shallows. For that matter, today on the Zabalo you’ll want to refrain from so much as dangling a hand overboard.
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Our own guide for the trip was a young man named Randy Borman, and he was a very good one. The son of missionary parents from the U.S., he had been raised in a small Cofan Indian village just downriver from Lago Agrio, where he blossomed into the Huckleberry Finn of the upper Amazon. He was fluent in the Cofan language, adept in their traditional skills of jungle subsistence, and pragmatically grateful for that Evinrude at the back of his forty-foot dugout. He had just enough American hellion in him to drive the canoe like it was a souped-up ’59 Dodge. As the Zabalo narrowed down tighter, and our passage upstream seemed blocked by fallen trees that lay floating across the channel, Randy would merely back the canoe off to a distance, then crank up his outboard to full throttle and charge ahead, planing out, vaulting the boat and a dozen white-knuckled passengers over each log like it was a water-ski jump at Coral Gables. He made it look easy, he even made it look sensible—but if Randy hadn’t lifted his propeller clear at just the right moment, we would have been paddling home with palm branches.
Finally came a log barrier too high for even the most reckless canoe jockey, so we made a lunch camp there on the bank. Hand lines were brought out, as well as a couple of fishhooks roughly the same size and gauge as the bend on a coat hanger. Randy balanced his way barefoot out on the barrier log to a spot in midstream, two feet above the blackwater surface of the Zabalo. He was joined there by his compadre Lorenzo, a shy Cofan man who wore a red feather through his nasal septum on formal occasions and a baseball cap reading “Oklahoma Sooners” when he was in mufti. Lorenzo was chief petty officer on this voyage, and a master of Amazon hand-line fishing. Then those two were joined on the balance-beam log by me, an incurable fool for angling of any sort.
The bait of choice was large chunks of hard salami. It released savory oils into the water and if you gave it a bit of action—some twitches and jerks, like the spasms of a small wounded fish—all the better. The first piranha to strike bit the hook in half.
So far this was not much like casting a dry fly to snooty trout on a Montana spring creek. My own touch was slow and inept. In truth, I was preoccupied with keeping my balance on that log—to set the hook on a fish and then somersault backward into the Zabalo would have seemed a hollow triumph. Lorenzo and Randy knew their craft, though, and before long they had hauled in three lunker piranha, each one as large as a flattened football, each one snapping its jaws maniacally at every finger or toe that came near. After three fish like that in ten minutes, I tiptoed carefully back to dry land.
That evening, along with our stewed caiman, we ate roast piranha. They were bony but delicious. I saved the lower jaw from one of those fish, and it sits here on the desk before me now. The teeth are pyramidal, each with a sharp point and a razor-like cutting edge. Perfect for clipping away mouthfuls of flesh from the side of a fish or a mammal—and perhaps, as we’ll see, surprisingly well suited to another function too.
I tell this whole story because several matters of science underlie it—the least interesting of which is that piranha, as advertised, can be dangerous little creatures with an eclectic palate for meat. I knew that before seeing it so vividly demonstrated, and you know it too. More fascinating, and more significant, is the network of ecological relations connecting four separate elements of this vignette. That network of improbable connections has only lately been discovered by science. The four elements are: certain piranha species found in blackwater rivers like the Zabalo, subsistence fishermen like Lorenzo, certain tree species of the lowland jungle, and floodplain development projects like the one at Lago Agrio.
The forest and the fishes turn out to be more intimately related, in parts of Amazonia, than biologists had realized.
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For a long period each year the lowland forest throughout much of the Amazon basin is covered by floodwater, in some places up to forty feet deep. Depending upon the area, the water may remain there from two to ten months. This cycle of drastic but regular flooding is the result of geologic and meteorological conditions that are not duplicated on any other continent. The ecological consequences of that flood cycle, which has repeated itself annually over millions of years, seem also to be unique on the planet.
To begin with, a large portion of the Amazon basin is extremely flat. From the Peruvian border to the Atlantic, the river drops only about 250 feet. (In the northern Rockies, for comparison, a whitewater river might drop as far within four miles.) There are exceptions to that overall Amazon flatness, of course—most notably the Andes. North of the main trunk of the river rises another formation, a modestly elevated area known as the Guianan Shield, and to the south is a similar uplift called the Brazilian Shield. Lying in among these three zones of high ground is the great Amazon floodplain. Rainfall is prodigious throughout the entire drainage, ranging between about sixty and one hundred and twenty inches per year. In consequence, the Amazon river system contains one fifth of the total amount of river water on Earth. So much water in a rush to the sea, so much flatness, and the ineluctable result is flooding. Every year, during the wet season, roughly 30,000 square miles of the Brazilian Amazon are covered
with standing water.
This land is known to ecologists as the flooded forest, and to rural Brazilians as igapó. Brazilian fishermen, in particular, have good reason to be familiar with igapó.
Over the epochs the plant species of the flooded forest have had to adapt themselves to this regularly recurrent inundation. They now live semiaquatic lives. Seedlings, saplings, and shrubs must—and do—survive being totally submerged for months of every year. Full-grown trees resist drowning despite having their roots and lower trunks covered; some species have developed special respiratory roots that top out above the flood level, like cypress knees in a Georgia swamp. But coping with floodwater itself is not the only problem those trees face. They must also cope with seed-eating fish.
During every wet season fish in great number and variety invade the flooded forest, searching for food. They come chiefly from nutrient-poor blackwater rivers, like the Zabalo, and from other streams so impoverished of minerals and small aquatic organisms that no real food chain can be supported; they come, hungry and desperate, to feed on the seeds and fruit that fall from those igapó trees. Feasting voraciously, they build up fat reserves to help carry them through the rest of the year. In some fish species the seeds and fruit taken during flood time may account for almost their total annual sustenance. And of course these fish, like the trees, have in the passing of time adapted themselves especially to this way of life. A delicate and mutually satisfactory balance seems to have developed.
An ecologist named Michael Goulding, after two years of fieldwork along the Rio Madeira, a major Amazon tributary in western Brazil, has produced the first broad study (The Fishes and the Forest: Explorations in Amazonian Natural History) of this interrelationship in the flooded forest. The featured players in Goulding’s study are a group of fish known as the characins, a highly diversified and successful clan that numbers up to a thousand species in Amazon waters. Included among the seed-eating characins is a species called the tambaqui, one of the largest fish found in the Amazon and possibly the single most important source of protein for the region’s human population. Also included, unexpectedly, are some of the piranhas.
The Flight of the Iguana Page 4
