The Canon (32 page)

Among the examples that advocates often cite to illustrate the irreducible complexity of life's foundational widgetry are the tiny hairlike cilia by which paramecia and bacteria propel themselves through the water; the daisy-chain pathway of proteins that conveys light signals from the eye to the brain; and the intricate blood-clotting mechanism that keeps us from hemorrhaging uncontrollably with every nick of an envelope edge. In each case, multiple proteins cohere into unity and act with patriotic fealty, one nation, indivisible. If you destroy any one of the sixty or so proteins of which a paramecium's cilium is constructed, the hair doesn't beat more weakly or slowly than before. It cannot beat at all, and the protozoan isn't goin'. The clotting response that comes to our rescue when we fumble a morning shave is a tightly choreographed cascade of ten distinct protein "factors." If only one of those factors is defused by an inherited genetic mutation, you can end up with hemophilia, or "bleeder's disease," whereby the slightest injury can kill you. How can something as complex and essential to survival as the clotting
reaction possibly have evolved through clunky, mincing Darwinian mechanisms, Behe wonders, and the gradual plunking of one Lego piece onto another, when a defect in just a single step brings the entire business to a standstill—or, in the case of blood, to
not
stand still?

If the fundamental modules of the cell and of our biochemistry are irreducibly complex, Behe continues, and if they cannot be explained as the fruit of conventional evolutionary forces as we understand them, and if in fact they look to be the miniature set pieces of an immortal genius, an infinitely scientifically notated Leonardo, why rule out the possibility that ... they just might be? Why not leave room, at the very base of life, for the contributions of an intelligent designer? If ordinary science fails to account for something as extraordinary as the sensation of light on the eye, how scientific is it to shut one's eyes to alternative views and deeper truths, and the chance that not everything shakes out right just because? "The contemporary argument for intelligent design is based on physical evidence and a straightforward application of logic," Behe insists. "In the absence of any convincing nondesign explanation, we are justified in thinking that real intelligent design was involved in life."

ID promoters are careful not to say who or what their posited designer may be, nor whether it's a he or a she or a S/He or an anonymous corporation in Delaware. "Intelligent design itself says nothing about the religious concept of a creator," Behe writes. For many scientists, the disavowal rings disingenuous. Behe's appeal is not really for greater fairness and open-mindedness, or a request that scientists delve more deeply and rigorously into the molecular basis of life than they have to date, conceiving more imaginative experiments, redoubling their efforts to find the perfect controls. The basic message of the designer school is, Sorry, folks, there's nothing more to be done. In the biology of molecules and cells, we've reached the limits of what science can tell us. We've reached a point of irreducible complexity, and if you can't reduce a complex object to simpler and more manageable parts, well, then, you can't do much with it, can you. Science requires some degree of reductionism, some picking apart and focusing on one or two variables at a time. But if natural selection supposedly couldn't concoct a clotting cascade piece by piece, what hope is there for science to trace it methodically back to the start?

Not only are molecular scientists unwilling to throw up their hands at any problem, and say, "Oy, it's too complicated! I've never seen anything so irreducibly complicated! How about if we just toss our lab notebooks in the autoclave, invoke the 'supernatural intervention'
clause, and duck out for some fajitas and beer?" Scientists, as a group, are far too competitive and hardworking to say they can't do more when there obviously is so much more to be done. They also argue that the specific molecular assemblages and protein cascades cited by intelligent design advocates as being irreducibly complex and resistant to a Darwinian analysis can, with only moderate exertion, be disassembled into manageable subunits and those components explained as the products of natural selection. In
Finding Darwin's God: A Scientist's Search for Common Ground Between God and Evolution,
Kenneth Miller, a professor of biology at Brown University in Rhode Island, deconstructs many of ID's oft proffered instances of irreducible complexity. Among the most vivid is his vivisection of the choreography of blood clotting. He describes the step-by-step reactions that culminate in a clot: how trauma to the body's surface stimulates a succession of enzymes, or factors, circulating in the blood, each of them designated by a Roman numeral—for example, factor VIII, factor IX, factor X; and how the activation of one factor is contingent on the arousal of all the Roman soldiers preceding it; and how, at each node of the cascade, the strength of the biochemical signal is ramped up a millionfold; and how, finally, factor X bugles out a riotous reveille to an enzyme called thrombin, which clips little protective side chains off a ropy protein called fibrinogen, making the protein sticky. The newly gluey fibrinogens quickly ball together, and you've got your clot.

Miller admits that the scheme is intricate, a "Rube Goldberg machine," and that "if we take away any part of this system, we're in trouble." Medical geneticists have identified diseases stemming from mutations in just about every one of the factors in the clotting pathway, and they are all severe disorders. "No doubt about it. Clotting is an essential function, and it's not something to be messed with," Miller writes. "But does this also mean that it could not have evolved? Not at all."

As far as we know, Miller explains, the only animals that rely on a network of protein reactions to clot blood are vertebrates—we backboned mammals, birds, reptiles, amphibians, and fish—and some arthropods, particularly big, hard-shelled species like lobsters and crabs. But that doesn't mean a worm or a starfish will simply bleed to death if a blood vessel is severed. Creatures without clotting proteins rely instead on "sticky" white cells circulating in their bloodstream to patch them up. In the event of an injury, the sticky cells will cling to any proteins, like collagens, that jut out from the surface of the exposed skin; over a few minutes' time, enough white cells will have accreted at the gash site to form a plug that blocks further blood loss. Compared to the
speed and elegance with which our clotting proteins operate, the sticky-cell Band-Aid approach is crude and slow. It can work only in creatures with relatively low blood pressure, which is what most invertebrates happen to have. Nevertheless, Miller argues, "It's exactly the kind of 'imperfect and simple' system that Darwin regarded as a starting point for evolution."

Lest you think even the invertebrate's simple system is too intricate to ascribe to evolutionary forces, Miller again demurs. Those white cells serve a variety of purposes other than clotting, including nutrient delivery. Imagine a blood vessel springing a leak, Miller suggests, and imagine that a few of these white cells have randomly acquired a mutation that make them sticky when exposed to the ragged, fibrous matrix of ruptured dermis. "Any change ... in the white cells that made them stick, even just a little bit, to that foreign matrix of tissue proteins," he writes, "would be favored by natural selection because it would help to seal leaks." In other words, a random mutation that happened to lend the white cells of some ancestral worm or sea urchin a touch of Velcro would help turn current bleeder into future breeder, and so the mutation would be selected for and spread through the population, and, 'sblood! The rudiments of a clotting system are born.

Our vertebrate clotting mechanism relies on blood proteins rather than on whole cells to make clots, but still, the same sanguine logic applies. The protein factors that thicken our blood are very similar to proteins found in the pancreas and other organs that have nothing to do with clotting but instead clip and splice a variety of biochemical signals. Clipping and splicing, though, is precisely the sort of seamstressing skill needed to cross-link blood at a crisis point and bar its hasty departure. By all appearances, our clotting proteins were recruited from preexisting ranks of more generalized processing enzymes, and the genes encoding the processing proteins duplicated to enlarge the talent pool. Gradually, a number of these processors, these so-called serine proteases, were committed to the task of clotting, their reflexes honed, their internal signaling network tightened and amplified and made mutually, obligately symbiotic, the fate and force of each bound up with the rest. Today, clotting is like professional baseball. Just as the Yankees can't play with an eight-person team, so the loss of just one clotting factor can threaten your life, knock you out of the game. The current interdependency of our clotting network accounts for its extraordinary speed and vigor, but that doesn't mean it was ever thus, or can be only thus. "Blood clotting is not an all-or-none phenomenon," writes Miller. "Like any complex system, it can begin to evolve, imperfect and simple, from
the basic materials of blood and tissue." A sea urchin makes do with its simple white cells, and two kids with a ball can play catch in the park.

We don't know how life began. We don't know if it was physically inevitable, given Earth's geochemistry and the sun's generosity, and we certainly don't know if it was in any way spiritually inspired—an expression of divine love, or of cosmic curiosity, the universe's desire to understand itself. We don't know what the first life forms looked like or how they behaved. They might have been made of ribonucleic acid, RNA, or of proteins, or of molecules as yet undiscovered and unaccused. We don't know exactly when, after the formation of Earth 4.5 billion years ago, life first arose. It might well have been quite early in our planet's history. Harold Urey and Stanley Miller of the University of Chicago won international fame in the 1950s when they sought to recapitulate in the laboratory the conditions of early Earth and managed to generate amino acids, the building blocks of proteins. Miller was once asked to speculate on how long it might have taken life to originate. "A decade is probably too short, and so is a century," he replied. "But ten or a hundred thousand years seems OK, and if you can't do it in a million years, you probably can't do it at all." The operative verb in the above passage, however, is "speculate." The fossil evidence for early life is woefully, chasmically gapped. Whatever the biochemical nature of the matriarchal molecules that first managed to replicate themselves, they certainly had no hard parts, nothing for the sedimentary archives. Even after the self-copying chemicals succeeded in sealing themselves off from their surroundings, each one mapping out the boundary between me and not-me with a springy, lipidic membrane slicker and declaring itself a cell, still the young life gave no thought to tomorrow.

However life got started, one thing is clear. Life so loved being alive that it has never, since its sputtering start, for a moment ceased to live. Through the billions of years since the first cells arose, chubby bubbles enclosing the code for budding off more bubbles, life has carried on. The cipher of life, the text written in the nucleic phrases of DNA and RNA, is a universal code. Every living creature owns a piece of it. Every parasitic, periliving, propagandizing virus owns a piece of it. There is no other way of saying I'm alive but through the phonemes of nucleic acids. Had life arisen more than once, had its origins been polyphyletic rather than monophyletic, we'd see a multiplicity of codes, a selection of biochemical instructions for growth and maintenance. Yet we do not. We look at cells from creatures living on the ocean floor, 8,000 feet below the ocean surface, basking in the boiling plumes that seethe
up through hydrothermal vents, and we see DNA. We pry open bacteria trapped in polar ice for more than a million years, and we see DNA. Species arise, multiply, diversify, and die, but DNA survives—if not in the spiny
Hallucigenia
of the Cambrian era, with its seven sets of clawed tentacles fit for scavenging the ocean floor, then in the predatory lungfish,
Dipterus,
of the Devonian age; if not in trilobites, then in pterodactyls; if not in dodos, then in Lewis Carroll. The timeline of life is segmented by major mass extinctions and minor mass extinctions, and in the worst of the die-offs, huge phyletic hanks were yanked off Earth, and the ranks of the vanquished outnumbered the hangers-on by a ratio of nine-plus to under one. No matter. DNA just kept repeating itself, over and under, somersaulting somewhere, in some cell, reading itself backward—AND never running dry.

Gunter Blobel, a cell biologist at Rockefeller University, Nobel laureate, and fair grist for a limerick, sees the plain splendor in life's unbroken tenure. "When it comes right down to it, you are not twenty or thirty or forty years old," he said. "You are 3.5 billion years old. Some people may say how terrible it is, this idea that we come from monkeys. Well, it's worse than that—or better, depending on your perspective. We come from cells from 3.5 billion years ago.

"There is this tremendous thread of life that goes back to when the first cells arose, and that will continue on after any of us die as individuals," he said. "It's continuous life, and continuous cell division, and we are all an extension of that continuity. Reincarnation and similar themes are poetic representations of biological reality."

If you want to see yourself as you really are, or as your ancestors were, or as your descendants will be, Blobel said, forget about the mirror. Crack open the cell and take a look inside.

E
VERY NIGHT BEFORE
I go to bed, I grimly wage war in my mouth. First I floss, using three distinct products: normal slippery floss for most of the teeth, extrafine "floss on a stick" to get at the cramped back teeth, and the creepy concatenation of stiff and fluffy segments called "superfloss" for digging under the crowns and bridges. Then I deploy my plaque-removing, gum-massaging, erotically styled electronic toothbrush and brush for two minutes, longer if I decide to start folding laundry with my spare hand. Finally I rinse with a generous jigger of Listerine, swishing it cheek to cheek, round and round, the Bronx is up and the Battery's down, until all buccal and gingival decks have been swabbed with firewater, and I am free to spit.