The Deniable Darwin.
The fossil record is incomplete, the reasoning flawed; is the theory of evolution fit to survive?
DAVID BERLINSKI JUNE 1, 1994 INTELLIGENT DESIGN.
CHARLES DARWIN presented On the Origin of Species to a disbelieving world in 1859 — three years after Clerk Maxwell had published “On Faraday’s Lines of Force,” the first of his papers on the electromagnetic field. Maxwell’s theory has by a process of absorption become part of quantum field theory, and so a part of the great canonical structure created by mathematical physics.
By contrast, the final triumph of Darwinian theory, although vividly imagined by biologists, remains, along with world peace and Esperanto, on the eschatological horizon of contemporary thought.
“It is just a matter of time,” one biologist wrote recently, reposing his faith in a receding hereafter, “before this fruitful concept comes to be accepted by the public as wholeheartedly as it has accepted the spherical earth and the sun-centered solar system.” Time, however, is what evolutionary biologists have long had, and if general acceptance has not come by now, it is hard to know when it ever will.
IN ITS most familiar, textbook form, Darwin’s theory subordinates itself to a haunting and fantastic image, one in which life on earth is represented as a tree. So graphic has this image become that some biologists have persuaded themselves they can see the flowering tree standing on a dusty plain, the mammalian twig obliterating itself by anastomosis into a reptilian branch and so backward to the amphibia and then the fish, the sturdy chordate line–our line, cosa nostra–moving by slithering stages into the still more primitive trunk of life and so downward to the single irresistible cell that from within its folded chromosomes foretold the living future.
This is nonsense, of course. That densely reticulated tree, with its lavish foliage, is an intellectual construct, one expressing the hypothesis of descent with modification.
Evolution is a process, one stretching over four billion years. It has not been observed. The past has gone to where the past inevitably goes. The future has not arrived. The present reveals only the detritus of time and chance: the fossil record, and the comparative anatomy, physiology, and biochemistry of different organisms and creatures. Like every other scientific theory, the theory of evolution lies at the end of an inferential trail.
The facts in favor of evolution are often held to be incontrovertible; prominent biologists shake their heads at the obduracy of those who would dispute them. Those facts, however, have been rather less forthcoming than evolutionary biologists might have hoped. If life progressed by an accumulation of small changes, as they say it has, the fossil record should reflect its flow, the dead stacked up in barely separated strata. But for well over 150 years, the dead have been remarkably diffident about confirming Darwin’s theory. Their bones lie suspended in the sands of time-theromorphs and therapsids and things that must have gibbered and then squeaked; but there are gaps in the graveyard, places where there should be intermediate forms but where there is nothing whatsoever instead.(1)
Before the Cambrian era, a brief 600 million years ago, very little is inscribed in the fossil record; but then, signaled by what I imagine as a spectral puff of smoke and a deafening ta-da!, an astonishing number of novel biological structures come into creation, and they come into creation at once.
Thereafter, the major transitional sequences are incomplete. Important inferences begin auspiciously, but then trail off, the ancestral connection between Eusthenopteron and Ichthyostega, for example–the great hinge between the fish and the amphibia–turning on the interpretation of small grooves within Eusthenopteron’s intercalary bones. Most species enter the evolutionary order fully formed and then depart unchanged. Where there should be evolution, there is stasis instead–the term is used by the paleontologists Stephen Jay Gould and Niles Eldredge in developing their theory of “punctuated equilibria”–with the fire alarms of change going off suddenly during a long night in which nothing happens.
The fundamental core of Darwinian doctrine, the philosopher Daniel Dennett has buoyantly affirmed, “is no longer in dispute among scientists.” Such is the party line, useful on those occasions when biologists must present a single face to their public. But it was to the dead that Darwin pointed for confirmation of his theory; the fact that paleontology does not entirely support his doctrine has been a secret of long standing among paleontologists. “The known fossil record,” Steven Stanley observes, “fails to document a single example of phyletic evolution accomplishing a major morphologic transition and hence offers no evidence that the gradualistic model can be valid.”
Small wonder, then, that when the spotlight of publicity is dimmed, evolutionary biologists evince a feral streak, Stephen Jay Gould, Niles Eldredge, Richard Dawkins, and John Maynard Smith abusing one another roundly like wrestlers grappling in the dark.
Pause for the Logician
SWIMMING IN the soundless sea, the shark has survived for millions of years, sleek as a knife blade and twice as dull. The shark is an organism wonderfully adapted to its environment. Pause. And then the bright brittle voice of logical folly intrudes: after all, it has survived for millions of years.
This exchange should be deeply embarrassing to evolutionary biologists. And yet, time and again, biologists do explain the survival of an organism by reference to its fitness and the fitness of an organism by reference to its survival, the friction between concepts kindling nothing more illuminating than the observation that some creatures have been around for a very long time. “Those individuals that have the most offspring,” writes Ernst Mayr, the distinguished zoologist, “are by definition . . . the fittest ones.” And in Evolution and the Myth of Creationism, Tim Berra states that “[f]itness in the Darwinian sense means reproductive fitness-leaving at least enough offspring to spread or sustain the species in nature.”
This is not a parody of evolutionary thinking; it is evolutionary thinking. Que sera, sera.
Evolutionary thought is suffused in general with an unwholesome glow. “The belief that an organ so perfect as the eye,” Darwin wrote, “could have been formed by natural selection is enough to stagger anyone.” It is. The problem is obvious. “What good,” Stephen Jay Gould asked dramatically, “is 5 percent of an eye?” He termed this question “excellent.”
The question, retorted the Oxford professor Richard Dawkins, the most prominent representative of ultra-Darwinians, “is not excellent at all”:
Vision that is 5 percent as good as yours or mine is very much worth having in comparison with no vision at all. And 6 percent is better than 5, 7 percent better than 6, and so on up the gradual, continuous series.
But Dawkins, replied Phillip Johnson in turn, had carelessly assumed that 5 percent of an eye would see 5 percent as well as an eye, and that is an assumption for which there is little evidence. (A professor of law at the University of California at Berkeley, Johnson has a gift for appealing to the evidence when his opponents invoke theory, and vice versa.)
Having been conducted for more than a century, exchanges of this sort may continue for centuries more; but the debate is an exercise in irrelevance. What is at work in sight is a visual system, one that involves not only the anatomical structures of the eye and forebrain, but the remarkably detailed and poorly understood algorithms required to make these structures work.
“When we examine the visual mechanism closely,” Karen K. de Valois remarked recently in Science, “although we understand much about its component parts, we fail to fathom the ways in which they fit together to produce the whole of our complex visual perception.”
These facts suggest a chastening reformulation of Gould’s “excellent” question, one adapted to reality: could a system we do not completely understand be constructed by means of a process we cannot completely specify?
The intellectually responsible answer to this question is that we do not know–we have no way of knowing. But that is not the answer evolutionary theorists accept. According to Daniel Dennett (in Darwin’s Dangerous Idea), Dawkins is “almost certainly right” to uphold the incremental view, because “Darwinism is basically on the right track.” In this, he echoes the philosopher Kim Sterenly, who is also persuaded that “something like Dawkins’s stories have got to be right” (emphasis added). After all, she asserts, “natural selection is the only possible explanation of complex adaptation.”
Dawkins himself has maintained that those who do not believe a complex biological structure may be constructed in small steps are expressing merely their own sense of “personal incredulity.” But in countering their animadversions he appeals to his own ability to believe almost anything. Commenting on the (very plausible) claim that spiders could not have acquired their web-spinning behavior by a Darwinian mechanism, Dawkins writes: “It is not impossible at all. That is what I firmly believe and I have some experience of spiders and their webs.” It is painful to see this advanced as an argument.
Unflagging Success
DARWIN CONCEIVED of evolution in terms of small variations among organisms, variations which by a process of accretion allow one species to change continuously into another. This suggests a view in which living creatures are spread out smoothly over the great manifold of biological possibilities, like colors merging imperceptibly in a color chart.
Life, however, is absolutely nothing like this. Wherever one looks there is singularity, quirkiness, oddness, defiant individuality, and just plain weirdness. The male redback spider (Latrodectus hasselti), for example, is often consumed during copulation. Such is sexual cannibalism–the result, biologists have long assumed, of “predatory females overcoming the defenses of weaker males.” But it now appears that among Latrodectus basselti, the male is complicit in his own consumption. Having achieved intromission, this schnook performs a characteristic somersault, placing his abdomen directly over his partner’s mouth. Such is sexual suicide-awfulness taken to a higher power.(2)
It might seem that sexual suicide confers no advantage on the spider, the male passing from ecstasy to extinction in the course of one and the same act. But spiders willing to pay for love are apparently favored by female spiders (no surprise, there); and female spiders with whom they mate, entomologists claim, are less likely to mate again. The male spider perishes; his preposterous line persists.
This explanation resolves one question only at the cost of inviting another: why such bizarre behavior? In no other Latrodectus species does the male perform that obliging somersault, offering his partner the oblation of his life as well as his love. Are there general principles that specify sexual suicide among this species, but that forbid sexual suicide elsewhere? If so, what are they?
Once asked, such questions tend to multiply like party guests. If evolutionary theory cannot answer them, what, then, is its use? Why is the Pitcher plant carnivorous, but not the thorn bush, and why does the Pacific salmon require fresh water to spawn, but not the Chilean sea bass? Why has the British thrush learned to hammer snails upon rocks, but not the British blackbird, which often starves to death in the midst of plenty? Why did the firefly discover bioluminescence, but not the wasp or the warrior ant; why do the bees do their dance, but not the spider or the flies; and why are women, but not cats, born without the sleek tails that would make them even more alluring than they already are?
Why? Yes, why? The question, simple, clear, intellectually respectable, was put to the Nobel laureate George Wald. “Various organisms try various things,” he finally answered, his words functioning as a verbal shrug, “they keep what works and discard the rest.”
But suppose the manifold of life were to be given a good solid yank, so that the Chilean sea bass but not the Pacific salmon required fresh water to spawn, or that ants but not fireflies flickered enticingly at twilight, or that women but not cats were born with lush tails. What then? An inversion of life’s fundamental facts would, I suspect, present evolutionary biologists with few difficulties. Various organisms try various things. This idea is adapted to any contingency whatsoever, an interesting example of a Darwinian mechanism in the development of Darwinian thought itself.
A comparison with geology is instructive. No geological theory makes it possible to specify precisely a particular mountain’s shape; but the underlying process of upthrust and crumbling is well understood, and geologists can specify something like a mountain’s generic shape. This provides geological theory with a firm connection to reality. A mountain arranging itself in the shape of the letter “A” is not a physically possible object; it is excluded by geological theory.
The theory of evolution, by contrast, is incapable of ruling anything out of court. That job must be done by nature. But a theory that can confront any contingency with unflagging success cannot be falsified. Its control of the facts is an illusion.
Sheer Dumb Luck
CHANCE ALONE,” the Nobel Prize-winning chemist Jacques Monod once wrote, “is at the source of every innovation, of all creation in the biosphere. Pure chance, absolutely free but blind, is at the very root of the stupendous edifice of creation.”
The sentiment expressed by these words has come to vex evolutionary biologists. “This belief,” Richard Dawkins writes, “that Darwinian evolution is ‘random,’ is not merely false. It is the exact opposite of the truth.” But Monod is right and Dawkins wrong. Chance lies at the beating heart of evolutionary theory, just as it lies at the beating heart of thermodynamics.
It is the second law of thermodynamics that holds dominion over the temporal organization of the universe, and what the law has to say we find verified by ordinary experience at every turn. Things fall apart. Energy, like talent, tends to squander itself. Liquids go from hot to lukewarm. And so does love. Disorder and despair overwhelm the human enterprise, filling our rooms and our lives with clutter. Decay is unyielding. Things go from bad to worse. And overall, they go only from bad to worse.
These grim certainties the second law abbreviates in the solemn and awful declaration that the entropy of the universe is tending toward a maximum. The final state in which entropy is maximized is simply more likely than any other state. The disintegration of my face reflects nothing more compelling than the odds. Sheer dumb luck.
But if things fall apart, they also come together. Life appears to offer at least a temporary rebuke to the second law of thermodynamics. Although biologists are unanimous in arguing that evolution has no goal, fixed from the first, it remains true nonetheless that living creatures have organized themselves into ever more elaborate and flexible structures. If their complexity is increasing, the entropy that surrounds them is decreasing. Whatever the universe-as-a-whole may be doing–time fusing incomprehensibly with space, the great stars exploding indignantly–biologically things have gone from bad to better, the show organized, or so it would seem, as a counterexample to the prevailing winds of fate.
How so? The question has historically been the pivot on which the assumption of religious belief has turned. How so? “God said: ‘Let the waters swarm with swarms of living creatures, and let fowl fly above the earth in the open firmament of heaven.”‘ That is how so. And who on the basis of experience would be inclined to disagree? The structures of life are complex, and complex structures get made in this, the purely human world, only by a process of deliberate design. An act of intelligence is required to bring even a thimble into being; why should the artifacts of life be different?
Darwin’s theory of evolution rejects this counsel of experience and intuition. Instead, the theory forges, at least in spirit, a perverse connection with the second law itself, arguing that precisely the same force that explains one turn of the cosmic wheel explains another: sheer dumb luck.
If the universe is for reasons of sheer dumb luck committed ultimately to a state of cosmic listlessness, it is also by sheer dumb luck that life first emerged on earth, the chemicals in the pre-biotic seas or soup illuminated and then invigorated by a fateful flash of lightning. It is again by sheer dumb luck that the first self-reproducing systems were created. The dense and ropy chains of RNA–they were created by sheer dumb luck, and sheer dumb luck drove the primitive chemicals of life to form a living cell. It is sheer dumb luck that alters the genetic message so that, from infernal nonsense, meaning for a moment emerges; and sheer dumb luck again that endows life with its opportunities, the space of possibilities over which natural selection plays, sheer dumb luck creating the mammalian eye and the marsupial pouch, sheer dumb luck again endowing the elephant’s sensitive nose with nerves and the orchid’s translucent petal with blush.
Amazing. Sheer dumb luck.
Life, Complex Life
PHYSICISTS ARE persuaded that things are in the end simple; biologists that they are not. A good deal depends on where one looks. Wherever the biologist looks, there is complexity beyond complexity, the entanglement of things ramifying downward from the organism to the cell. In a superbly elaborated figure, the Australian biologist Michael Denton compares a single cell to an immense automated factory, one the size of a large city:
On the surface of the cell we would see millions of openings, like the portholes of a vast space ship, opening and closing to allow a continual stream of materials to flow in and out. If we were to enter one of these openings we would find ourselves in a world of supreme technology and bewildering complexity. We would see endless highly organized corridors and conduits branching in every direction away from the perimeter of the cell, some leading to the central memory bank in the nucleus and others to assembly plants and processing units. The nucleus itself would be a vast spherical chamber more than a kilometer in diameter, resembling a geodesic dome inside of which we would see, all neatly stacked together in ordered arrays, the miles of coiled chains of the DNA molecule . . . . We would notice that the simplest of the functional components of the cell, the protein molecules, were, astonishingly, complex pieces of molecular machinery . . . . Yet the life of the cell depends on the integrated activities of thousands, certainly tens, and probably hundreds of thousands of different protein molecules.
And whatever the complexity of the cell, it is insignificant in comparison with the mammalian nervous system; and beyond that, far impossibly ahead, there is the human mind, an instrument like no other in the biological world, conscious, flexible, penetrating, inscrutable, and profound.
It is here that the door of doubt begins to swing. Chance and complexity are countervailing forces; they work at cross-purposes. This circumstance the English theologian William Paley (1743-1805) made the gravamen of his well-known argument from design:
Nor would any man in his senses think the existence of the watch, with its various machinery, accounted for, by being told that it was one out of possible combinations of material forms; that whatever he had found in the place where he found the watch, must have contained some internal configuration or other, and that this configuration might be the structure now exhibited, viz., of the works of a watch, as well as a different structure. It is worth remarking, it is simply a fact, that this courtly and old-fashioned argument is entirely compelling. We never attribute the existence of a complex artifact to chance. And for obvious reasons: complex objects are useful islands, isolated amid an archipelago of useless possibilities. Of the thousands of ways in which a watch might be assembled from its constituents, only one is liable to work. It is unreasonable to attribute the existence of a watch to chance, if only because it is unlikely. An artifact is the overflow in matter of the mental motions of intention, deliberate design, planning, and coordination. The inferential spool runs backward, and it runs irresistibly from a complex object to the contrived, the artificial, circumstances that brought it into being.
Paley allowed the conclusion of his argument to drift from man-made to biological artifacts, a human eye or kidney falling under the same classification as a watch. “Every indication of contrivance,” he wrote, “every manifestation of design, exists in the works of nature; with the difference, on the side of nature, of being greater or more, and that in a degree which exceeds all computation.
In this drifting, Darwinists see dangerous signs of a non sequitur. There is a tight connection, they acknowledge, between what a watch is and how it is made; but the connection unravels at the human eye–or any other organ, disposition, body plan, or strategy–if only because another and a simpler explanation is available. Among living creatures, say Darwinists, the design persists even as the designer disappears.
“Paley’s argument,” Dawkins writes, “is made with passionate sincerity and is informed by the best biological scholarship of his day, but it is wrong, gloriously and utterly wrong.”
The enormous confidence this quotation expresses must be juxtaposed against the weight of intuition it displaces. It is true that intuition is often wrong-quantum theory is intuition’s graveyard. But quantum theory is remote from experience; our intuitions in biology lie closer to the bone. We are ourselves such stuff as genes are made on, and while this does not establish that our assessments of time and chance must be correct, it does suggest that they may be pertinent.
No comments:
Post a Comment