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More Articles on Evolution

The Limits of Darwinism

David Berlinski

The parts of an irreducibly complex system--a padlock, say--must work together if the system is to work at all. Such systems, Mike Behe has argued, are inaccessible to a Darwinian mechanism.

H. Allen Orr confidently demurs, the shade of H. J. Muller having persuaded him that irreducible complexity is itself an evolutionary property, something that simply pops up in the evolutionary record, like the vermiform appendix. Herewith, then, the Darwinian padlock. A key-like structure (a slug, perhaps) makes an adventitious appearance, followed by the equally adventitious appearance of a lock. The key then obligingly adapts itself to the lock, creating the familiar irreducibly complex padlock.

It is a defect of this scheme that the requisite steps involve two useless artifacts and a miracle.

I have, of course, rigged the example for rhetorical effect, but Orr's argument is in any case an exercise is misapplied force, like a screw hammered into wood. Whatever the definition of irreducible complexity, some systems must remain inaccessible to a Darwinian mechanism if the underlying theory is to have empirical content. Witness the lock and key. A universal evolutionary mechanism is no more plausible than a universal differential equation. The only question of interest is whether some biological structures are included among the systems inaccessible to every Darwinian mechanism. The conceptual question aside, the incontrovertible fact remains that in biochemistry the requisite Darwinian intermediates are missing from the literature and nowhere to be seen in life. This is the gravamen of Behe's argument. And it is to Behe's credit that he has made it.

Having for many years declined to discuss the obvious, evolutionary biologists now argue that the facts to which Behe is drawing attention represent merely an irregularity in the otherwise smooth manifold of Darwinian successes.

Their response would, of course, be more persuasive if those successes were more conspicuous. The achievements of contemporary biology are very considerable. In this, Orr is entirely correct. But it has been the molecular biologists and biochemists who have discovered an entirely new, entirely limpid, entirely lovely and astonishing new world, this even as evolutionary biologists have continued to trot restlessly across the same dark plain, baying at shadows in the endless night.

I very much enjoyed the appetizers of Berwick's discussion, but found myself disappointed that the main course appears to be missing.

I shall supply it myself. On n'est jamais aussi bien servi que par soi mÍme. Richard Dawkins has set himself the formidable task of providing an explanation of biological complexity. Yet Climbing Mount Improbable contains neither a serious study of any organ nor a sober analytical discussion of any theory. The argument in favor of random variation and natural selection is sustained chiefly by the conviction that it has been defended elsewhere, a point of view evident also in Dennett's Darwin's Dangerous Idea.

The problems confronting evolutionary theory are by no means trivial. We are largely unable to characterize what evolution has accomplished and so logically in no position to determine whether evolution has accomplished it. No very precise definition of an organism is at hand: indeed, no definition at all. Many properties of living creatures remain resistant to specification, let alone explanation, a fact that becomes embarrassingly evident whenever attempts are made to simulate aspects of animal life. Computer models exist that mimic bird flocking, but no one has the faintest idea how to represent algorithmically the fact that the behavior of higher organisms is in some measure autonomous. Our understanding of various biological systems is profoundly incomplete. Vision is a case in point. Inasmuch as the visual system issues in a visual experience, a satisfactory theory of vision must resolve the problem of consciousness. If we knew the laws governing evolution, we should be able mathematically to describe a Darwinian mechanism and by specifying its initial state and boundary conditions see certain portions of the evolutionary record repeat themselves. This would offer biologists the opportunity to do what is commonly done in astrophysics, and that is to compare such simulations with the real world. We can do no such thing. The discipline hilariously described as artificial life, a worthy successor, no doubt, to artificial intelligence, has succeeded only in showing that where simulations proceed according to Darwinian algorithms, nothing life-like can be expected; and where something life-like can be expected, simulations have not proceeded according to Darwinian algorithms.

From a mathematical point of view, Darwinian theories appear far too weak to have brought about the remarkable structures evident in living creatures. Finite state automata and finite state Markov processes are systems of generous and demonstrable inadequacy in psychology, a circumstance that evolutionary biologists tend to ignore, perhaps because it embodies facts with which they are not acquainted.

Curiously enough, biologists are sometimes prepared to endorse these harsh conclusions, as long as the gross deficiencies in Darwinian theory may respectfully be represented as work in progress. In a recent issue of Science,1 a quartet of theoretical biologists survey what is currently absent from evolutionary theory. Interesting mathematical models. An explanation for the evolutionary increase in information and complexity. Any plausible account of biological organization. An explanation of the major macro-evolutionary changes: the emergence of life, the appearance of eukaryotic cells, the human capacity for language. Theories of variation and theories of development.

In the largest sense, we do not know whether life is determined by the laws of physics and chemistry, or whether it is consistent with but independent of those laws, or whether it is the expression of a profound but inscrutable design. Dogmatic assertions in the face of ignorance express nothing more than a lack of interest in rational inquiry. It is for this reason that otherwise sympathetic observers have come to the conclusion that Richard Dawkins is motivated as much by a theological agenda as scientific curiosity.

Now that is the main course I would have wished to see.

1 Torbjorn Faserstrom et al., "Biologists Put on Mathematical Glasses," in Science 274 (December 20, 1996): 2039-40.

Originally published in the February/ March 1997 issue of Boston Review

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