Gould, Tires to Sandals

motor of construction, must still be the processes of normal times building creatures that will one day pass for review before the sieve of mass extinction. And the controlling process of normal times is wedging by competition.

I could rebut this argument in several ways. I might argue, for example, that sorting by differential death in mass extinction mimics, on a grander scale, the ordinary mode of operation for natural selection in normal times. Natural selection is a sieve, not a sculptor. Many are called; few are chosen. Natural selection is powered by differential birth and death; the few survivors accumulate and intensify their favorable features bit by bit on the relentless sieve of each generation. What is mass extinction but a grander sieve, sorting out species rather than organisms. If the sorting of organisms in normal times yields change that we label as positive, why not grant the same status to differential death in episodic catastrophes? Mass extinction need not be viewed as a negative force opposed to progress in normal times.

But I would choose an opposite tack to provide the other half-loaf to the wheel of fortune. Rather than promoting the wheel of mass extinction by its formal similarity to processes at smaller scale, I would proceed in the reverse direction. I would argue, in short, that the fundamental principle of quirky and unpredictable success by fortuitous side consequences pervades all scales. This vital domain of the wheel does not "click in" only at global catastrophe, leaving most of time to the wedge of ordered progress. The tires-to-sandals principle works at all scales and times, interacting with the wedge to permit odd and unpredictable initiatives at any moment--to make nature as inventive as the cleverest person who ever pondered the potential of a junkyard in Nairobi.

I will go further and make a statement that may seem paradoxical. The wedge of competition has been, ever since Darwin, the canonical argument for progress in normal times. I will claim that the wheel of quirky and unpredictable functional shift (the tires-to-sandals principle) is the major source of what we call progress at all scales. Advance in complexity, improvement in design, may be mediated by the wedge up to a certain and limited point, but long-term success requires feinting and lateral motion, with each zig permitting another increment of advance, and progress crucially dependent upon the availability of new channels. Evolution is an obstacle course not a freeway; the correct analogue for long-term success is a distant punt receiver evading legions of would-be tacklers in an oddly zigzagged path toward a goal, not a horse thundering down the flat.

Let us take the broadest possible look at just three prerequisites for continuity in the sequence that, in our parochialism, we view as the crucial and representative case of evolutionary advance--the origin of human consciousness. At each true turning point, each leap in the capacity for substantial advance, we meet the wheel spinning its way toward a new use for old features (sandals from tires); the wedge can only promote, for a limited time and extent, what the wheel makes possible.

1. Origin of the genetic flexibility for major advance in complexity. For evolutionists, perhaps the most intriguing and unexpected discovery of molecular genetics emerged during the 1960s when study after study proved that in multicellular organisms, only a small percentage of the total genetic material consists of functional genes in single copies. Most of the genetic material may be "junk" with respect to information needed to build and maintain a working body. Moreover, many genes exist in multiple copies for obscure reasons unrelated to the necessary functions of bodies.

Nonetheless, it soon became clear to evolutionists that redundancy of multiple copies might be the crucial prerequisite for evolution of complexity. Suppose that the original unicellular ancestor of all complex creatures had only one copy of each gene and that each gene coded for a vital function. (This claim is not mere conjecture, but represents the actual state of the simplest creatures alive today and the best models for ultimate multicellular ancestors.) These creatures work very well; they may be honed to an optimum by natural selection, shorn of all unneeded fat and flab. But now, a conundrum for evolution: These creatures may excite our admiration for efficiency, but how can they change in the crucial sense of adding new capacities in complexity? Each gene codes for something vital; it can only alter by improvement in its own channel. This kind of genetic system offers no flexibility; no play, no capacity for adding something truly new.

This conundrum led evolutionists to grasp the fundamental role of multiple copies in permitting the evolution of complexity. If genes exist in several copies, but only one supplies the body's functional need, then the other copies are free to experiment, vary, and add capacity through occasional good fortune.

Well and good so far, but we now face a logical puzzle: Unless we thoroughly misunderstand the fundamental nature of causality, multiple copies cannot arise "for" their potential use in permitting complexity millions of years in the future. Multiple copies are the key to complexity, but they must have evolved for other reasons--the tires-to-sandals principle of quirky functional shift.

This case is particularly interesting because the initial reason for duplication (harvesting of rubber for tires) may not, itself, have much to do with natural selection as traditionally conceived in terms of organisms struggling for reproductive success. Duplication may arise by selection at the lower level of genes, a process invisible in the larger world of the wedge. Genes also play the game of natural selection in their own realm, and those that develop the capacity to duplicate and move (transposons, or jumping genes) secure advantages at this lower level, just as organisms win in Darwin's world by leaving more surviving offspring. In fact, gene duplication may be abetted by producing no effect upon bodies, for invisibility at Darwin's level of the wedge provides hiding space and assures that no negative pressures of natural selection shall impede the accumulation of "unneeded" extra copies. Yet these "redundant" duplicate genes may house the latent source of later complexity.

2. The evolution of complex cells. Many biologists would place nature's fundamental distinction not between plants and animals, or even between unicellular and multicellular organisms, but at a division within unicellular creatures. The structurally simple prokaryotes, bacteria and cyanophytes, have no organelles within their cells--no nucleus or chromosomes, no mitochondria. The complex eukaryotes have evolved the array of internal structures that grace (or disfigure according to your view or status) nearly every high school biology final with its inevitable question: label all the parts of the cell and state their functions.

This increment of complexity from prokaryote to eukaryote is deemed fundamental, in part because we view eukaryote organization as an absolute prerequisite to the later evolution of multicellular organisms. (To cite just one standard argument: Darwinian evolution of complexity requires copious variation to fuel natural selection; most variation arises from the mixture, via sexual reproduction, of two differing genetic systems in each offspring; sexual reproduction requires a mechanism for exact division of genetic material so that 50 percent of each parent reconstitutes the needed 100 percent in offspring; meiosis by reduction division of paired chromosomes is the biological in-

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