Full House (15 page)

Part Four

THE MODAL BACTER:
WHY PROGRESS DOES NOT
RULE THE HISTORY
OF LIFE

12

The Bare Bones of Natural Selection

I quote verbatim from a discussion held in 1959:

HUXLEY: I once tried to define evolution in an overall way somewhat along these lines: a one way process, irreversible in time, producing apparent novelties and greater variety and leading to higher degrees of organization.

DARWIN: What is "higher"?

HUXLEY: More differentiated, more complex, but at the same time more integrated.

DARWIN: But parasites are also produced.

HUXLEY: I mean a higher degree of organization in general, as shown by the upper level attained.

Charles Darwin died in 1882, Thomas Henry Huxley in 1895—so, unless I am reporting a seance, something strange is going on here. The date of 1959 might give a hint for aficionados, for Charles Darwin published the Origin of Species in 1859, and the interval of exactly one hundred years smells of a centennial celebration. Huxley, in fact, is Thomas Henry’s grandson Julian, an eminent biologist and statesman in his own right, while Darwin is Charles’s grandson, also Charles, and also a scientist and social thinker. The two grandsons held their dialogue at the largest centennial celebration for Charles Darwin’s Origin of Species, held at the University of Chicago in 1959 and published in 1960 as an influential three-volume work edited by Sol Tax.

Not only did the Darwin and Huxley clans maintain a genealogical tradition for evolutionary studies, but also, and more curiously as we shall see, the errors and insights of modern Chicago’s Darwin and Huxley closely parallel the attitudes of their blood ancestors. Julian makes the same errors as Thomas Henry; Charles offers some of the same correctives as the elder Charles. Both are confused on the notion of progress. Darwin asks a good question about parasites—and so did his grandfather. Julian Huxley gives a muddled answer that contains the germ of resolution within the standard, central confusion.

The problem that spawns this confusion within the Darwinian tradition may be simply stated as a paradox. The basic theory of natural selection offers no statement about general progress, and supplies no mechanism whereby overall advance might be expected. Yet both Western culture and the undeniable facts of a fossil record that started with bacteria alone, and has now produced exalted us, cry out in unison for a rationale that will place progress into the center of evolutionary theory.

Charles Darwin reveled in the radical nature of his biological philosophy. His early and private notebooks practically shout for joy at the outrageous character of his valid conjectures. He writes to himself, for example, that our feelings of reverence for God arise from some feature of our neurological organization. Only our arrogance, he continues, makes us so reluctant to ascribe our thoughts to a material substrate:

Love of the deity [an] effect of organization, oh you materialist! ... Why is thought being a secretion of brain, more wonderful than gravity a property of matter? It is our arrogance, our admiration of ourselves.

Darwin toned down his exultation as he grew older and presented his work for public appraisal, but he never abandoned his radical perspective—and we have therefore, as discussed in Part One, never been able or willing to complete his revolution in Freud’s sense by owning the true implications of Darwinism for the dethronement of human arrogance. None of Darwin’s outré ideas could have been more unacceptable than his denial of progress as a predictable outcome of the mechanisms of evolutionary change. Most other nineteenth-century evolutionists, including Lamarck, presented much more congenial theories that did include predictable progress as a central ingredient. In fact, evolution entered our language as the favored word for what Darwin had called "descent with modification" because most Victorian thinkers equated such biological change with progress—and the word evolution, propelled into biology by the advocacy of Herbert Spencer, meant progress (literally "unfolding") in the English vernacular. Darwin initially resisted the word because his theory embodied no notion of general advance as a predictable consequence of any mechanism of change. Evolution never appears in the first edition of the Origin of Species, and Darwin first used the word in The Descent of Man in 1871. He never liked evolution, and only acquiesced because Spencer’s term had gained general currency.

Darwin was not shy in advertising his nonprogressivism. He jotted a note in the margins of a major book that did advocate progress in the history of life: "Never say higher or lower." He wrote the following line in a letter (December 4, 1872) to the paleontologist Alpheus Hyatt, who had proposed an evolutionary theory based on intrinsic progress (I now inhabit Hyatt’s old office, so the connection has a special meaning for me): "After long reflection, I cannot avoid the conviction that no innate tendency to progressive development exists."

Darwin’s denial of progress arises for a special and technical reason within his theory, and not merely from a general philosophical preference. In a famous anecdote, T. H. Huxley, upon first learning the content of Darwin’s theory of natural selection, proclaimed himself "extremely stupid" not to have figured out this principle by himself. Unlike other celebrated (and truly arcane) ideas in the history of science, natural selection is a remarkably simple notion—basically three undeniable facts followed by an obvious, almost syllogistic conclusion. (I speak of simplicity only for the "bare bones" of natural selection as a mechanism; the inferences and implications that flow from the operation of selection can be quite subtle and complex.)

Darwin devotes the beginning chapters of the Origin of Species to validating the three facts:

All organisms tend to produce more offspring than can possibly survive (Darwin’s generation gave this principle the lovely name of "super-fecundity").

Offspring vary among themselves, and are not carbon copies of an immutable type.

At least some of this variation is passed down by inheritance to future generations. (Darwin did not know the mechanism of heredity, for Mendel’s principles did not gain acceptance until early in our century. However, this third fact requires no knowledge of how heredity works, but only an acknowledgment that heredity exists. And mere existence is undeniable folk wisdom. We know that black folks have black kids; white folks, white kids; tall parents tend to have tall children; and so on.)

The principle of natural selection then emerges as a necessary inference from these facts:

If many offspring must die (for not all can be accommodated in nature’s limited ecology), and individuals in all species vary among themselves, then on average (as a statistical statement, and not in every case), survivors will tend to be those individuals with variations that are fortuitously best suited to changing local environments. Since heredity exists, the offspring of survivors will tend to resemble their successful parents. The accumulation of these favorable variants through time will produce evolutionary change.

If this presentation seems overly abstract, consider a potential example (something of a simplistic caricature, to be sure, but not bad as a representation of the central features of Darwin’s argument): an earlier Siberia is nicely temperate, and a population of minimally hairy elephants dwells there in excellent adaptation. As the earth enters a glacial age, and ice begins to build up to the north, climates become colder and possession of more than the usual amount of hair becomes a decided advantage. On average, the hairier elephants will be more successful and therefore leave more surviving offspring. (On average, that is, and not every time—the hairiest elephant in the population can still slip into a crevasse and die.) Since hairiness is inherited, the next generation will contain more elephants with increased hair (for the hairiest of the last generation enjoyed greater success in reproduction). Continue this process for a large number of generations, and eventually Siberia will house a population of woolly mammoths—the evolutionary descendants of the original elephants.

Fine, in outline. But note what this scenario leaves out (that almost all popular views of evolution include as a defining feature). Natural selection talks only about "adaptation to changing local environments"; the scenario includes no statement whatever about progress—nor could any such claim be advanced from the principle of natural selection. The woolly mammoth is not a cosmically better or generally superior elephant. Its only "improvement" is entirely local; the woolly mammoth is better in cold climates (but its minimally hairy ancestor remains superior in warmer climates). Natural selection can only produce adaptation to immediately surrounding (and changing) environments.

No feature of such local adaptation should yield any expectation of general progress (however such a vague term be defined). Local adaptation may as well lead to anatomical simplification as to greater complexity. As an adult, the famous parasite Sacculina, a barnacle by ancestry, looks like a formless bag of reproductive tissue attached to the underbelly of its crab host (with "roots" of equally formless tissue anchored within the body of the crab itself)—a devilish device to be sure (at least by our aesthetic standards), but surely less anatomically complex than the barnacle on the bottom of your boat, waving its legs through the water in search of food.

If a sequence of local environments could elicit progressive advance through time, then some expectation of progress might be drawn from natural selection. But no such argument seems possible. The sequence of local environments in any one place should be effectively random through geological time—the seas come in and the seas go out, the weather gets colder, then hotter, etc. If organisms are tracking local environments by natural selection, then their evolutionary history should be effectively random as well.

These arguments led Darwin to his denial of progress as a consequence of the "bare bones mechanics" of natural selection—for this process yields only local adaptation, often exquisite to be sure, but not universally advancing. The mammoth is every bit as good as an elephant—and vice versa. Do you prefer a marlin for its excellent spike; a flounder for its superb camouflage; an anglerfish for its peculiar "lure" evolved at the end of its own dorsal fin ray; a seahorse for its wondrous shape, so well adapted for bobbing around its habitat? Could any of these fishes be judged "better" or "more progressive" than any other? The question makes no sense. Natural selection can forge only local adaptation—wondrously intricate in some cases, but always local and not a step in a series of general progress or complexification.

Darwin reveled in this unusual feature of his theory—this mechanism for immediate fit alone, with no rationale for increments of general progress or complexification. So far, so good; so logical, so clear. I should end my discussion of Darwin right here, extolling him as a consistent intellectual radical whose vision of a history of life devoid of predictable progress proved too much for his Western compatriots to accept.

Simple, and heroic for Darwin, but quite untrue—for real history (and biography) tends to be much messier. Actual lives, especially for brilliantly complex men like Darwin, abound in pieces that don’t quite mesh, or that truly contradict. Darwin was intellectually radical; but he was also politically liberal, a defender of mild social reform and a passionate opponent of slavery; and decidedly conservative in lifestyle—a wealthy country squire himself, reared in the same background, and with no desire to change the amenities of his comfortable existence.

Moreover, Darwin enjoyed this comfort in a society that, more than any other in human history, had enshrined progress as the fundamental doctrine of its meaning and being—Victorian Britain at the height of industrial and colonial expansion. How could a patrician Englishman, at the very apex of his nation’s thundering success, abjure the principle that embodied this triumph? And yet, natural selection could produce only local adaptation, not general progress. How could these contradictory needs— the intellectual and the social—be reconciled?

These conflicting loyalties achieve their sharpest expression in a remarkable sentence that Darwin placed in a most conspicuous position— on the last page of the Origin of Species, just before the famous concluding paragraph about "grandeur in this view of life."

As natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress towards perfection.

Note the starkness of the claim. Darwin says "all" endowments—including all attributes of mind, as well as all features of bodies. How, after proclaiming with such panache (as quoted earlier) that natural selection undermines the old dogma of progress, could Darwin write such a sentence?

Darwin’s apparent contradictions on the subject of progress have sparked a large literature among historians of science. Entire books have been dedicated to the subject (see Richards, 1992). Most efforts have been devoted to constructing forced and arcane rationales that would render all of Darwin’s statements consistent. But I would take another view, based on Emerson’s famous dictum that "a foolish consistency is the hobgoblin of little minds," or upon Walt Whitman’s wonderful lines in his "Song of Myself":

Do I contradict myself?
Very well then, I contradict myself,
(I am large, I contain multitudes).

I believe that Darwin’s views contain an unresolved inconsistency. Darwin, the intellectual radical, knew what his own theory entailed and implied; but Darwin, the social conservative, could not undermine the defining principle of a culture (at a key moment of history) to which he felt such loyalty, and in which he dwelt with such comfort.

Darwin did, of course, supply an argument to bridge the two starkly contradictory claims—that the mechanics of natural selection produces only local adaptation, not general progress; and that all mental and corporeal endowments advance toward perfection in the history of life. He could not, after all, leave such a gaping logical hole in his oeuvre. Darwin tried to plug the hole by adding a set of statements about ecology to the "bare bones mechanics" that could not, by itself, validate progress.