The story of terrestrial vertebrates is just as egregiously biased. First of all, once vertebrates colonize the land, oceans disappear from life's history, with one "exception" (documented in Figure 1) that actually illustrates the rule: If a "highly evolved" land creature returns to the sea, it may be shown as a representative of diversity within a stage of progress. Thus, Mesozoic marine reptiles may be depicted as contemporaries of ruling dinosaurs on land, but fishes living at the same time are invisible because their stage has been superseded in evolution's upward march. Tertiary whales are in because mammals then rule the land, but both marine reptiles and fishes of the same period are out as bypassed forms.
Second, the sequence of land animals only displays our anthropocentric view of shifting mastery through time, not a fair record of changing diversity. Fishes are banished once amphibians and reptiles colonize the land—but why punish fishes for what a few odd relatives did in disparate and unknown environments, especially when oceans, continuously dominated by fishes among vertebrates, cover some 70 percent of the earth's surface? The origin of mammals extirpates all amphibians and reptiles from view, even though they continue to flourish and to influence mammalian life in ways ranging from Mosaic plagues to the temptation of Eve. The last few paintings always depict humans, even though we are but one species in a small group of mammals (the order Primates contains about two hundred species among four thousand or so for all mammals), while the greatest successes of mammalian evolution—bats, rats, and antelopes—remain invisible.
Let me not carp unfairly. If these pageantries only claimed to be illustrating the ancestry of our tiny human twig on life's tree, then I would not complain, for I cannot quarrel unduly with such a parochial decision, stated up front. But these iconographic sequences always purport to be illustrating _the_ history of life, not a tale of a twig. Consider the titles of the three series partly depicted in Figure 1: "The earth before the flood," "The parade of life through the ages," and "Prehistoric animals." An analogy might help in illustrating the oddity of such a pageant: Suppose that we wanted to stage a parade illustrating the growth of America's coterminous forty-eight states through time. Would we let the float for New England ride only for the first mile, and then withdraw it permanently from view? Would we then add the Northwest Territories, the Louisiana Purchase, and the western lands in sequence, permitting only one float at a time by—dismantling the preceding float after each new introduction? Would we be adequately showing the apotheosis of American expansion if the parade ended with a single float celebrating that little sliver of the southwest known as the Gadsden Purchase?
Similarly, much as we may love ourselves, _Homo sapiens_ is not representative, or symbolic, of life as a whole. We are not surrogates for arthropods (more than 80 percent of animal species), or exemplars of anything either particular or typical. We are the possessors of one extraordinary evolutionary invention called consciousness—the factor that permits us, rather than any other species, to ruminate about such matters (or, rather, cows ruminate and we cogitate). But how can this invention be viewed as the distillation of life's primary thrust or direction when 80 percent of multicellularity (the phylum Arthropoda) enjoys such evolutionary success and displays no trend to neurological complexity through time—and when our own neural elaboration may just as well end up destroying us as sparking a move to any other state that we would choose to designate as "higher"?
Why, then, do we continually portray this pitifully limited picture of one little stream in vertebrate life as a model for the whole multicellular pageant? Yet how many of us have ever looked at such a standard iconographic sequence and raised any question about its basic veracity? The usual iconography seems so right, so factual. I shall argue in this book that our unquestioning approbation of such a scheme provides our culture's most prominent example of a more extensive fallacy in reasoning about trends—a focus on particulars or abstractions (often biased examples like the lineage of _Homo sapiens_), egregiously selected from a totality because we perceive these limited and uncharacteristic examples as moving somewhere—when we should be studying variation _in the entire system_ (the "full house" of my title) and its changing pattern of spread through time. I will emphasize the set of trends that inspires our greatest interest—supposed improvements through time. And I shall illustrate an unconventional mode of interpretation that seems obvious once stated, but rarely enters our mental framework—trends properly viewed as results of expanding or contracting variation, rather than concrete entities moving in a definite direction. This book, in other words, treats the _"spread of excellence,"_ or trends to improvement best interpreted as expanding or contracting variation.
2
Darwin Amidst the Spin Doctors
Biting the Fourth Freudian Bullet
I have often had occasion to quote Freud's incisive, almost rueful, observation that all major revolutions in the history of science have as their common theme, amidst such diversity, the successive dethronement of human arrogance from one pillar after another of our previous cosmic assurance. Freud mentions three such incidents: We once thought that we lived on the central body of a limited universe until Copernicus, Galileo, and Newton identified the earth as a tiny satellite to a marginal star. We then comforted ourselves by imagining that God had nevertheless chosen this peripheral location for creating a unique organism in His image—until Darwin came along and "relegated us to descent from an animal world." We then sought solace in our rational minds until, as Freud notes in one of the least modest statements of intellectual history, psychology discovered the unconscious.
Freud's statement is acute, but he left out several important revolutions in the pedestal-smashing mode (I offer no criticism of Freud's insight here, for he tried only to illustrate the process, not to provide an exhaustive list). In particular, he omitted the major contribution made to this sequence by my own field of geology and paleontology—the temporal counterpart to Copernicus's spatial discoveries. The biblical story, read literally, was so comforting: an earth only a few thousand years old, and occupied for all but the first five days by humans as dominant living creatures. The history of the earth becomes coextensive with the story of human life. Why not, then, interpret the physical universe as existing for and because of us?
But paleontologists then discovered "deep time," in John McPhee's felicitous phrase. The earth is billions of years old, receding as far into time as the visible universe extends into space. Time itself poses no Freudian threat, for if human history had occupied all these billions, then we might have increased our arrogance by longer hegemony over the planet. The Freudian dethronement occurred when paleontologists revealed that human existence only fills the last micromoment of planetary time—an inch or two of the cosmic mile, a minute or two in the cosmic year. This phenomenal restriction of human time posed an obvious threat, especially in conjunction with Freud's second, or Darwinian, revolution. For such a limitation has a "plain meaning"—and plain meanings are usually correct (even though many of our most fascinating intellectual revolutions celebrate the defeat of apparently obvious interpretations); If we are but a tiny twig on the floridly arborescent bush of life, and if our twig branched off just a geological moment ago, then perhaps we are not a predictable result of an inherently progressive process (the vaunted trend to progress in life's history); perhaps we are, whatever our glories and accomplishments, a momentary cosmic accident that would never arise again if the tree of life could be replanted from seed and regrown under similar conditions.
In fact, I would argue that all these "plain meanings" are true, and that we should revel in our newfound status and attendant need to construct meanings by and for ourselves—but this is another story for another time. I called this other story _Wonderful Life_ (Gould, 1989). The theme for the present book, something of a philosophical "companion volume," is _Full House_—For now, I only point out that this plain meaning is profoundly antithetical to some of the deepest social beliefs and psychological com
forts of Western life—and that popular culture has therefore been unwilling to bite this fourth Freudian bullet.
Only two options seem logically available in our attempted denial. We might, first of all, continue to espouse biblical literalism and insist that the earth is but a few thousand years old, with humans created by God just a few days after the inception of planetary time. But such mythology is not an option for thinking people, who must respect the basic factuality of both time's immensity and evolution's veracity. We have therefore fallen back upon a second mode of special pleading—Darwin among the spin doctors. How can we tell the story of evolution with a slant that can validate traditional human arrogance?
If we wish both to admit the restriction of human time to the last micromoment of planetary time, and to continue our traditional support for our own cosmic importance, then we have to put a spin on the tale of evolution. I believe that such a spin would seem ridiculous _prima facie_ to the metaphorical creature so often invoked in literary works to symbolize utter objectivity—the dispassionate and intelligent visitor from Mars who arrives to observe our planet for the first time, and comes freighted with no _a priori_ expectations about earthly life. Yet we have been caught in this particular spin so long and so deeply that we do not grasp the patent absurdity of our traditional argument.
This positive spin rests upon the fallacy that evolution embodies a fundamental trend or thrust leading to a primary and defining result, one feature that stands out above all else as an epitome of life's history. That crucial feature, of course, is progress—operationally defined in many different ways[1] as a tendency for life to increase in anatomical complexity, or neurological elaboration, or size and flexibility of behavioral repertoire, or any criterion obviously concocted (if we would only be honest and introspective enough about our motives) to place _Homo sapiens_ atop a supposed heap.
[1. One basically sophistic argument against progress holds that the word itself is too vague or subjective, and that the concept should be dropped for lack of rigor in description. This argument is a cop-out, and I will certainly not invoke such a lame defense in this book. Progress is too vague to stand by itself, but a variety of operational surrogates have been proposed—ranging from something as precise and measurable as brain size to more general, but still definable, notions as anatomical complexity (usually construed as number of parts and their degree of differentiation, assessed in various ways). I shall argue that progress as the primary thrust of lire's history cannot be defended even for these operational surrogates.]
We might canvass a range of historians, psychologists, theologians, and sociologists for their own distinctive views on why we feel such a need to validate our existence as a predictable cosmic preference. I can speak only from my own perspective as a paleontologist in the light of the fourth Freudian revolution; We are driven to view evolution's thrust as predictable and progressive in order to place a positive spin upon geology's most frightening fact—the restriction of human existence to the last sliver of earthly time. With such a spin, our limited time no longer threatens our universal importance. We may have occupied only the most recent moment as _Homo sapiens_, but if several billion preceding years displayed an overarching trend that sensibly culminated in our mental evolution, then our eventual origin has been implicit from the beginning of time. In one important sense, we have been around from the start. _In principio erat verbum_.
We may easily designate belief in progress as a potential bias, but some biases are true: my utterly subjective rooting preferences led me to love the Yankees during the 1950s, but they were also, objectively, the best team in baseball. Why should we suspect that progress, as the defining thrust of life's history, is not true? After all, and quite apart from our wishes, doesn't life manifestly become more complex? How can such a trend be denied in the light of paleontology's most salient fact: In the beginning, 3.5 billion years ago, alt living organisms were single cells of the simplest sort, bacteria and their cousins; now we have dung beetles, seahorses, petunias, and people. You would have to be a particularly refractory curmudgeon, one of those annoying characters who loves verbal trickery and empty argument for its own sake, to deny the obvious statement that progress stands out as the major pattern of life's history.
This book tries to show that progress is, nonetheless, a delusion based on social prejudice and psychological hope engendered by our unwillingness to accept the plain (and true) meaning of the fourth Freudian revolution. I shall not make my case by denying the basic fact just presented: Long ago, only bacteria populated the earth; now, a much broader diversity includes _Homo sapiens_. I shall argue instead that we have been thinking about this basic fact in a prejudiced and unfruitful way—and that a radically different approach to trends, one that requires a revision of even more basic mental habits dating at least to Plato, offers a more profitable framework. This new vantage point will also help us to understand a wide range of puzzling issues from the disappearance of 0.400 hitting in baseball to the absence of modern Mozarts and Beethovens.
Can We Finally Complete Darwin's Revolution?
The bias of progress expresses itself in various ways, from naive versions of pop culture to sophisticated accounts in the most technical publications. I do not, of course, claim that all, or even many, people accept the maximally simplistic account of a single ladder, with humans on top—although this imagery remains widespread, even in professional journals. Most writers who have studied some evolutionary biology understand that evolution is a copiously branching bush with innumerable present outcomes, not a highway or a ladder with one summit. They therefore recognize that progress must be construed as a broad, overall, average tendency (with many stable lineages "failing" to get the "message" and retaining fairly simple form through the ages).
Nonetheless, however presented, and however much the sillier versions may be satirized and ridiculed, claims and metaphors about evolution as progress continue to dominate all our literatures—testimony to the strength of this primary bias. I present a few items, almost randomly selected from my burgeoning files:
* From _Sports Illustrated_, August 6, 1990, Denver Broncos veteran Karl Mecklenburg, on being shitted from defensive end to inside linebacker to a new position as outside linebacker: "I'm moving right up the evolutionary ladder."
* From a correspondent, writing from Maine on January 18, 1987, and puzzled because he cannot spot the fallacy in a creationist tract: The pamphlet "shows that well dated finds of many species of man show no advancement within a species over the thousands of years the species existed. Also many species appear to have existed concurrently. Both these finds contradict the precepts of evolution which insists each species advances towards the next higher."
* From another correspondent, in New Jersey (December 22, 1992), a professional scientist this time, expressing his understanding that life as a totality, not just selected lineages at pinnacles of their groups, should progress through time: "I assume that as evolution proceeds, a greater and greater degree of specialization occurs with regard to structure and physiological activity. After a billion years or more of biological evolution I would think that the extant species are relatively highly specialized."
* From a correspondent in England on June 16, 1992, really putting it on the line: "Life has a sort of 'built-in' drive towards complexity, matched by no drive to decomplexity...Human consciousness was inevitable once things got started on Complexity Road in the first place."
* From a leading high school biology textbook, published in 1966, and providing a classic example of a false inference (the first sentence) drawn from a genuine fact (the second sentence): "Most descriptions of the pattern of evolution depend upon the assumption that organisms tend to become more and more complicated as they evolve. If this assumption is correct, there would have been a time in the past when the earth was in habited only by simple organisms."
* From America's leading professional journal, _Science_, in July 1993: An article titled "Trac
ing the Immune System's Evolutionary History" rests upon the peculiar premise, intelligible only if "everybody knows" about life's progress through time, that we should be surprised to discover sophisticated immune devices in "the lower organisms" (their phrase, not mine). The article claims to be reporting a remarkable insight: "the immune system in simpler organisms isn't just a less sophisticated version of our own." (Why should anyone have ever held such a view of "others" as basically "less than us," especially when the "simpler organisms" under discussion are arthropods with 500 million years of evolutionary separation from vertebrates, and when all scientists recognize the remarkable diversity and complexity of chemical defense systems maintained by many insects?) The article also expresses surprise that "creatures as far down the evolutionary ladder as sponges can recognize tissue from other species." If our leading professional journal still uses such imagery about evolutionary ladders, why should we laugh at Mr. Mecklenburg for his identical metaphor?
The allure of this conventional imagery is so great that I have fallen into the trap myself—by presenting my examples as an ascending ladder from the central pop icon of a sports hero, through letters of increasing sophistication, to textbooks, to an article in Science. Yet the last shall be first, and my linear sequence bends into a circle of error, as both my initial and final examples misuse the identical phrase about an "evolutionary ladder." At least the linebacker was trying to be funny!
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