The Flamingo’s Smile (35 page)

Wallace then claims that solar stability cannot (as we believe today) arise as a product of a star’s own fuel supply (he knew little of radioactivity and nuclear fusion). Stars can burn steadily only if they are constantly supplied with new matter flowing from elsewhere. This matter moves, by gravitation, from outer regions of the universe (particularly from the ring of the Milky Way) toward the center, where our sun resides. The inner ring cannot harbor stable suns, since too much extraneous matter bombards it. The center of the solar cluster won’t do, because it receives too little nurturing material. Only at the outer edge of the solar cluster, where (and surely by design) our sun resides, can a star obtain the proper balance of material to burn steadily for enough time to foster the evolution of intelligence.

Every detail of cosmic design conspires to permit life on a planet circling such a fortunately situated sun. We need the Milky Way to supply external fuel. We need the inner ring as a filter, allowing just the right amount of fuel to pass through. We need a central cluster where stars move slowly and do not interfere with each other. Could all this have happened without some directing intelligence? Eighty years after Wallace’s book, our universe could not be more radically different, yet human hope continues to impose the same invalid argument upon it.

A final, important difference separates Wallace from Dyson and most modern supporters of the anthropic principle. Our contemporary advocates develop their arguments and then present their conclusion—that mind designed the universe, in part so that intelligent life might evolve within it—as a necessary and logical inference. Wallace was far too good a
historical
scientist to indulge in such fatuous certainty; he understood only too well that ordered and complex outcomes can arise from accumulated improbabilities. He therefore recognized and presented forthrightly the alternative interpretation:

This fine scientist, wearied by age and by so many lonely battles for idiosyncratic causes, but still incisively self-critical, then presented his favored interpretation, honestly recognizing its basis in a comforting view of life that could not be proved:

I cannot deny that this second view, the anthropic principle, is a
possible
interpretation of the evidence, although I favor the first explanation myself. (Always be suspicious of conclusions that reinforce uncritical hope and follow comforting traditions of Western thought.) I do not object to its presentation and discussion, so long as its status as a possible interpretation, not a logical inference, receives proper identification—as Wallace did eighty years ago, and Dyson did not in our own time. I, for one, will seek my hope elsewhere. I would also be surprised, but not in the slightest displeased, if,
mirabile dictu
, Wallace and Dyson were right after all.

Postscript

Several readers informed me (as I should have remembered) that Mark Twain’s famous essay, “The damned human race,” was written as an explicit response to Wallace’s version of the anthropic principle. Part 1 of this series, entitled “Was the world made for man?,” carries as its epigraphic quote: “Alfred Russell [sic for Russel] Wallace’s revival of the theory that this earth is at the centre of the stellar universe, and is the only habitable globe, has aroused great interest in the world.” Twain, in his inimitable manner, then retells the history of life in five pages, assuring us that all the rich and unpatterned diversity could only represent a long pageant of preparation for that geological final second of human habitation!—so much for Wallace’s assertion that the universe must have been designed with us in mind.

I was fascinated to read how many other themes of these essays lie embedded in Twain’s succinct satire. For example, he explicitly cites Kelvin as his authority for the earth’s
great
age—an affirmation of my argument (see essay 8) that Kelvin’s work, in his own day and contrary to the common myth portraying him as an arrogant villain against empirical science, was interpreted as proof of the earth’s comfortable antiquity, not as a constraint upon the immensity of time: “According to these [Kelvin’s] figures, it took 99,968,000 years to prepare the world for man, impatient as the Creator doubtless was to see him and admire him. But a large enterprise like this has to be conducted warily, painstakingly, logically.”

Mark Twain’s ending presents a wonderful metaphor (literature and popular science contain so many) for the earth’s great age relative to the length of human habitation. (I view it as a kind of literary ancestor to John McPhee’s image in
Basin and Range
—that if we envision geological time as the old English yard, the distance from the King’s nose to the tip of his outstretched arm, one stroke of a file applied to the nail of his middle finger would erase all of human history):

SINCE THE STUDY
of extraterrestrial life lacks any proven subject, opinions about the form and frequency of nonearthly beings record the hopes and fears of speculating scientists more than the constraints of evidence. Alfred Russel Wallace, for example, Darwin’s partner in the discovery of natural selection and the first great evolutionist to consider exobiology in any detail, held firmly that man must be alone in the entire cosmos—for he could not bear the thought that human intelligence had not been the uniquely special gift of God, conferred upon an ideally suited planet. He wrote in 1903 that the existence of abundant and brainy extraterrestrials “would imply that man is an animal and nothing more, is of no importance in the universe, needed no great preparations for his advent, only, perhaps, a second-rate demon, and a third or fourth-rate earth” (see previous essay for a full version of this quotation and discussion of Wallace’s views).

The endless debate about extraterrestrial life has focused upon the calculation of probabilities—how many stars, how many suitable planets, the chance that life will originate on appropriate earths, the probability that life will eventually generate intelligence. I must confess that I have always viewed this literature as dreary and inconclusive, too mixed up with hope and uncertainty to reach any respectable conclusion.

Recently, several astronomers and astrophysicists have advocated a different approach—a direct search for the technological byproducts of intelligence by scanning the skies systematically with radiotelescopes, probing for signals emitted by other civilizations. This so-called SETI program (
s
earch for
e
xtra
t
errestrial
i
ntelligence) has been vigorously debated. Proponents claim that it would require but a minute fraction of the annual NASA budget and, whatever its chances of success, would at least move the subject from fruitless debate about probabilities to an experimental probe by the only means now available. Opponents counter that the scheme is a boondoggle, still costing millions and so virtually assured of failure that it merits not a penny of sparse public funds for science.

As an evolutionary biologist, I have no expert knowledge in most areas motivating this debate. I am moved to comment only because opponents of SETI have featured an argument from my field as one of their most powerful weapons. They state that all leading evolutionary biologists have proclaimed the existence of extraterrestrial life as nearly inconceivable. The optimism of some physical scientists therefore resides in their failure to understand the distinctive character of evolutionary reasoning. But opponents of SETI have misstated the biological argument, and I would like to explain why at least one evolutionary biologist thinks that SETI is a long shot well worth trying.

Frank J. Tipler, a mathematical physicist from Tulane University, has been the most indefatigable critic of SETI. In a long series of strongly worded articles for both technical and popular journals (
New Scientist, Mercury, Physics Today, Quarterly Journal of the Royal Astronomical Society
, for example), he gives “two basic reasons for my disbelief in the existence of extraterrestrial intelligent beings” (all quotes from his 1982 article in bibliography, though Tipler pursues the same themes in all his writings on SETI).

The second reason lies outside my field and I shall not dwell on it, though it must be mentioned. Tipler argues that “if ‘they’ existed, they would already be here…. Because they are not here, no such beings exist.” In short, Tipler claims that any truly intelligent creatures would search or colonize the cosmos with a device that he calls a von Neumann machine—“a computer with intelligence close to the human level, capable of self-replication and capable, indeed, of constructing anything for which it has plans, using the raw materials available in the solar system it is aimed at.” Intelligent life could therefore explore an entire galaxy “for the price of one von Neumann machine”—for this computer would mine asteroids and comets for material to build replicas of itself and its enclosing probe. These replicas would then scurry off to other suitable stars and replicate again. In a mere 300 million years, a whole galaxy could be saturated with the duplicated products of one von Neumann machine.

Such a machine could even fabricate the flesh and blood of extraterrestrials by mining the needed chemicals and then running the genetic program of its creator from stored memory:

I don’t mean to be a philistine, but I must confess that I simply don’t know how to react to such arguments. I have enough trouble predicting the plans and reactions of people closest to me. I am usually baffled by the thoughts and accomplishments of humans in different cultures. I’ll be damned if I can state with certainty what some extraterrestrial source of intelligence might do. Thus, Tipler’s second argument follows the speculative tradition that SETI, with its experimental approach, is designed to transcend.

As his first argument, however, Tipler features a different kind of claim based on the methods and data of my field. He writes:

On the most mundane level, if I may play the irrelevant “expert game” for just one sentence, Tipler’s statement is empirically false. I count at least four quite respectable evolutionists in the international pro-SETI petition recently released by Carl Sagan (Tom Eisner of Cornell, Dave Raup of the University of Chicago, Ed Wilson of Harvard, and with apologies for arrogance, yours truly). Evolutionary biologists, in their usual consistency with nature’s primary theme, maintain a
diversity
of views on this subject.

More importantly, I think that Tipler has misunderstood what evolutionary biologists dismiss with such forcefulness by conflating two very different issues. All evolutionists who have discussed exobiology at length have clearly delineated two separate concerns—a specific claim and a general argument.

The
specific
issue considers
detailed repeatability
of any particular evolutionary sequence—in this case the evolution of creatures looking pretty much like us: bilaterally symmetrical with sense organs up front, two eyes, a nose in the middle, a mouth, and a brain. If we could start the earth’s tape anew, would intelligent creatures evolve again in this form? If other worlds share our basic chemistry and conditions, would such “humanoids” evolve on them?

The
general
question asks whether attributes that we would identify as intelligence might arise in creatures of any conformation—blobs, films, spheres of pulsating energy, or diffuse and unimagined forms far beyond the limited visions of most science fiction writers.

All evolutionists have vociferously denied the specific claim, and I join them in all their vigor. Many evolutionists have also gone a step further to doubt the general argument as well, but never with such certainty—and always as a personal opinion, not as a proclamation bearing the indelible imprimatur of “evolutionary theory.” I stand among those evolutionists who deny the specific claim but feel that no strong opinion can be entertained about the general argument. SETI only needs the general argument to bolster its case for support.

Gregory Bateson, the recently deceased guru of sciences that deal with complex objects and interacting systems, often emphasized that confusion of hierarchical categories may be the most common and serious fallacy of human reasoning (see his book
Mind and Nature
, for example). As a primary example of “category confusions,” Bateson identified the substitution of individuals for classes (or vice versa).

Casey Stengel, one of the greatest general gurus of our time, consciously committed Bateson’s fallacy of categories to avoid the heat of scrutiny in a tough moment. He was roundly criticized for blowing the Mets’s first pick in the expansion draft on a
particular
catcher of quite modest ability (one Hobie Landrith by name). Casey answered by invoking the
class
of catchers in general—“You have to have a catcher, because if you don’t, you’re likely to have a lot of passed balls.” Now Ol’ Case, as usual, knew exactly what he was saying (never let the patter known as “Stengelese” fool you). He used humor to blunt criticism because he knew that we would all recognize the fallacy of reasoning and laugh at the conflation. But we commit the same error in subtler circumstances and fail to identify our confusion.

When we use “evolutionary theory” to deny categorically the possibility of extraterrestrial intelligence, we commit the classic fallacy of substituting specifics (
individual
repeatability of humanoids) for classes (the probability that evolution elsewhere might produce a creature in the
general
class of intelligent beings). I can present a good argument from “evolutionary theory” against the repetition of anything like a human body elsewhere; I cannot extend it to the general proposition that intelligence in some form might pervade the universe.

Physical scientists, following the stereotype of science as a predictable, deterministic enterprise, have often reasoned that if humans arose on earth, then we must infer (since cause leads inexorably to effect) that intelligent creatures of roughly human form would arise on any planet beginning with physical and chemical conditions similar to those that prevailed on the early earth. Perhaps this deterministic outlook is responsible for the paltry imagination of film makers and science fiction writers, with their endless creatures, all designed on a human model with two eyes, a nose, a mouth, two arms, and two legs (
Close Encounters, ET
, and even the more imaginative
Star Wars
). This tendency could be forgiven when human actors had to play the roles in our movies, but now that pieces of plastic can evoke our deepest emotions and move so subtly that ET becomes a national hero, this excuse no longer holds.

But styles of science are as diverse as their subject matter. Classical determinism and complete predictability may prevail for simple macroscopic objects subject to a few basic laws of motion (balls rolling down inclined planes in high school physics experiments), but complex historical objects do not lend themselves to such easy treatment. In the history of life, all results are products of long series of events, each so intricately dependent upon particular environments and previous histories that we cannot predict their future course with any certainty. The historical sciences try to explain unique situations—immensely complex historical accidents. Evolutionary biologists, as historical scientists, do not expect detailed repetition and cannot use the actual results of history to establish probabilities for recurrence (would a Caesar again die brutally in Rome if we could go back to
Australopithecus
in Africa and start anew?). Evolutionists view the origin of humans (or any particular butterfly, roach, or starfish) as a historical event of such complexity and improbability that we would never expect to see anything exactly like it again (or elsewhere)—hence our strong opposition to the
specific
argument about humanoids on other worlds. Consider just two of the many reasons for uniqueness of complex events in the history of life.

1. Mass extinction as a key influence upon the history of life on earth
   (see essays in section 8). Dinosaurs died some 65 million years ago in the great worldwide Cretaceous extinction that also snuffed out about half the species of shallow water marine invertebrates. They had ruled terrestrial environments for 100 million years and would probably reign today if they had survived the debacle. Mammals arose at about the same time and spent their first 100 million years as small creatures inhabiting the nooks and crannies of a dinosaur’s world. If the death of dinosaurs had not provided their great opportunity, mammals would still be small and insignificant creatures. We would not be here, and no consciously intelligent life would grace our earth. Evidence gathered since 1980 (see essay 29) indicates that the impact of an extraterrestrial body triggered this extinction. What could be more unpredictable and unexpected than comets or asteroids striking the earth literally out of the blue? Yet without such impact, our earth would lack consciously intelligent life. Many great extinctions (several larger than the Cretaceous event) have set basic patterns in the history of life, imparting an essential randomness to our evolutionary pageant.
   
2. Each species as a concatenation of improbabilities
   . Any animal species—human, squid, or coral—is the latest link of an evolutionary chain stretching through thousands of species back to the inception of life. If any of these species had become extinct or evolved in another direction, final results would be markedly different. Each chain of improbable events includes adaptations developed for a local environment and only fortuitously suited to support later changes. Our ancestors among fishes evolved a peculiar fin with a sturdy, central bony axis. Without a structure of this kind, landbound descendants could not have supported themselves in a nonbuoyant terrestrial environment. (Most lineages of fishes did not and could not evolve terrestrial descendants because they lacked fins of this form.) Yet these fins did not evolve in anticipation of future terrestrial needs. They developed as adaptations to a local environment in water, and were luckily suited to permit a new terrestrial direction later on. All evolutionary sequences include such a large set of
   sine quibus non
   , a fortuitous series of accidents with respect to future evolutionary success. Human brains and bodies did not evolve along a direct and inevitable ladder, but by a circuitous and tortuous route carved by adaptations evolved for different reasons, and fortunately suited to later needs.