SETI: A Critical History
Part II Expanding the ETI discourse
Chapter 6. The evolutionists' critique of SETI
Is it possible to call a book about extraterrestrial
– I. S. Shklovskii
The application of this method is essentially an act of faith.
– Carl Sagan
Evolutionists have expressed doubts about the existence of extraterrestrial
intelligences (ETIs) since there have been evolutionists. They initially
voiced their skepticism from within the traditional ETI discourse; i.e.,
they assumed ETIs are necessarily humanoid and offered a rationale for why
humanoids were unlikely to evolve again. Around the middle of the 20th century,
after a comprehensive review and consolidation of evolutionary thought known
as "the modern synthesis," evolutionists reaffirmed their traditional skepticism
about humanoid ETIs. The laws of probability virtually ruled out a repetition
of the enormous number of twists and turns in the extremely long evolutionary
path that produced human intelligence. (See evolutionary
theory and extraterrestrial life.)
A different enormous number struck astronomers, including SETI's founders.
Observational and theoretical breakthroughs regularly led astronomers to
increase their estimate of the size of the known universe, and by the 1960s
they homed in on the estimates in use today. In rough terms, astronomers
believe something like 100 billion stars are in each of 100 billion galaxies.
Astronomers tend to be as impressed by the vast number of possible sites
on which intelligence might evolve as evolutionists are impressed by the
vast number of twists and turns in the evolutionary path that produced it
here on Earth. Where the evolutionists saw impossibility the astronomers
saw probability, and it is unsurprising that the two fields developed decidedly
different opinions about whether ETIs exist.
In addition to arguing against the possibility of humanoid ETIs, evolutionists
were, concurrently with the Soviets, instrumental in amplifying the ETI
discourse to incorporate the idea that non-humanoid ETIs might exist. The
evolutionists used both arguments – the unlikelihood of humanoid intelligence
and the possibility of non-humanoid intelligence – to critique SETI’s
SETI's proponents ignored the possibility of non-humanoid ETIs but acknowledged
the evolutionists' traditional criticism; Carl Sagan
tried to neutralize it by expanding SETI-Science to include what he called
his "quasi-ergodic theorem."
The co-founder of the theory of evolution by natural selection, Alfred Russel
Wallace, was the first evolutionist to express
skepticism about the existence of ETIs. Writing around the turn of the 20th
century, he disputed Percival Lowell's claims
of humanoid Martians. Some of Wallace's critics conceded that ETIs might
not exist in our solar system, but argued that the large number of stars,
at least some of which presumably had planetary systems, represented too
many venues on which humanoid ETIs might have evolved for Earth to be unique.
By 1903 Wallace specifically rejected that claim, too. He based his response
on a number of arguments, but primarily on his opinion that the evolutionary
path which produced our species was so long and so complex that its repetition
elsewhere was "infinitely improbable."
Wallace came intriguingly close to suggesting the possibility of non-humanoid
ETIs. "Of course it may be said that a creature with a mind and spiritual
nature equal to that of man might have been developed in a very different
form." He ultimately failed, however, to acknowledge the possibility of
a being with a different cognitive structure, consciousness, or intelligence.
A half-century passed before an evolutionist did so. Writing in 1921, the
biologist William Diller Matthew observed
that biologists and astronomers tended to think about the significance of
"the innumerable multitude of stars" in ways that reflected the "frame of
mind" of their field. The astronomer, more accustomed to dealing with problems
that can be solved mathematically, concluded that the "laws of chance" favored
the evolution of intelligent life elsewhere. The biologist, on the other
hand, thought historically and was thus more keenly aware of the improbability
of repeating any given evolutionary path.
Wallace and Matthews knew full well that their critics based their rationale
on the idea that the universe is a very large place, with lots of opportunities
for life to originate and for ETIs to evolve. The generation of astronomers
that included SETI's architects believed the universe to be an even larger
place than was thought when Wallace and Matthews published their views.
By mid-century the astronomer Sir Harold Spencer
Jones concluded, as we saw, that, "with the Universe constructed on
so vast a scale, it would seem inherently improbable that our small Earth
can be the only home of life." When SETI appeared the dimensions of the
ETI debate were framed by Wallace's evolutionist's claim that the development
of intelligence was "infinitely improbable" and Jones' astronomer's claim
that it was "inherently improbable" that terrestrial life was unique.
To illustrate with a conventional example how both sides thought about the
problem, note the very small probability that, when tossing a coin, it will
land heads-up ten thousand times in a row. Wallace meant something like
this when he said a repetition of human evolution is "infinitely improbable."
Although very small, this probability is, nonetheless, greater than zero.
And if a coin was tossed a number of times that corresponded to the number
of stars in the known universe, hundreds of billions of billions of times,
it actually becomes statistically probable that, somewhere along
the line, there would be ten thousand consecutive heads. As Drake's boss
at Green Bank, Otto Struve, said the year
of Drake's first SETI search, "an intrinsically improbable single event
may become highly probable if the number of events is very great."
This difference in the significance attached by astronomers and evolutionists
to very large and very small numbers was one of the few challenges to SETI's
assumptions aired in the academic literature. It appeared in a variety of
scientific journals with what must have seemed to SETI's sponsors like irritating
regularity. Indeed, it has continued into the twenty-first century.
Until around the time of the Second World War evolutionists from the different
branches of science tended to operate in independent silos. Then, inspired
in large part by new insights into the mechanics of natural selection provided
by the rapidly developing field of genetics,
evolutionists from these different fields began to re-evaluate their own
thinking in the light of the thinking of their colleagues from other fields.
The so-called "modern synthesis" in evolutionary thinking emerged from this
burst of creativity, an event that "gave evolutionary biologists a new self-confidence."
The ETI discourse benefited directly. A number of scientists who played
prominent roles in the formation of the Society for the Study of Evolution,
the institutional voice of the synthesis, also contributed to the ETI discourse,
including George Gaylord Simpson, Theodosius
Dobzhansky, and Ernst Mayr. Indeed, the
field generally brought distinction to itself for the contributions it volunteered
to the discourse, especially as critics and agents of change. In particular,
these evolutionists pioneered the expansion of the ETI discourse beyond
its construction around the single question of whether ETIs exist. They,
like their contemporaries on the Soviet CETI
team, were among the first to problematize the nature of ETI. From this
new platform these experts questioned some of the most important assumptions
of SETI-Science and the SETI project itself, and eventually even the motives
of SETI's architects.
Eiseley: the possibility of non-humanoids
In 1953, the year of Sagan's epiphanous encounter with Stanley Miller's
experiment (see Miller-Urey experiment),
the anthropologist Loren Eiseley wrote an
unusually prescient article in Harper's Magazine. He reflected
that "we now talk, write, and dream endlessly of space rockets" and that
people's thoughts naturally turned to the topic of ETIs. Borrowing Wallace's
argument that it was "infinitely improbable" that our evolutionary history
would be repeated elsewhere, Eiseley came down decisively against the idea
of humanoid ETIs. The evolutionist reached the often-quoted conclusion that,
"Of men elsewhere, and beyond, there will be none forever."
Eiseley also made the conceptual leap that Wallace did not. Although the
evolution of "men" elsewhere was unlikely, Eiseley raised the possibility
that non-humanoid ETIs might evolve. Indeed, one struggles
to find a scientist who so calmly contemplated the prospect of non-humanoid
ETIs since Fontenelle almost three hundred
years earlier. "Nowhere in all space or on a thousand worlds will there
be men to share our loneliness. There may be wisdom; there may be power;
somewhere across space great instruments, handled by strange manipulative
organs, may stare vainly at our floating cloud wrack, their owners yearning
as we yearn."
Eiseley made a critical contribution. As long as evolutionists simply weighed
in on the question of whether or not humanoid ETIs exist, they
essentially reinforced the traditional ETI discourse, even when disputing
the idea that humanoid ETIs might evolve. However, once non-humanoid
ETIs became a possibility, the discourse became significantly more complex.
Commentators no longer addressed the binary question of whether just one
kind of ETI existed. A whole new world of possibilities opened up.
Simpson: making SETI's assumptions overt
A decade after Eiseley's essay the paleontologist George Gaylord Simpson
directly criticized NASA's SETL projects which, after the Green
Bank meeting two years previously, potentially included SETI. Simpson
repeated the core evolutionist argument laid down by Wallace and Eiseley,
that humanoid ETIs are infinitely improbable. He warned SETI's promoters
and potential backers in NASA that "the assumption, so freely made by astronomers,
physicists, and some biochemists, that once life gets started anywhere,
humanoids will eventually and inevitably appear is plainly false."
Simpson offered a definition of humanoid ETIs and thereby earned the distinction
of being the first in the ETI discourse to do so. According to Simpson a
humanoid was "a natural, living organism with intelligence comparable to
man's in quantity and quality, hence with the possibility of rational communication
with us." By providing this definition Simpson made two of SETI's most important
assumptions explicit, a year before the Soviet CETI team made the same points
at Byurakan-II. Specifically, Simpson noted that SETI assumed ETIs would
be humanoid and that communication between us would be possible.
Indeed, SETI constructed its definition of intelligence around
the ability to communicate with us. A being with whom we are unable to communicate
is, according to SETI's assumptions, not intelligent. In addition to noting
it, Simpson criticized SETI's anthropomorphism. "In the present or any foreseeable
state of our technology, the only way we could learn of other humanoids
would be by their sending us a message or actually visiting us. That requires,
in the first instance, that they must have developed manlike technology,
which by no means follows automatically from the mere development of intelligence."
Simpson ended his essay with a plea to divert government funding from space
programs, of which SETI hoped to become a part, to terrestrial science.
He charged the scientists promoting SETI and SETL with acting out of emotional
and even selfish interests. He thereby became the first, but not the last,
evolutionist to critique, not only the SETI project but also the scientists
who organized it.
Simpson exerted a profound impact on the ETI discourse. He is one of the
few critics of the SETI project that the SETI architects answered directly,
and they did so on more than one occasion. This is all-the-more noteworthy
in light of the fact that the SETI scientists never acknowledged the Soviets'
critique. One explanation for their inconsistency might be that the SETI
scientists understood evolution better than cognitive science and thus had
enough background to appreciate the issues Simpson raised. It is also possible
that the SETI scientists reacted to Simpson because they thought they had
a compelling counter-argument: they were hardly alone in arguing that the
vast number of stars suggested a vast number of possible evolutionary experiments
and a correspondingly high probability that intelligence evolved elsewhere.
As we will see, however, they responded selectively to Simpson.
The evolutionist raised two problems with SETI's assumptions: that humanoid
intelligence was unlikely to evolve again, and that non-humanoid intelligence
might evolve. The SETI scientists never responded to the second
critique. Nonetheless, all potential contributors to the ETI discourse after
Simpson had to acknowledge that a being with whom we could not communicate
was not necessarily non-intelligent, but might simply be non-humanoid.
Talking the talk
In 1964, a year after Simpson's paper, Arthur C. Clarke
and Stanley Kubrick approached Sagan. They wanted Carl Sagan's
advice on how to depict ETIs in a film they were making and eventually released
as 2001: A Space Odyssey. In Cosmic
Connection Sagan recalled that, at dinner with the pair, "I argued
that the number of individually unlikely events in the evolutionary history
of Man was so great that nothing like us is ever likely to evolve again
anywhere else in the universe. I suggested that any explicit representation
of an advanced extraterrestrial being was bound to have at least an element
of falseness about it."
This episode makes it clear that Sagan thoroughly understood the evolutionists'
critique of SETI's humanoid assumption. But if Sagan could not have the
kind of ETI he wanted – humanoids – he wanted no ETIs at all.
He recommended that Clarke and Kubrick avoid all representation of ETIs
in their film, and the filmmakers took his advice. No ETIs appear in 2001:
A Space Odyssey, one of the iconic films of Sagan's lifetime about
NASA held its first SETI conference in 1970. During the conference Sagan
again acknowledged the evolutionists' critique. Curiously, he did so using
language that Shklovskii used at Byurakan-I,
whose proceedings had been available in English translation since 1967.
Sagan referred to the "tortuous path leading to the origin of man;" Shklovskii
referred to "the long and tortuous evolutionary process of life forms."
As he did in Intelligent Life in the Universe, Sagan claimed that
"many evolutionary biologists" – he did not cite any specific references
– noted the selective advantage of intelligence, suggesting that this
essentially negated the "infinitely improbable" argument he just acknowledged.
Sagan went on to say that he was "not referring to human beings when we
discuss extraterrestrial intelligence; we are, instead, discussing a class
of much more general intelligent beings." Here Sagan once again conflated
all intelligences in an effort to establish, since humans are "intelligent,"
that all intelligent beings are humanoid, and to thereby duck Simpson's
second critique of SETI, that there might be non-humanoid ETIs.
At the same conference Sagan claimed that, without assuming anything "beyond
the assumption of our own mediocrity" one could logically conclude that
"intelligence is an inevitable consequence of biological evolution,
given enough time." [Emphasis added.] He was, of course, asking the conferees
to assume the very thing he knew evolutionists considered "infinitely improbable,"
viz. his principal of mediocrity.
The evolutionists' critique was ignored again elsewhere in this conference.
NASA invited speakers to address the topics of the likelihood that intelligence
would evolve once life arose and, if so, what forms this intelligence might
take. These were precisely the questions Simpson or any other evolutionist
might have raised, had they been invited. However, NASA did not invite evolutionists
to address these questions about evolution; they invited artificial intelligence
researchers. As we already saw, AI scientists were, like SETI's architects,
inherently biased toward the assumption that "intelligence" meant humanoid
intelligence, because that was what their project tried to artificially
Michael Arbib spoke on the "Evolution of Communicating Intelligences on
Other Planets." He confidently predicted that, "given a few billion years,
it is almost inevitable that some sort of intelligence will evolve on any
planet on which autocatalytic reactions have arisen." His rationale, while
left implicit, was straight out of SETI-Science: intelligence is a powerful
adaptation that confers significant survival value.
Arbib had not been asked to comment on the forms of that intelligence;
the next speaker, AI pioneer John McCarthy, planned to address that topic.
Nonetheless, Arbib made a number of interesting points. He mildly rebuked
Sagan for implying that intelligent life would evolve on planets.
He reminded Sagan that the physicist Fred Hoyle
depicted a scientifically plausible ETI in The
Black Cloud that evolved in interstellar space, not on a planet.
Although Arbib did not go so far as to make the points – they may
have escaped him – Hoyle's ETI was not a humanoid intelligence, and
communication with it was impossible.
Later in the conference, however, Arbib did get to the nub of the
issue raised by both the Soviet CETI team and the evolutionists, about the
difficulty of communicating with a non-humanoid intelligence. He illustrated
the point with an eloquent analogy. "It may be as difficult to communicate
our perceptions to a creature that has learned how to perceive in an alien
environment, as it is to tell a blind friend what it is like to see blue."
He even explained that mathematics, frequently
held out by SETI proponents to be a "Rosetta Stone" that all intelligent
beings shared due to uniformitarianism, might be "extremely difficult" to
communicate between beings having different cognitive structures. He followed
that comment by identifying the frailty of the anthropomorphic assumption
at the core of SETI. "Our main hope for interstellar communication is based
on the belief that a technological civilization must have numbers."
McCarthy, on the other hand, argued with SETI-Science that all intelligences
are fundamentally similar and, therefore, like our own. Again, this was
perhaps to be expected from a scientist who specialized in trying to make
machines think like humans. McCarthy used a straightforward application
of SETI-Science's principle of uniformitarianism to develop his rationale.
He claimed that "The mechanisms of intelligence are objective and are not
dependent on whether a human being or a machine or an extraterrestrial being
is doing the thinking." He reasoned that "intelligent entities in the universe
may be similar in their intellectual properties because the methods of intelligence
are determined by the problems." In other words, because beings anywhere
in the universe confronted fundamentally similar problems during their evolutionary
history, their intelligences probably evolved similarly.
Thus, from the outset of its official involvement in SETI, NASA had, at
least technically, raised the issues of whether ETIs were likely to evolve
and, if so, whether their intelligence would be humanoid. NASA heard testimony
from two highly respected scientists, Arbib and McCarthy, although their
competence to address these issues was not established. The important
point is that NASA validated SETI's core assumptions: the ETIs NASA sought
Byurakan-II: deepening the evolutionists'
critique and expanding SETI’s response
NASA did not invite evolutionists to its first SETI conference, despite
the fact that its conveners knew evolutionists raised basic questions about
the assumptions in SETI-Science. Nor did the conveners of the first meeting
of the SETI and CETI teams invite evolutionists to Byurakan-II the following
year. However, others present not only confronted the SETI scientists with
the evolutionists' critique but raised the critique to a higher level of
abstraction that challenged the very logic of SETI-Science. Sagan responded
by unveiling the first important addition to SETI-Science since its genesis
at Green Bank a decade earlier and its subsequent elaboration in Intelligent
Life in the Universe.
Byurakan-II was loosely structured along the lines of the Drake
Equation. After introductory remarks from Ambartsumyan
and Sagan, the co-chairmen, the group heard a presentation about the likelihood
of extrasolar planets. Sagan then hosted a series of presentations on the
origin and evolution of intelligent life, followed by a discussion period
that turned out to be the longest and most animated of the conference. Sagan
began by essentially asking the attendees to accept SETI-Science's principle
of mediocrity as a starting point for their discussions. "If we
are going to make some even tentative judgments on the likelihood of life
elsewhere we must decide to what extent the life we are familiar with is
characteristic of all possible life." He had successfully conducted this
same maneuver at NASA's first SETI conference a year earlier. As we saw,
that friendly audience forgave Sagan the circularity of claiming that, without
assuming anything "beyond the assumption of our own mediocrity" it was possible
to conclude that "intelligence is an inevitable consequence of
biological evolution, given enough time."
His Byurakan-II audience was not so forgiving. Francis Crick
immediately challenged Sagan's proposal, pouncing on two logical flaws in
the principle of mediocrity: the way it reasoned analogically and its use
of probability theory. Others joined Crick as the discussion proceeded.
Their challenges were serious ones, calling into question the very core
of Sagan's and the rest of the American SETI team's claim that their project
was a rigorous scientific experiment. We will examine both challenges in
Cocconi and Morrison identified
the instability of SETI's analogical base at the instant of SETI's birth.
In the first sentence of their paper they noted that our understanding of
key processes like the origin and evolution of life had not advanced to
the point where we could reliably predict whether life would arise and evolve
to intelligence elsewhere. Shklovskii repeated the point in the text that
became Intelligent Life in the Universe. Morrison's admission became
something of an embarrassment for him and his fellow SETI organizers. At
the Green Bank conference the attendees, including Morrison, did precisely
what Morrison warned against: they assigned probabilities to each of the
variables of the Drake Equation, unsupported by accepted theories. For example,
despite the fact that the process by which life first arose was –
and still is – unknown, the Green Bank attendees concluded that it
would certainly arise again elsewhere, "if the environment is favorable."
To deal with this awkward situation, Morrison engineered a subtle semantic
shift the year after the Green Bank conference. At a talk he gave to the
Philosophical Society of Washington, Morrison once again acknowledged that
our ability to think about the question of whether ETIs exist was hampered
by the fact that "we are dealing with matters in which we are at the moment
simply too ignorant to be able to characterize them with even slight reliability."
For an instant it appeared that Morrison was going to critique SETI using
his own seminal SETI article. Instead, Morrison suggested that the way to
overcome the lack of solid theoretical support was to analogize from the
one case we knew to be certain, viz., our own species. In effect, Morrison
asserted that, although we did not understand the steps involved in the
origination and evolution of intelligent life, it was logically sound to
analogize from their end result to the existence of ETIs who were, presumably,
the product of a similar, unknown, evolutionary history. Making a virtue
out of necessity, Morrison went even farther, unctuously claiming that anything
other than extrapolating from this one example was irresponsible. "No more
imaginative discussion! Everything from now on is done with analogies of
the most timid kind, avoiding any serious extrapolations."
When Crick objected to Sagan's use of the principle of mediocrity at Byurakan-II
he used the argument first made by Morrison: that one cannot analogize from
an end state without understanding the causal steps that produced that end
state. "It is not possible at the moment, with our [lack of] knowledge of
biochemistry to make any reasonable estimate whatsoever of" the probability
that life arose elsewhere.
Sagan called Crick’s comments "provocative," but in fact it was Sagan who
was being provocative. As early as 1966, in one of his annotations in Intelligent
Life in the Universe, Sagan acknowledged that, in the context of ETI,
"it is dangerous to extrapolate from one example." He conceded that "the
application of this method to areas where we have little knowledge is essentially
an act of faith." Indeed, the principle of mediocrity did seem to be a kind
of article of faith for Sagan. Later in the conference, during the long
and animated discussion that followed the presentations on the origin and
evolution of intelligent life, Sagan became testy over the participants'
reluctance to cede any credence at all to his cornerstone assumption of
mediocrity. He found it incredible that no one was willing to agree with
him that the fact that intelligent life arose on Earth was a factor weighing
in favor of its evolution elsewhere. Surprisingly, even Morrison failed
to lend Sagan any support, despite the fact that years earlier Morrison
argued that doing otherwise was irresponsible. In a moment of exasperation
Sagan asked, "If one case is not relevant I wonder how many cases are necessary
before we get relevance?"
Crick immediately shot back, "Two."
Sagan went on to tell the Byurakan-II conferees that they would face the
same problem when they discussed the rest of the Drake Equation variables.
This was a curiously self-defeating remark. Sagan obviously had trouble
conceiving that analogizing from a known example, even if it was a single
example, was anything other than self-evidently logical. He worried that
if his colleagues were not prepared to agree on that, their ability to agree
on anything would be compromised. He was soon proved right.
In addition to his claim that Sagan's basing the principle of mediocrity
on one example was analogically weak, Crick also criticized Sagan for violating
the principles of probability theory. He likened mediocrity to the claim
that if, during a card game, we were dealt a certain hand, in a certain
order, then that sequence of cards was not an unlikely event, simply by
virtue of the fact that we happened to have it. It is, of course, highly
unlikely that any specific hand – say a straight in poker consisting
of the four of spades, the five of hearts, the six of spades, the seven
of diamonds, and the eight of clubs – will be dealt, especially in
that exact order.
The University of Chicago historian William McNeill, whom we encountered
previously at this conference defending the Soviet critique of a SETI-style
search, took up Crick's challenge again as soon as the group began their
discussion period after the presentations on the origin of life and the
evolution of intelligence. He called Sagan's "master formula," a reference
to the Drake Equation, "perhaps a little arbitrary." McNeill argued that
the Drake Equation had too few terms. Instead of a handful of probabilities
of sweeping breadth, such as the probability that life originates, McNeill
thought it logically sounder to have a larger number of more discrete probabilities.
He suggested, for example, that the equation might want to introduce the
probability that plant life arises and, only then, the probability that
animal life arises.
McNeill acknowledged the bleak consequences of his recommendation: the more
variables one added, the smaller the probable number of ETIs became. This
is because each new variable will have a probability of less than 1.0 and,
when multiplying the component probabilities out, the more probabilities
there are that are less than 1.0, the lower the product, N, or
the number of ETIs.
McNeill had, of course, backed into the "infinitely improbable" argument
of the evolutionists. The new insight he offered was that the reasoning
behind the Drake Equation might be flawed. Using only a priori
logical and mathematical reasoning, i.e., making no references to fossil
evidence or the process of natural selection, McNeill concluded that the
Drake Equation oversimplified what occurred during evolution.
Sagan disagreed with McNeill. His reasons were, at first, obscure. He rhetorically
asked, "Is there a kind of quasi-ergodic theorem in the evolution of civilizations
so that you will always wind up, by some path or other, in that particular
area of intellectual development? If so, it might be perfectly acceptable
to have many of the [Drake Equation probabilities] equal unity."
Shklovskii's ears perked up. Had Sagan just suggested that there was a theoretical
reason to suppose that evolution would always produce intelligence?
Shklovskii had been silent until that point and was silent for the remainder
of the discussion; he thereby drew particular attention to his one question.
"Could Doctor McNeill repeat his problem?" Shklovskii asked his question
to emphasize the contrast between McNeill's point and Sagan's claim, not
because he did not understand McNeill. Shklovskii was no stranger to the
evolutionists' critique. He told his Soviet colleagues at Byurakan-I seven
years earlier, "The following question is of great importance: is intelligence
an inevitable consequence of the long and tortuous evolutionary
process of life forms? In my opinion, this is by no means so. Moreover,
we should take account of the fact that the probability of intelligent life
forms developing on any given planet is exceedingly low." [Emphasis added.]
Whereas Shklovskii thus introduced this bias – the evolutionists'
critique – into Soviet thinking about CETI at its first meeting, at
their first meeting the American Green Bank participants had ignored
the evolutionists' critique by assigning probabilities of "about unity"
to the Drake Equation variables dealing with the origin of life and the
evolution of intelligence.
McNeill repeated his problem for Shklovskii, essentially restating the evolutionists'
"infinitely improbable" point. Sagan tried to deflect the challenge by acknowledging
it head on. "Let me say what Simpson’s view is." He recounted the "infinitely
improbable" argument faithfully. Sagan failed, however, to represent Simpson's
views about the possibility of non-humanoid ETIs and the difficulties of
communicating with them.
Then Sagan introduced a new tenet of SETI-Science, one that was designed
to refute Simpson and the other evolutionists. It was the first enhancement
of SETI-Science since he introduced uniformitarianism in Intelligent
Life in the Universe five years previously. He claimed that the improbability
of repeating humans' evolutionary history is offset by the very large number
of possible evolutionary paths to any given end point, such as humanoid
intelligence. This was the "quasi-ergodic theorem" he had in mind earlier.
"And that is precisely what I think the criticism of Simpson's view is –
that there may be many, many other pathways to an organism which is functionally
equivalent to a human being ..."
Sagan asked Leslie Orgel, an American expert
on the origins of nucleic life, to recap their "rather unstructured discussion."
Orgel did so and further impressed on the participants that "we really have
to deal with this question because we can't go away in a totally agnostic
mood saying that really it is not possible to do anything because we don’t
know anything." Orgel understood that if some kind of resolution to these
key issues of how to construct sound analogies and use probability theory
could not be found, it would be difficult to justify a SETI-style search.
Bernard Oliver tried to lend support to Sagan's
claims. He made SETI-Science's convergence argument, claiming that intelligent
communication had arisen more than once right here on Earth. Oliver
tried to convince his audience that the difference between the "speech"
of birds and human speech "is a question of degree and abstractness, not
of existence or nonexistence." Then, in an apparent attempt to confirm Sagan's
"quasi-ergodic theorem" by refuting its negative, Oliver pointed out that
if we assessed the probabilities that each of our ancestors mated, we would
conclude that we were impossible. Neither argument drew a response.
Morrison, playing the elder statesman, tried to end the discussion on a
constructive note. He declared that the proponents of competing positions
had eloquently stated their positions, and that "if there is anything more
to be said about these probability arguments, it can be said by the probability
theorists." However, even as he tried to dismiss the issue Morrison only
managed to draw more attention to it. He categorized the issues that had
been raised as "probability arguments." It is true that Crick claimed that
mediocrity was based on a flawed use of probability theory. But Morrison
apparently forgot that Crick also questioned Sagan's use of analogical thinking.
There were two challenges to the fundamental logic of SETI-Science
on the table. Shklovskii was about to add a third.
The next session was on the key variable of the Drake Equation, L,
or the lifetime of a technical civilization (see lifetime
of extraterrestrial civilizations). Shklovskii had been assigned the
job of lead speaker. As he began his remarks he made it clear that the discussion
that had just ended still weighed heavily on him. As noted, he remained
virtually silent during the discussion. Perhaps he needed the time until
now to formulate his reaction. In any event, instead of introducing his
assigned topic he dropped a bombshell. "I have some difficulty defining
the subject of our symposium." He went on to remind the conferees that "all
the natural sciences rely on observations and experiments," and that scientific
postulates "are generalizations of experimental findings." Shklovskii noted
that SETI did not follow these basic principles of the scientific method.
Instead, its postulate that ETIs exist "rests on logic alone." In other
words, SETI-Science did not begin with observations, from which generalizations
– theories – were formulated and tested. SETI looked for
observations. SETI-Science reversed the traditional process of the scientific
method. Shklovskii pointed out that SETI was thus similar to geometry in
its reliance on a priori assumptions. "But I think that even the
most faithful among us are not as convinced of [the existence of ETIs] as
the experts in geometry have always been convinced of the fact that parallel
lines do not meet."
Shklovskii, like Crick and McNeill, was questioning the very logic used
to construct SETI-Science. The SETI scientists, especially Sagan, should
not have been surprised. In Shklovskii's original text that Sagan re-fashioned
into Intelligent Life in the Universe Shklovskii wrote that, "It
would seem, then, that this book is concerned with an unsolved – if
not unsolvable – problem. Is it in fact possible to call a book dealing
with intelligent life in the universe 'scientific?'"
If any doubts remained about whether SETI-Science's methods, down to the
core of how it constructed its most basic propositions, had been dealt a
serious blow at Byurakan-II, they were erased by the time the proceedings
of the meeting were published. When editing the proceedings, Sagan followed
Morrison's suggestion and turned the arguments over to a probability theorist,
Terrence Fine, who worked with Sagan at Cornell. Sagan included Fine's response
as an appendix. Fine explained that there are a number of "interpretive
bases" accepted by probability theorists. "The frequency interpretation
is the most widely espoused in the sciences," and is the familiar numerical
probability that, e.g., a tossed coin will land heads-up. Fine went on to
say that "It is evident that the frequency conception has no bearing on
the issues currently raised by the question of" SETI.
Fine then explained that there was another kind of probability,
"subjective interpretation [that is] a largely unassisted process of introspection."
He explained that probability estimates can be made using this method; however,
they are not designed to assess the truth of a proposition but to select
"optimal decisions or acts, such as the allocation of research resources."
Given the status of SETI-Science at that time, Fine judged that "the concept
of subjective probability is at present the only basis on which probability
statements can be made about [ETI]."
A probability theorist thus affirmed Crick's critique. Although the combination
of Fine's formal language and the fact that Sagan buried it in an appendix
obscured its significance, the evolutionists' critique of SETI's key assumption
of mediocrity did enter the record of Byurakan-II's proceedings. It was
finally acknowledged that the idea that ETIs would be humanoid was the product
of "a largely unassisted process of introspection."
Around the time of NASA's first SETI conference, the NAS conducted a survey
of biologists from around the world to assess their views on a variety of
topics. The geneticist Theodosius Dobzhansky was among the 175 scientists
surveyed. One finding of the survey was that the group believed "a serious,
well-funded search for extraterrestrial signals should be organized on a
worldwide basis." Dobzhansky objected to this conclusion and felt moved
to respond. He disparaged his colleagues who argued for the existence of
humanoid ETIs. "Cosmologists and exobiologists ... who speculate on this
topic assume lightly that the development would be on the whole like that
of life on Earth. The climax predicted with astonishing confidence is the
emergence of humanoids, manlike rational beings ...."
In his essay Dobzhansky updated the "infinitely improbable" argument, explaining
it, not in terms of the number of branches in natural selection's path but
in terms of the improbability that the allele combinations of contemporary
humans would be selected again, even if evolution elsewhere produced the
genetic equivalent of beings as similar to us as our direct ancestors in
the Eocene era.
The theme Dobzhansky really wanted to develop in this essay was the mistake
made by many, especially non-biologists, of ascribing determinism
to natural selection. A number of SETI's
pioneers were regularly guilty of the kind of teleological thinking that
Dobzhansky warned against. For example, at NASA's first SETI conference
Drake claimed that "it appears that some aspects of evolution have always
progressed towards certain ends. One of these ends, the one that is most
relevant to us, is intelligence." In another case, a report prepared under
the supervision of Oliver and Billingham claimed that "the basic processes
of stellar, chemical, biological, and cultural evolution are universal and,
when carried to fruition, lead to technologies that must have close similarities
to ours ...."
Dobzhansky seemed to take specific aim at Sagan. During the long and heated
discussion at Byurakan-II mentioned above, Sagan became obviously exasperated
by the refusal of his colleagues to admit that the fact that humanoid intelligence
existed on the one planet they were familiar with was compelling prima
facie evidence that it was commonplace in the universe. In his article
Dobzhanksy turned Sagan's argument on its head. Dobzhansky cited the fact
that of the more than two million species living on Earth only one had evolved
language, extragenetically transmitted culture, and awareness of self and
death, as proof that it is "fatuous" to hold "the opinion that if life exists
anywhere else it must eventually give rise to rational beings."
Having exposed the dangerously deterministic inclination of SETI-Science,
Dobzhansky ended the article by essentially challenging Sagan's claim that
mediocrity was a continuation of the Copernican revolution. Dobzhansky positioned
SETI-Science's mediocrity as an over-reaction to the anthropomorphism
that prevailed until Copernicus and Darwin. "Natural scientists have been
loathe, for at least a century, to assume that there is anything radically
unique or special about the planet Earth or about the human species. This
is an understandable reaction against the traditional view that Earth, and
indeed the whole universe, was created specifically for man. The reaction
may have gone too far. It is possible that there is, after all, something
unique about man and the planet he inhabits."
Just before SETI got underway a kind of stalemate existed between the evolutionists'
contention that the evolutionary path to human intelligence contained so
many individual branching points that a repetition of their sequence was
infinitely improbable, and the astronomers' claim that the universe contained
so many potential evolutionary sites that even an event as unlikely to be
repeated as human evolution would probably recur. SETI's proponents tried
to break the stalemate by adding additional arguments to their own astronomers'
bias. SETI-Science argued that convergence proved that an adaptation like
intelligence could evolve more than once, and that intelligence conferred
so much survival value that it was likely to evolve regularly.
It held, moreover, that all evolved intelligences would be like ours because
all intelligences would be adaptations to a common set of circumstances
and problems in the universe, an idea known as uniformitarianism. Morrison
argued that the only sound analogies about ETI's possible nature
were extrapolations from the one form of intelligence known to exist; and
Sagan offered his quasi-ergodic theorem which, while acknowledging the improbability
that the exact path to human intelligence would be repeated, posited that
there are many paths to any single adaptation, such as humanoid intelligence.
The evolutionists sharpened their critique and addressed it more directly
to SETI and its architects. They called the very methods of reasoning used
by SETI-Science into question as unscientific, and criticized SETI scientists
for teleological thinking. SETI's promoters evaded a direct engagement with
the evolutionists, inviting friendlier experts to address their conferences
about the issues of the origin and evolution of intelligent life.
In the process of critiquing SETI the evolutionists became pioneers in expanding
the ETI discourse to incorporate a consideration of ETI's nature. They were
among the first to both offer a definition of what it meant to be humanoid
and to acknowledge that non-humanoid ETIs may also have evolved.
160. Alfred Russel Wallace, Is Mars Habitable?
A Critical Examination of Professor Lowell's Book "Mars and its Canals,"
With an Alternative Explanation, wku.edu/~smithch/wallace/S730.htm,
accessed 23 May 2006. See also, Alfred R. Wallace, Man's Place in
the Universe – A Study in the Results of Scientific Research in
Relation to the Unity or Plurality of Worlds, appendix to the 3rd
ed. (New York: McClure, Philips & Co, 1905), 321.
161. Wallace, Man's Place, 297–8.
162. W. D. Matthews, "Life in Other Worlds," Science 44 (1921):
163. Dick, Biological Universe, 442.
164. Probably the most compelling example is the "Rare Earth" hypothesis
promulgated by the geologist and paleontologist Peter Ward and the astronomer
and astrobiologist Donald Brownlee. In addition to the evolutionists'
"infinitely improbable" chain of evolutionary events, Ward and Brownlee
point to an improbable combination of astrophysical events that occurred
during human evolution and argue that the probability that humanoid intelligence
elsewhere is thus even lower than the evolutionists assumed. See Peter
D. Ward and Donald Brownlee, Rare Earth – Why Complex Life is
Uncommon in the Universe (New York: Copernicus/Springer-Verlag, 2000).
165. Peter J. Bowler, Evolution – The History of an Idea,
3d ed. (Berkeley: University of California Press, 2003), 326. 166. Ibid.,
167. Loren Eiseley, "Little Men and Flying Saucers," Harper's Magazine
(March 1953): 86, 91.
168. George Gaylord Simpson, "The Nonprevalence of Humanoids," in This
View of Life – The World of an Evolutionist (New York: Harcourt,
Brace & World, 1963), 253–71. See note on publication date of this essay
on page ix. Writing in August, 1963 Simpson may have had access to Pearman's
account of the Green Bank meeting.
169. Ibid., 267.
170. Ibid., 259.
171. Ibid., 269.
172. Ibid., 270.
173. Neil McAleer, Arthur C. Clarke – The Authorized Biography
(Chicago: Contemporary Books, 1992), 184; and Sagan, Cosmic Connection,
174. Carl Sagan, "An Introduction to the Problem of Interstellar Communication,"
in Cyril Ponnamperuma and A. G. W. Cameron, eds., Interstellar Communication
– Scientific Perspectives (Boston: Houghton Mifflin, 1974),
16; and Tovmasyan, 7.
175. Michael Arbib, "The Likelihood of the Evolution of Communicating
Intelligences on Other Planets," in Ponnamperuma and Cameron, 60. See
Chapter 7 for a more detailed description of The Black Cloud.
176. Ibid., 75–7.
177. Ibid., 85–7.
178. Sagan, CETI, 42.
179. Philip Morrison, "Interstellar Communication," Bulletin of the
Philosophical Society of Washington 16 (1962), reprinted in Cameron,
180. Sagan, CETI, 52.
181. Shklovskii and Sagan, 358.
182. Sagan, CETI, 146.
183. Ibid., 65.
184. Ibid., 113–9.
185. Tovmasyan, 7.
186. Sagan, CETI, 119.
187. Ibid., 129.
188. By now the dolphin example that had persuaded the Green Bank conferees
had been abandoned, due to questions about Lilly's methods.
189. Sagan, CETI, 137.
190. Ibid., 146.
191. Ibid., 147.
192. Shklovskii and Sagan, 359.
193. Sagan, CETI, 359, 361.
194. See Philip Handler, ed., Biology and the Future of Man (London:
Oxford University Press), 1970.
195. Theodosius Dobzhansky, "Darwinian Evolution and the Problem of Extraterrestrial
Life," Perspectives in Biology and Medicine 15 (Winter 1972):
196. Ponnamperuma and Cameron, 120–2.
197. This was the report of the Project Cyclops study mentioned below,
198. Sagan, CETI, 145–6.
199. Dobzhansky, 173–5.
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