the Importance of SETI for Transhumanism
of Evolution and Technology -
Vol. 13 - October
Milan M. Ćirković
Astronomical Observatory Belgrade
Volgina 7, 11160 Belgrade, Serbia and
It is argued that astrobiology in general, and the search for
extraterrestrial intelligence in particular, are of foremost
importance for the transhumanist endeavor. It is sketched how one
can show incompleteness, at best, of the arguments usually cited in
support of the uniqueness of human intelligence in the Galactic
context. In addition to the arguments conventionally cited in
support of SETI, and which can be easily cast in the form in which
their significance for the future of humanity is manifest, a
specific class of phase-transition models of development of complex
life and intelligence, suggests another powerful motivation: a very
practical issue of strategic information in the great strife for
creating values out of the Galactic material resources.
If grey-eyed Athena loved you
the way she did Odysseus in the old days
in Troy country, where we all went through so much...
Homer, cca. 800 BC
(Nestor to Telemachos)
It is hard to deny
that the Search for ExtraTerrestrial Intelligence (SETI; for a
recent review, see Tarter 2001) is one of the major scientific
adventures in the history of humankind. At the beginning of
twenty-first century it remains one of the oldest and most
fascinating scientific pursuits. However, SETI is just a small part
of the larger field of astrobiology, the field that is currently in
the epoch of explosive development (see beautiful recent reviews of
Des Marais and Walter 1999; Darling 2001; Ehrenfreund et al. 2002).
A host of important discoveries have been made during the last
decade or so, the most important certainly being a large number of
extrasolar planets, but also the existence of many extremophile
organisms possibly comprising “deep hot biosphere” of Thomas Gold;
the discovery of subsurface water on Mars and the huge ocean on
Europa, and possibly also Ganymede and Callisto; the unequivocal
discovery of amino-acids and other complex organic compounds in
meteorites; modeling organic chemistry in Titan’s atmosphere; the
quantitative treatment of the Galactic habitable zone (Gonzalez et
al. 2001); the development of a new generation of panspermia
theories (e.g. Raulin-Cerceau, Maurel, and Schneider 1998), spurred
by experimental verification that even terrestrial microorganisms
easily survive conditions of an asteroidal or a cometary impact;
etc. But the role of astrobiology does not end here; in the nice
phrase of Des Marais and Walter (1999), “recent discoveries create a
mandate”. The same authors continue:
astrobiology integrates key research disciplines into a program that
combines technology development, remote observation (space
missions), model building, and the extensive involvement of
educators and the public. This agenda addresses the following three
canonical questions: How does life begin and develop? Does life
exist elsewhere in the universe? What is the future of life on Earth
and in space?... Astrobiology strengthens linkages between science,
technology, and the humanities, creating an integrated view of our
world that will be beneficial for helping to define the roles that
future generations will play as stewards of our global environment
and its resources.
It would be natural
to expect that transhumanism, defined for instance as “[t]he study
of the ramifications, promises and potential dangers of the use of
science, technology, creativity, and other means to overcome
fundamental human limitations,” (http://www.transhumanism.org/resources/faq.html)
will foster a multifold interest in astrobiology. (The discussion
and conclusions of the present study apply even if we relax—as some
transhumanist thinkers deem appropriate—the qualification of “human”
in order to encompass any form of Earth-originating complex
lifeforms.) The third “canonical” astrobiological question pertains,
obviously, to transhumanist issues, but that is just the beginning
of the story. Only in comparison to other, possible or actual, life
forms do we understand and may hope to overcome our “fundamental
limitations.” One of the basic lessons of astrobiological research
is that all species are condemned to become extinct due to the
astrophysical or geophysical processes (like the cometary/asteroidal
impacts or supervolcanism), if not for other reasons (typically on
On the other hand, astrobiology also offers prospects of saving the
threatened lifeforms by discovering and investigating other
plausible habitats in the universe; in fact, if panspermia
hypotheses are correct, this has already happened many times over
the course of Galactic history. In its SETI sector, astrobiology
offers hope of glimpsing possible future courses of intelligent
civilizations, and obtaining the knowledge necessary for survival on
vastly larger spatial and temporal scales than usually considered
(Dick 2003; more on that below). In short, the mandate of
astrobiology seems, at first glance, to be the scientific basis of
precisely the transhumanist endeavor.
enough, some transhumanists seem to share the view, previously
regarded as the exclusive playground of religious (notably
Christian) fundamentalists, that intelligent life on Earth is
unique, at least in the Galactic context.
Consequently, they reject any interest in
astrobiological and SETI questions, even in the contexts in which it
directly (and possibly adversely) influences some of the basic
tenets of transhumanism. This strain of thought is expressed
particularly well, for instance, in an otherwise brilliant paper on
existential risks humanity faces (Bostrom 2001):
of running into aliens any time soon appears to be very small... If
things go well, however, and we develop into an intergalactic
civilization, we may well one day in the distant future encounter
aliens. If they were hostile and if (for some unknown reason) they
had significantly better technology than we will have then, they may
begin the process of conquering us. Alternatively, if they trigger a
phase transition of the vacuum through their high-energy physics
experiments (see the Bangs section) we may one day face the
consequences. Because the spatial extent of our civilization at that
stage would likely be very large, the conquest or destruction would
take relatively long to complete, making this scenario a whimper
rather than a bang. ...
There must be (at
least) one Great Filter – an evolutionary step that is extremely
improbable – somewhere on the line between Earth-like planet and
colonizing-in-detectable-ways civilization ADDIN ENRfu.
If the Great Filter isn’t in our past, we must fear it in our (near)
future. Maybe nearly every civilization that develops a certain
level of technology causes its own extinction.
Luckily, what we know
about our evolutionary past is consistent with the hypothesis that
the Great Filter is behind us. ... This would change dramatically if
we discovered traces of life (whether extinct or not) on other
planets. Such a discovery would be bad news. Finding a relatively
advanced life-form (multicellular organisms) would be especially
Thus, we are led
into a bizarre situation that out of all scientific
disciplines, astrobiology is the only one whose successes are not
desirable. This particularly applies to the SETI sector of the
astrobiological endeavor. To other complaints against the SETI
enterprise, one is tempted to add another: psychological welfare of
humanity, namely the need to avoid being “depressed”!
reasoning is based on an important paper of Hanson (1998), who
introduced the term “Great Filter”. Hanson presents a ladder of
steps leading from dead matter to a universe of intelligent life
colonizing the universe. These steps include physico-chemical,
biological, and socio-technological phenomena. With absence of any
manifestations of advanced intelligent life elsewhere in the
universe, we have to conclude that somewhere along the ladder we
have a “filter”, i.e. one or more steps which are very improbable.
In Hanson’s words, “someone’s story is wrong”, meaning that the
filter falls within the domain of at least one particular science
whose predictions are wrong when compared to the naive expectations.
While not completely skeptical as far as existence of
extraterrestrial civilizations is concerned, Hanson’s paper still
has at least three problematic features. The first (which
does not concern us here) is the unwarranted assumption that most
intelligent species will tend to expand and colonize throughout the
Milky Way. The second is the missing discourse on the risks inherent
in our astrobiological position (which we shall discuss in some
detail below). Notably, Hanson seems to almost entirely ignore
numerous physical factors which that can terminate or limit the
growth of life after it has already started. The third
and the most important problematic feature of Hanson’s article is
that it introduces a “see-saw” tension between the optimism for
future of human life and the optimism for life in general cosmic
Together these plausible
explanations have persuaded countless teams to construct relatively
high estimates of the probability that any one planet will
eventually produce intelligent life such as ourselves, by estimating
relatively low values for each filter term in the famous "Drake
"optimists" have taken standard economic trends and our standard
understanding of evolutionary processes to argue the plausibility of
the story I gave above, that our descendants have a decent chance of
colonizing our solar system and then, with increasingly fast and
reliable technologies of space travel, colonizing other stars and
galaxies. If so, our descendants have a foreseeable chance of
reaching such an explosive point within a cosmologically short time
(say a million years)...
While all of these stories are
at least minimally plausible, our main data point implies that at
least one of these plausible stories is wrong -- one or more of
these steps is much more improbable than it otherwise looks. If it
is one of our past steps, such as the development of single-cell
life, then we shouldn't expect to see such independently evolved
life anywhere within billions of light years from us. But if it is a
step between here and a choice to explode that is very improbable,
we should fear for our future. At the very least, our potential
would have to be much less than it seems. Optimism (as defined here)
regarding our future is directly pitted against optimism regarding
the ease of previous evolutionary steps. To the extent those
successes were easy, our future failure to explode is almost
As a consequence of
such a wide-sweeping assertion, the predominant atmosphere of
technological optimism in transhumanist (and generally educated)
circles turns easily into indifference or hostility toward SETI and
Fortunately, the situation is not necessarily so simple. In the
remainer of this paper, we shall argue that the issue of existence
and properties of extraterrestrial intelligence, as well as its
impact on the future human development, should be taken very
seriously into account in any analysis of the future of humanity.
Scepticism expressed by Bostrom is almost unwarranted even today,
when the astrobiological adventure is at its very beginning. For
instance, even the “rare Earth” hypothesis of
Ward and Brownlee (2000), which many researchers regard as being
itself rather extreme, does state that simple bacterial life is
ubiquitous throughout the Galaxy, while suggesting (the
controversial part!) that complex metazoans are indeed very rare in
the Galaxy. The advances of biochemistry and molecular biology
(which are beginning to be visible everywhere, from bathroom
supplies to the stock market) cannot fail to suggest that we are
getting closer to the understanding of the origin and underlying
mechanisms of life in a completely naturalistic manner. Similarly,
various version of computationalism (“strong AI”,
“functionalism,” etc.) are suggesting to us that
origin and underlying mechanisms of thought and intelligence itself
are eventually to be understood in a similar naturalistic manner.
SETI-scepticism amounts to the thesis—probably unique in the entire
history of science—that a completely natural phenomenon occured only
once in a vast region of space and time, while it could prima
facie occur billions of times.
2. The arguments against ETI are incomplete/wrong
The idea of
uniqueness of Earth and intelligence rests on two arguments most
frequently cited in this respect:
“Where are they?” in its modern
Carter’s “anthropic” argument.
Tsiolkovsky, Fermi, Hart, and their supporters argue on the
basis of two premises: the absence of extraterrestrials on Earth and
in the Solar System, and the fact that they have, ceteris paribus,
more than enough time in the history of Galaxy to visit, either in
person or through their self-replicating probes. Characteristic time
for colonization of the Galaxy, according to these investigators, is
106 – 108 years, making the fact that the
Solar System is (obviously) not colonized hard to explain, if not
for the absence of extraterrestrial cultures. On the other hand,
Carter’s “anthropic” argument (“argument from ignorance” would be a
better label here) tries to infer conclusions from the possible
relationships between the alleged astrophysical (t*)
and biological (tl)
In the Solar system,
within the factor of two. However, in general, it should be either
for two uncorrelated numbers. In the latter case, however, it is
difficult to understand why the very first inhabited planetary
system (that is, the Solar System) exhibits
behaviour, since we would then expect that life (and intelligence)
arose on Earth, and probably at other places in the Solar System,
much earlier than they in fact did. This gives us probabilistic
reason to believe that
(in which case the anthropic selection effects explain very well why
we do perceive the
case in the Solar System). Thus, according to Carter,
extraterrestrial life and intelligence have to be very rare, which
is the reason why we have not observed them so far.
Both (1) and
(2) are at best inconclusive, and at worst plain wrong. While a
detailed refutation is by far beyond the aims and scope of the
present paper, we shall give only a few hints, directing the
interested reader to the cited literature. First, the colonization
timescale is still largely uncertain; for instance, diffusion models
of Newman and Sagan (1981) give the relevant timescale as ~109
years, which would correspond to the naive
answer one might give on the Fermi’s question: They are still on
the way! Second, the issue of motivation of colonizers, and
particularly their von Neumann probes is much less clear and
unambiguous than the “contact pessimists” would have us believe.
Notably, as suggested by Brin (1983) in his seminal review, the
“deadly probes” scenario (the idea that the dominant
behavior of self-replicating probes is destruction of nascent
civilizations, not colonizing) is one of just a few
theoretically satisfactory explanations of the “Great Silence”. In a
similar vein, Kinouchi (2001) has recently argued that the
phenomenon of persistence, well-known from statistical physics,
holds the key for explanation of the apparent absence of
extraterrestrial civilizations; in this picture, Galactic
colonization by advanced ETIs could have already last for quite some
time without influencing the Solar System. Wilson (1994) has
persuasively criticized Carter’s usage of the anthropic principle to
show that life is rare in the universe.
But the most
important line of thought which can easily defeat both Fermi-Hart-Tipler’s
and Carter’s arguments lies in investigation of hidden temporal
assumptions in these arguments. Fermi et al. suppose that the
history of the Galaxy is uniformitarian, in the sense that advanced
technological communities could arise at any point
in the Galactic history. The exception would be, perhaps, the first
couple of billion years, when the metallicity was too low. The
seminal breakthrough of Lineweaver (2001) enables us to calculate
for the first time an age distribution for terrestrial planets,
which is not uniform in time but reaches a peak at the age of
6.4 ± 0.9 Gyr; in other words, an average terrestrial planet in the
Milky Way is almost two billion years older than Earth!
This already hints at what we wish to elaborate below: that
simplistic uniformitarianism is unwarranted in astrobiology.
Similarly, Carter assumes that the only relevant astrophysical
timescale is the Main Sequence stellar lifetime. Uniformitarianism
has not shown brightly in astrophysics and cosmology, at least since
the demise of the classical steady-state theory in the mid-1960s
(Kragh 1996). Today we are quite certain that evolutionary
properties of astrophysical systems are from time to time guided by
processes either unique (like the primordial nucleosynthesis or the
reionization of intergalactic medium),
or occuring at timescales so much vaster than the timescales of
human civilization that the probability of actually observing them
is nil (like the recently computed evolution of M-dwarf stars).
In the specific case, if the phase-transition model sketched in a
brilliant short paper of Annis (1999; see also Clarke 1981) is
correct—as we have more and more reasons to believe—the relevant
timescale is the one describing intervals between major
Galactic-wide catastrophes, precluding the
complexification of planetary biospheres and, consequently, the
development of intelligent observers. There are several plausible
candidates for this global regulation mechanism. The
strongest, as suggested by Annis in his ingenuous study, are
gamma-ray bursts (henceforth GRBs), which accompany either a
coalescence of binary neutron stars or explosions of super-massive
stars, also known as the hypernovae (for a review of GRB
mechanisms, see Piran 2000).
Astrobiological effects of GRBs have been investigated recently in a
number of papers (Thorsett 1995; Dar 1997; Scalo and Wheeler 2002),
and much of the older literature dealing with effects of supernova
explosions is useful in this case too (after scaling, of course;
see, for instance, Tucker and Terry 1968; Ruderman 1974; Clark,
McCrea, and Stephenson 1977). It seems that each GRB is surrounded
by a “lethality zone” in which its
effects are deadly for complex lifeforms (eukaryotes); according to
Scalo and Wheeler (2002). The radius of this zone is ~14
kpc, rather large in comparison to the Galactic habitable zone.
The exact effects of a GRB within a “lethality zone”
are still somewhat controversial, but it is clear
that there will be at least two deadly effects capable of causing
mass extinctions: 1. creation of nitrogen-oxides (usually denoted by
NOx) in the upper atmosphere, which will destroy
the ozone layer for thousands of years, thus enormously increasing
UV radiation at planetary surface; and 2. creation of a longer
delayed pulse of cosmic rays, which penetrate the atmosphere (and
even rocks and soil up to several km of depth) and cause various
sorts of damage to biological materials. Both these effects are
prolonged in comparison to the GRB itself, thus affecting not only
the hemisphere directed toward the source. In fact, the consequences
in biological domain may last many generations, especially when one
considers such effects as increase in frequency of cancers, and
occasionally very long interval needed for a species to die out when
its population decreases below the so-called minimum viable
population (for a popular account, see Raup 1991).
Other suggested regulation mechanisms are the climatic change due to
interaction with Galactic spiral arms (Shaviv 2002),
neutrino-induced extinctions (Collar 1996), or Galactic tides
leading to the Oort comet cloud perturbations (e.g. Clube and Napier
1990; Rampino 1998).
Their common property is that they are global, i.e.
influencing the entire Galactic habitable zone, or a large portion
of it. GRB-regulation, however, has another desirable property:
quantifiable secular evolution, which explains our own
existence at this particular epoch of the Galactic history.
Notably, cosmology suggests the rate of GRBs behaves, on the
average, as µ
with the time-constant
of the order of 109 yrs (Annis 1999). As noticed by
Norris (2000), we have to ensure that there is no “overkill”
as far as the regulation mechanisms are concerned, and that our own
existence is explicable—and not fantastically improbable!—in
naturalistic terms. This is readily achieved within the framework of
the GRB-dominated phase-transition picture: cosmology assures us
that the average rate of GRBs increases with redshift, i.e.
decreases with cosmic time. When the rate of catastrophic events is
high, there is a sort of quasi-equilibrium state between the natural
tendency of life to spread and complexify, and the rate of
destruction and extinctions governed by the regulation mechanism(s).
When the rate becomes lower than some threshold value, intelligent
and space-faring species can arise in the interval between the two
GRB-induced extinctions, and the Galaxy experiences a phase
transition: from essentially dead place, with pockets of
low-complexity life restricted to planetary surfaces, it will, on a
very short Fermi-Hart-Tipler timescale, become filled with
high-complexity life. We are living within that interval of exciting
time, in the state of disequilibrium (Almár 1992),
on the verge of the Galactic phase transition.
It is clear that this class of models effectively removes the threat
to ETIs from both Fermi-Hart-Tipler and Carter's arguments.
Elsewhere in the Galaxy there are other planets with the level of
complexity achieved more or less similar to the terrestrial one. At
each of them, a Fermi can ask his question, but that will not remove
the others from existence. There simply was not enough time for them
to come to us, since the astrobiological history—as far as complex
metazoans are concerned—is different and significantly shorter from
the history of dark matter, stars, and gas clouds which constitute
the physical structure of the Galaxy. Local astrobiological clocks
can tick at various rates, but they are all from time to time reset
by the global regulation mechanism(s). But Fermi's question is
rapidly becoming pertinent, when we realize that during the
phase transition many advanced intelligent societies are bound to
develop, but they are not all bound to expand to their utmost limits
(that is, to colonize the Galaxy) within the same interval of time.
We shall return to this important point later.
On the other hand, the very existence of well-defined astrophysical
and biological timescales is an unwarranted assumption of Carter's
argument. This assumption is wrong in the context of the
phase-transition models. The real timescales are specific to each
planetary system, depending on such factors as the location of the
system in the Galactic habitable zone (GRB distribution having a
spatial, as well as temporal aspect!), peculiarities of the local
environment (notably the density and distribution of
cometary/asteroidal material presenting the impact hazard or
quantity of radiogenic isotopes driving plate tectonics and
associated carbon recycling), and—of crucial importance—the epoch of
Galactic history. In other words, there is no physical reason why on
planet A, at galactocentric distance RA and at epoch tA
we could not have
while on planet B (characterized by RB,
tB, and probably some other astrobiological parameters)
we could have tl
The dependence on the epoch is particularly important; to paraphrase
the title of the controversial book by Ward and Brownlee (2000),
Earths might be rare in time, not in space. This sort of models
can also shed some new light on the Drake equation (Walker and
Ćirković 2003; Ćirković 2003). In other words—and to
paraphrase Homer’s “old Nestor”—it is easy enough to be wise
(intelligent) at this epoch of Galactic history, in contrast to the
3. SETI and
If we admit
insufficiency of arguments against the existence of
ETI (which, of course, does not mean that the arguments for ETI are
very strong—just that the case is completely open!), we may ask for
specification of possible important issues and benefits of SETI
projects from the transhumanist vantage point. We shall consider
three major source of relevance (and indeed importance) of the SETI
endeavor for transhumanism in some detail. The first two are rather
straightforward, to which the third one, stemming from the very
physics of phase-transition models is added.
benefits of Drake et al.
In the period of
“contact optimism” in 1960s and 1970s several beneficial aspects of
SETI projects have been listed by pioneers such as Frank Drake, Carl
Sagan, Ronald Bracewell, and others (e.g., Bracewell 1975). It was
pointed out that SETI projects are cheap and efficient, offering a
wealth of ETI-unrelated scientific data, enabling testing of
astronomical (especially radioastronomical) equipment, and serving
an important educational role. In addition, through a unique blend
of multidisciplinarity and public interest, SETI offers an excellent
avenue of communicating general scientific knowledge to the lay
public; Carl Sagan’s work on astronomy public outreach is perhaps
the most splendid example of what can be done in this respect. Stock
examples also include such difficult to quantify or intangible
benefits as the sense of unity of humankind when faced with the
vastness of space and the potential alien diversity.
There is no
need to dwell here longer on these issues, since they stand the same
today as when they were suggested. Subsequent development has only
strengthened some aspects of them: notably optical, IR, and other
SETI projects have widened the horizons for collateral scientific
benefits, and the unity of humankind certainly seems more desirable
knowledge that it is possible to pass the “Great Filter”
anthropic argument of Carter has less force than is usually assumed,
this is not tantamount to stating that the anthropic reasoning
cannot teach us important lessons about our relationship to the
physical universe. Quite the contrary: the central problem of SETI
studies can be expressed, as in Hanson (1998), as the question
“Where are we along the ‘Great Filter’?” It is overoptimistic to
state that it is behind us, and it is overpessimistic to claim that
we are at its beginning. There are important reasons to believe that
we are, in fact, somewhere in between, because while we have
overcome a lot of possible existential threats in the last couple of
Gyrs, some of them still threaten us. Notably, the threats of a
global nuclear, biotechnological or nanotechnological cataclysm,
either as a consequence of intentional or accidental misuse of these
powerful technologies still looms large. To these risks, rather
publicized in recent years, one can add other, less certain, but
potentially devastating scenarios like the abuse of AI or the
artificially triggered vacuum phase transition (the excellent
catalogue is Bostrom 2001). This spectrum of existential risks makes
some people pessimistic about our future prospects (that is the case
for instance, with Stephen Hawking, whose August 2001 interview in
“Daily Telegraph” provoked such an attention worldwide). Stock
answer to Fermi’s question for several decades—especially during the
Cold War—was exactly that: they did not get here, because they
have destroyed themselves upon the discovery of nuclear weapons.
(Today one can substitute one’s favorite doomsday technology.)
Pessimism often bears fatalism and even irresponsibility (thus, only
seemingly paradoxically, increasing the chances of disaster).
antidote for such existential pessimism would be a discovery of an
advanced ETI society or an equivalent entity.
The technical means used by such society would already give us some
idea which technologies such ETIs use—without destroying themselves.
But even without any detailed information, the very fact that SETI
succeeded will give us essential information that it is possible to
pass the “Great Filter”. On the other hand, if one does not engage
in SETI, one cannot expect success; at least until it is too late,
and here we come to the most important issue in the catalogue of
3.3. Know thy
To these rather
well-known and publicized benefits of SETI, we should now add
another, which has not actually been investigated, at least not
outside the SF circles. The main lesson of the phase-transition
models is that, starting with some epoch relatively close in our
past, the entire Galaxy is open to colonization and technologization
by whoever happens to be there, or whoever has a very
slight—in astronomical terms—advantage. Obviously,
the main purpose of colonization of the Galaxy is to use the
Galactic physical resources to create new lives, new
observer-moments, and ultimately new values. Of course, any detailed
analysis of this process hinges on what could be called
“interstellar political economy”, and in
particular the risk/benefit analysis of the
interstellar travel and colonization. For the purposes of this
cursory study we employ only those assumptions which are advanced by
“contact pessimists” in their formulation of
Fermi's paradox: that interstellar travel is physically feasible,
and at least a finite fraction of all civilizations will engage in
The period of phase transition is like a race, when after the
starting pistol goes off, many runners strive to reach the same
goal. Add to this an amount of variability of initial conditions
(runners which would not start exactly from the same starting line),
as well as inherent variability (intrinsic differences between the
ETI societies), as well as possibility of negotiations, conflicts,
and cooperation. In any of these cases, we can hardly escape to
conclude that any knowledge on our rival civilizations
gathered through SETI is an invaluable resource. This aspect of SETI
can be, very loosely, understood as a new form of (literally)
certainly and definitely does not mean that the striving for mastery
of resources on the Galactic scale should be conceived like the
ruthless grab for material power analogous to the battle of European
powers for colonies in eighteenth and nineteenth century, or inhuman
brutality accompanying the present-day fight of Western powers for
oil reserves of Middle East and Asia. It might have such a
dimension—and the considerations of existential risk in Bostrom’s
sense is applicable here—but it also can be thought as striving for
excellence and creativity in undertaking this colossal endeavor.
This can be regarded as arguably the most natural extension of the
cultural evolution on which so much within the SETI field depends
perceive—especially forcefully in this light—why Bostrom’s
lackluster treatment of possible catastrophic contact with aliens is
unsatisfactory. In some other circumstances and contexts this would
not be disturbing at all; but in the context of debates on
existential risks no loose end ought to remain.
phase-transition models offer more scope for optimism as far as
creation of values is concerned than most of the explanations of the
“Great Silence.” It suggests that the material resources of the
Galaxy simply cannot fail to be converted into values on rather
small, in astronomical terms, timescales of the future, no matter
what we, humans, decide to do. On the other hand, this sort of
optimism may sound bleak to transhumanists, since it offers no
warranty as far as the fate of humanity is concerned, in
contradistinction to pseudo-religious eschatologies, like the (in)famous
Omega-point theory of Frank Tipler. However, this is still more than
science usually offers, again in contrast to religion. To some, it
still may sound consoling that even if stupidity and irrationality
triumph here, on Earth, and we destroy or cripple ourselves, the
Galaxy will still be enriched with life, intelligence, and values.)
We conclude that
skepticism regarding SETI is at best unfounded and at worst can
seriously damage the long-term prospects of humanity. If ETIs exist,
no matter whether friendly or adversarial (or even beyond such
simple distinctions), they are relevant for our future. To neglect
this is contrary to the basic tenets of
transhumanism. To appreciate this, it is only sufficient to imagine
the consequences of SETI success for any aspect of transhumanist
interests; and then to affirm that such a success can only be
achieved without trying if they come to us, which would
obviously mean that we are hopelessly lagging in the race for
We find a streak of very subtle anthropocentrism hidden in the usual
understanding of the “Great Filter”
(as expressed by Hanson’s quote above). Seemingly, we are led into a
dilemma: either we are optimists about extraterrestrial life
and SETI or we are optimists about our particular
(human/posthuman) future. We find the dilemma false and a bit
hypocritical, like all man-as-the-measure-of-all-things argument
from Protagoras to this day. We can have both of the
alternatives above; we can be optimists about life and
intelligence in general. And only future astrobiological
research can persuasively show to which degree our optimism in both
directions is justified.
As all who
have ever tackled this question agree, investments in SETI are
invariably a minuscule fraction of any civilization’s scientific
investments. Even the cost of the most ambitious SETI projects
imagined so far (like CYCLOPS; see Oliver 1973) is negligible in
comparison to such endeavors generally regarded as desirable and
worthwhile like the development of artificial intelligence, setting
up efficient defense against impacts, or building O’Neill colonies
(not to mention more ambitious projects, like terraforming or
uplifting of stellar matter).
Thus, there is no real economic excuse for neglecting this field, as
well as the general astrobiological enterprise, once prejudices and
fallacious arguments are rejected. At least this argument applies as
long as it is really necessary to influence public opinion at large
to support this type of scientific research; it is to be hoped that
in future rich societies such research could be performed by
individuals even if the majority still continues to consider them
irrelevant or even undesirable.
all this pertains to a long-term view. No theoretical model can
guarantee the success of SETI on short timescales, certainly not on
the scale of a present-day human lifetime. But, a healthy admixture
of long-term views and long-term planning seems inescapable if we
wish to leave to our descendants a prospect of living under billion
suns of the Milky Way.
Acknowledgements. Foremost thanks belong to Robert J. Bradbury
and two referees for JET for comments which
helped immensely improved a previous version of the manuscript.
The author acknowledges Saša Nedeljković, Vesna Milošević-Zdjelar,
Ivan Almár, Olga Latinović, Branislav Nikolić, Vjera
Miović, and Milan Bogosavljević for
their kind technical help. Useful discussions of the related issues
with Nick Bostrom, Richard Cathcart, Irena Diklić, James Hughes,
Larry Claes, Fred C. Adams, Ivana Dragićević,
and Slobodan Popović are also hereby acknowledged.
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 Astrobiology comprises as a
subdiscipline the field dealing with SETI-related
studies, for which the term “xenology” is sometimes
employed (cf. Freitas 1999).
 Which leads, obviously, to one
of the best strategies of defense of technological
development against religious, ethical, or
ecological criticisms: we should invest in
development of advanced technologies, since without
them we are condemned to extinction anyway.
 It should be
noted that religious or quasi-religious views on
this issue, perhaps the last vestige of medieval
Aristotelianism, still have strong influence in the
scientific circles themselves. A particularly
amusing example is the case of Guillermo Gonzalez,
both a distinguished astronomer and Biblical
apologist, expounded in the book of Darling (2001).
Gonzalez has been a strong supporter of the
“rare Earth” theory in both his
scientific and religious writings.
 Of course, as one of the
referees has kindly pointed out, this is far from
being a monolithic attitude, and a wide spectrum of
opinions has been voiced in discussions at
conferences or mailing lists. However, rather
extreme position taken, for instance, by Bostrom
(2001) on this issue is certainly very influential,
and the debate in general and many specific
positions in particular will benefit if its
weaknesses can be clearly demonstrated.
 Another point of contact is
the relationship between SETI and AI enterprises,
which includes all attempts to eventually define
intelligence, consciousness, and related phenomena.
We shall not enter this fascinating topic here
 Stephen Webb, in his recent
monograph, so far the best historical introduction
into the “Great Silence” problem (Webb 2002), dubs
the relevant question Tsiolkovsky-Fermi-Viewing-Hart’s.
Main references are Lytkin, Finney, and Alepko
(1995; for Tsiolkovsky), Jones (1985; for Fermi),
Viewing (1975), and Hart (1975). We find it only
just to add Tipler to list, since his von Neumann
probe setup gives the whole problem completely new
flavor (Tipler 1980), although he was not, as often
mistakenly assumed, the first to propose
self-replicating machinery for interstellar contact
(e.g. Boyce 1979). Of course, it is best known
simply as “Fermi’s paradox”.
 The best comprehensive recent
treatment is the textbook of Dodelson (2003).
 For this fascinating subject
in theoretical astrophysics, see
Bodenheimer, and Adams (1997).
 In a recent abstract, Kenneth
Brecher has suggested a third possible catastrophic
effect of GRBs, namely its alleged capacity to
perturb weakly bound cometary orbits in the Oort
cloud (Brecher 1997). If it is confirmed, this will
enormously strengthen the case for GRB-mediated
global astrobiological regulation.
 The idea of Clarke (1981)
that nuclear outbursts—similar to the ones observed
in Seyfert galaxies—from the core of the Milky Way
can lead to devastation of habitable planets
throughout the Galaxy has been, historically, the
first global-regulation mechanism proposed. However,
it seems to be abandoned as we learn more about the
center of our Galaxy. (For variations—now of “only”
historical importance—on the same theme see Clube
1978; LaViolette 1987.)
 Notice that the anthropic
selection effect (cf. Bostrom 2002) readily explains
why that is so, in spite of the very low a priori
probability. Humans could not arise prior to the
phase transition, since there was no time for
high-complexity life to evolve without being
destroyed by cosmic rays and other detrimental
consequences of GRB regulation (or cumulative
effects of impacts, close SNe, spiral-arms
crossings, runaway greenhouse effect, and other
calamities). On the other hand, we could not arise
later from the phase transition epoch for the same
reason one does not expect to find a previously
unknown stone-age tribe in the present-day Europe:
high-complexity ecological niches do not allow
spontaneous emergence of new lower-complexity
 I am indebted to Robert J.
Bradbury for pointing out that the term “society”
may be too restrictive in respect to plausible
diversity of advanced stages in evolution of
intelligence in the cosmic context. The word seems
inappropriate, for instance to such entities like
the “Jupiter brains” (Sandberg 2000) or “Matrioshka
brains” (Bradbury 2001).
 One thing
should be put straight here: I use the neutral term
“rival” to denote
civilizations which may influence us in both
positive and negative (according to most established
ethical systems) manner. Thus, an advanced ETI
community may preempt human usage of (finite)
material resources of the Galaxy or exert a powerful
resistance on any human colonization of space; this
still does not qualify it as an “enemy” or even an
existential risk in terms of Bostrom (2001). On the
other hand, it is entirely conceivable that the same
advanced ETI community could manifest either a
cooperative or a submissive behavior. In any case,
it will present a powerful motivation for humanity
to exercise its best creative and cognitive
capacities, thus making a “rivalry” a very
productive one, similarly to “fair sport” model of
 I am indebted to one of the
referees for correctly pointing out that this could,
in fact, be an impediment to SETI and an explanation
of the “Great Silence” itself, since evolutionary
pressures of colonization could favor secretive and
uncommunicative races. While rather intriguing, this
option belongs to the realm of sociological (or
sociobiological) speculation which is hard to judge
at our present level of ignorance. On the other
hand, it is reasonable to assume that activities of
advanced and colonizing civilizations will be
detectable even if the level of intentional
communications is kept at minimum.
 For O'Neill's
colonies, see the original proposal in O'Neill
(1974); terraforming is discussed in numerous
papers, for instance Cathcart (1991); Fogg (1995).
For stellar uplifting see Criswell (1985).