"Intelligent Life in the Universe:
Philosophical and Theological Issues"
Robert John Russell
The Center for Theology and the Natural Sciences
The Graduate Theological Union, Berkeley, USA
(Working Draft Only)
Abstract: My presentation will focus on key philosophical
issues raised by four topics related to the scientific discussion of the
evolution of life in the universe. 1) Will life and intelligence be found
throughout the universe, or will it turn out to be exceedingly rare? 2)
Will intelligent life be capable of both rationality and moral agency? 3)
Will evolutionary biology determine its moral content or will it merely
bequeath intelligent life with moral capacity, leaving moral content to be
determined independently of biology? 4) If moral agency evolves, will
these species inevitably exhibit moral failure, or is our generic human
experience of moral failure strictly the result of our particular
evolution, leaving us to expect there to be other civilizations that are
entirely benign? The discussion of these issues, though largely
hypothetical, can offer insight into the theological and cultural
implications of the discovery of extraterrestrial intelligence as well into
a better understanding of the human condition.
Over the past four decades, there has been a striking rebirth and
expansion of the scholarly field of theology and science' and
characterized by diverse creative interactions between scientists,
philosophers and theologians. Topics in this interaction range from
comparative methodologies to theologies of creation, divine action, and
redemption in light of Big Bang, inflationary and quantum cosmologies,
quantum physics, evolutionary and molecular biology, the neurosciences,
anthropology, sociobiology, behavioral genetics, etc. Surprisingly
underrepresented in this rapidly growing interaction, however, is a focus
on the philosophical and theological issues and insights raised by the
possibility of extraterrestrial life (EL) and extraterrestrial intelligence
(ETI) in the universe. This underrepresetation is particularly curious
since historians of science have shown that the Christian theology actually
contributed in very significant ways to the assumption that ETI does in
fact exist. It is particularly timely, then, that this Sixth Trieste
Conference on Chemical Evolution includes a section on these issues.
There are, in fact, a wealth of topics which could be addressed here.
For the purposes of this short presentation, I will focus on four in
particular: 1) Will life and intelligence be found throughout the universe,
or will it turn out to be exceedingly rare? 2) Will intelligent life be
capable of both rationality and moral agency? 3) Will evolutionary biology
determine its moral content or will it merely bequeath intelligent life
with moral capacity, leaving moral content to be determined independently
of biology 4) If moral agency evolves, will these species inevitably
exhibit moral failure, or is our generic human experience of moral failure
strictly the result of our particular evolution, leaving us to expect there
to be other civilizations that are entirely benign? The discussion of
these issues, though largely hypothetical, can offer insight into the
theological and cultural implications of the discovery of extraterrestrial
intelligence as well into a better understanding of the human condition.
B. Four issues regarding ETI from the perspectives of science,
1) Will life and intelligence be found throughout the universe, or will it
turn out to be exceedingly rare?
Clearly this is one of the pivotal questions of our conference.
Hopefully, we will learn the answer by projects such as SETI and
interstellar space exploration in the reasonably near future. Such
projects, however, tend to assume that we will share modes of sensory
awareness and rationality with ETI, and this leads to two initial caveats.
First, it may be that some extraterrestrial civilizations are millions or
even billions of years older than ours. For such advanced ETI, these
contact' scenarios may simply not apply. For the present purposes,
however, I will focus on the possible discovery of ETI for which contact'
would be a reasonable hypothesis. Secondly, as Stephen Jay Gould has
argued, even if life is prolific in our galaxy we should expect radical
diversities in its morphologies reflecting differing evolutionary histories
and contingencies. Still if we focus on what we take to be the essential
characteristics of human cognition, such as the capacities for reason,
verbal, formal, symbolic and abstract language, imagination, art, religion,
ritual, ethics, etc., and if we assume that contact will be established
using technologies both our species and theirs can understand, then we may
be able to formulate some preliminary questions about the implications of
So will ETI be found to be abundant or rare? This is clearly an empirical
question, and attempts at estimating its answer in advance of actual
contact are highly controversial. However, there are some really
interesting philosophical and theological questions which are raised by the
issue of abundance which we can address prior to learning the empirical
answer. Let us focus on one such issue: would the relative abundance of
ETI influence our view that life is inherently significant or essentially
Some scientists have suggested that life itself has little significance
whether or not we are alone in the universe. They see life as essentially
meaningless, a random product of physics and chemistry of no more
significant than the wetness of water or the structure of Saturn's rings.
It's just what matter does when really unusual conditions occur, but the
universe, at rock-bottom, is just endless mass-energy and curving
spacetime. Such cosmic pessimism' of cosmic dysteleology' is of course
a philosophical interpretation of the scientific question of abundancy not
forced on us by the scientific facts, but it is one that has been widely
propounded by immanent scientists such as Bertrand Russelll and Jacques
Monod. It is certainly the impression theoretical physicist and Nobel
laureate Steven Weinberg gave in his often-quoted conclusion to his 1979
book on Big Bang cosmology, The First Three Minutes: "It is almost
irresistible for humans to believe that we have some special relation to
the universe, that human life is not just a more-or-less farcical outcome
of a chain of accidents reaching back to the first three minutes, but that
we were somehow built in from the beginning...It is very hard to realize
that (life on Earth) is just a tiny part of an overwhelmingly hostile
universe...The more the universe seems comprehensible, the more it also
I disagree with this view. Instead, I think the very fact of life, even
if it has only evolved on our planet, is a key to the universe itself.
Physicist Freeman Dyson puts this alternative nicely in Disturbing the
Universe. He writes: "The laws (of subatomic physics) leave a place for
mind in the description of every molecule...I do not feel like an alien in
this universe. The more I examine the universe and study the details of
its architecture, the more evidence I find that the universe in some sense
must have known that we were coming." And in his 1985 Gifford Lectures,
Infinite in All Directions, Dyson presses the point more forcefully. He
explicitly rejects Weinberg's opinion, telling us instead he sees "...a
universe growing without limit in richness and complexity, a universe of
life surviving forever and making itself known to its neighbors across the
unimaginable gulfs of space and time...Twentieth-century science provides a
solid foundation for a philosophy of hope."
I agree with Dyson's philosophical argument, and I want to move the claim
forward another step by introducing a theological perspective here. Even
if life was extremely rare in the universe --- in fact, even if it only had
occurred on Earth --- I believe it is a clue to the theological meaning of
the universe as a whole. Let me illustrate this in the following way:
Suppose you are lost and thirsty in a vast, dry desert. Suddenly you spot
a palm tree on the horizon. Are you going to say, "well since the desert
is so vast and barren, that wavy tree is insignificant, a statistical fluke
not worth taking seriously"? Hardly. Instead its very scarcity makes it a
tremendous discovery, for a hidden spring of life-giving water lies at its
roots, shaded beneath its swaying branches. I feel this way about Earth
and about those planets we may one day discover to harbor life. Our
planet, this blue-green watery jewel, is like the palm tree in what might
in fact be a vast interstellar desert. Here the spirit of the living God,
working patiently in, through, and within the processes of biological
evolution over countless ages, has produced what is, arguably, the most
remarkable construction in the galaxy: the primate central nervous system.
The number of connections between the neurons of the human brain is greater
than the number of stars in the Milky Way. This staggering complexity makes
possible --- and we still are not really sure how --- the almost
unimaginable feat of self-consciousness, of knowing oneself as a free,
moral agent in the world. On our planet, at least, we are privileged to
discover a hint of what God's intentions might have been in creating a
universe like ours, with its particular laws of physics. For when the
evolutionary conditions are right as they have been on Earth, and as they
may be elsewhere in our galaxy, God, the continuous, immanent, ongoing
creator of all that is, working with and through nature, creates a species
with the capacities for reason, language, imagination, tool-making, social
organization, and self-conscious moral choice, can enter into covenant with
God, the ultimate source of life. Thus, if it takes a thousand million
stars to produce the conditions for the possibility of a sea urchin, if it
takes a billion years of tinkering with genetic dice to produce a
hummingbird, and if it takes a million years of scratching on bark and
vocalizing intentions to produce a child who can reach out through human
artifacts and chalkboard calculations and touch the edge of the visible
universe, then the universe itself points back to our planet as signaling
its true meaning. Life then is surely the pearl of great price.
Theologically, then, it is not really a question of statistical odds
which make life special, but what life inherently involves wherever it has
evolved. The significance of life lies in the way each stage of life
internalizes the whole history of life's immense journey, the way genes,
organs, limbs, and so on gather together, recapitulate and give an emerging
meaning to all of the past conditions of the planet which together have
made life possible. And it is the way life allows those eons of evolution
to take the elements of matter, the stardust of the billion year old past,
and bring it to consciousness of itself as a self who knows itself and
discovers this journey. If it took the precise characteristics of this
universe to allow for the possibility of the evolution of life, even if
only on Earth, then it is life as such that gives significance to our
universe, even if ours is only one of a countless series of universes as
some inflationary and quantum cosmologies depict. Put theologically, I see
life as the enfleshing of God's intentions, biological evolution as the
ongoing expression of God's purposes in creating all that is, and creatures
with rationality and moral conscience as being, at least in one sense, in
the imago dei, the image of God, for it is life like this which offers to
nature nature's conscious experience of the God who act within nature.
Topics 2) and 3) may best be treated together. Thus: 2) Will intelligent
life be capable not only of rationality but also, and inevitably, of moral
judgment? And, if so, 3) will evolutionary biology determine its moral
content or will it merely bequeath intelligent life with moral capacity,
leaving moral content to be determined independently of biology?
We turn here to the question of the biological origins of ethics. This is
not an attempt to derive ethics from biology, a move which is usually seen
as falling prey of the naturalistic fallacy.' Rather it is an attempt to
argue that our human experience of moral capacity, like our capacity for
rational thought, is rooted in our biological nature and bequeathed us by
evolution. If such an argument holds, it might suggest that wherever
evolution results in creatures capable of rational intelligence they would
also be equipped with moral intelligence. A further question, but
intimately related to this, is this: if moral capacity arises in tandem
with rationality, will not only the capacity but also its contents be the
same as ours? In other words, if evolution necessarily bequeaths moral
capacity to intelligent life, will it also determine the actual values,
beliefs, ethical principles that such life holds dear?
These questions can be addressed from both scientific, philosophical and
theological perspectives. Sociobiologists and, more recently, behavior
geneticists, have explored the biological basis of human social behavior in
order to determine the relation between evolutionary and genetic constraint
and cultural expression. Many of them, notably E. O. Wilson and Richard
Dawkins, are unabashedly reductionistic, interpreting their scientific
research in deterministic and functional accounts of human behavior.
Michael Ruse has argued extensively that both the capacity and the content
of human morality are entirely the products of evolution. In a recent
article, Ruse begins by distinguishing between biological altruism as any
cooperative behavior between organisms that increases evolutionary gain',
and moral altruism involving conscious choices we make to help others
because it is right' to do so. For Ruse, moral altruism is a realization
of nonmoral, biological altruism; thus he interprets morality in terms of
biology, but he takes the argument a crucial step further. Moral altruism
"... has no objective foundation. It is just an illusion, fobbed off on us
to promote altruism'". Though sharply critical of Ruse, Holmes Rolston
helpfully summarizes Ruse's position for us: "Ethics is not true, though it
is functional. Paradoxically, though, ethics cannot be functional unless
it is believed to be true in an objective sense, a false belief."
Geneticist Francisco J. Ayala takes a very different position on these
issues. For nearly three decades he has argued against reductionism in
biology; he disagrees dramatically with Ruse over the evolutionary origins
of human moral capacity. According to Ayala, evolution selected for
intelligence in our ancestral hominid line and ethics is one of its many
byproducts. "Ethical behavior came about in evolution not because it is
adaptive in itself, but as a necessary consequence of man's (sic) eminent
intellectual abilities, which are an attribute directly promoted by natural
selection." So, while ethical capacity is adaptive, its content is open to
being determined by cultural processes, including philosophical and
religious considerations. Furthermore, free will can empower us to act
against natural predispositions, such as selfishness, if they are judged
morally unacceptable. Conversely, some moral norms, such as justice and
benevolence, may be inconsistent with behaviors favored by natural
selection. In addition, moral norms differ between cultures and evolve
over time. Thus for Ayala the axiological role played by culture is one of
the principle factors which differentiates humanity from its evolutionary
origins. Similar arguments against reductionism have been developed by a
wide range of scientists and philosophers, including Theodosius Dobzhansky,
Ernst Mayr, Arthur Peacocke, Ian Barbour, Nancey Murphy and George Ellis.
Turning specifically to the theological issues here, the approach adopted
by most Christian scholars today in theology and science is that God is the
ongoing creator of the universe, acting through the processes of
evolutionary and molecular biology to bring about life and, at least on
earth, creatures capable of reason and moral judgment. What science
discovers and describes in terms of the laws of physics and biology is the
immanent action of God creating in, through, under and with the underlying
regularities of these natural processes. Even if a fully reductionist
account was warranted for the biological origins of human moral behavior,
theologians could argue that this describes, and does not undercut, the
processes through which the good, the true, the virtuous are revealed to
us. In an emergent, non-reductionist account, though, there are much more
ample grounds for understanding the complex interaction between genuinely
new levels of human moral insight and our creaturely, evolved embedding in
the sweep of life on earth.
It would seem, then, that whether or not the reductionist approach to the
evolution of moral capacity is defended, there are serious scientific
reasons to expect that the emergence of both rational and moral capacities
will be found wherever life has evolved to the point of intelligence in the
universe. Theologically I would find such a result, if it were true, as a
wondrous exemplification of the intentions of God in creating a universe
like ours, namely that creatures capable of genuine community and covenant
can arise and enter into life together and with God.
More specifically, what sorts of responses might Christian theologians
offer to the discovery of ETI with rational and moral capacities?
Physicist Paul Davies has repeatedly predicted that it would "(shatter)
completely the traditional perspective on God's relationship with man
(sic)." But theologian Ted Peters finds "little or no credible evidence"
for Davies' view, though he recognizes that what he terms "exo-theology"
has seldom been explored to the depths it deserves. Indeed there is rich
evidence in the history of ancient Greek and medieval and early modern
Christian thought supporting a "plurality of worlds" and even
extraterrestrial life in the universe. Again, although it has not been
widely and systematically considered, contemporary theologians have been
genuinely open to the possibility of rational and moral ETI. As examples,
Ted Peters cites Roman Catholics, such as George van Noort, Theodore
Hesburgh, Hans Küng, Karl Rahner, and Francis J. Connett, conservatives
such as Billy Graham, and mainline Protestants such as Krister Stendahl, A.
Durwood Foster, and Paul Tillich.
But what of moral failure, our final issue? Will it too be universe, as
it is on earth? With this we turn to the fourth and final topic for this
brief paper: 4) If moral agency evolves elsewhere in the universe, will
it inevitably exhibit moral failure, or is our generic human experience of
moral failure strictly the result of our particular evolution, leaving us
to expect there to be other civilizations that are entirely benign?
This question embodies a painful and tragic reality at the heart of human
existence. Why do we act with a level of violence against our own kind and
other species which far exceeds the needs of survival and the level of
violence of all other forms of life on Earth? Why do we lust after power
and indulge in travesties like racism, sexism and specism? Put
theologically, why do we sin? Why do we fail to love and serve God and one
another, and indeed all of God's creation, and instead indulge ourselves in
unbridled pride and inordinate sensuality? The Christian tradition has
sought to respond to this foundational question by asserting that what
seems paradoxical: sin is not an intrinsic part of human nature, yet we all
sin inevitably. Making it intrinsic would rob us of our individual and
corporate responsibility; failing to recognize its inevitability would lead
to the false hope that we can free ourselves of it without depending on the
grace of God. Each of us inherits both the imago dei, the image of God',
and the inevitability of sin, yet as a species, both are de nuovo. This
traditional response can be refracted and restructured creatively within
the context of biological evolution, particularly with the theme of
novelty within continuity' which many scholars see as the key
characteristic of evolution. Thus we as a species inherit diverse
propensities from our pre-hominid past, but in homo sapiens something
strikingly new emerges. This newness' is manifest both in our capacity
for abstract thought, formal language, complex technologies, art and
science, and our ruthless violence and our insatiable appetites for power
and control. It is only through the grace of a loving God that our lives
can be transformed into the fullness of what it truly means to be human.
Another way to express this claim is that the formation of authentic human
virtue --- authentic personhood --- requires a lifetime of genuine
wrestling with tough moral choices and, even more painfully, the confession
and repentance of actual moral failure.
What then about ETI? I have suggested for scientific, philosophical and
theological reasons, the essential characteristics of human life is a
genuine clue to the nature of life in the universe and not just a terrible
moral or evolutionary fluke of the evolutionary processes on Earth. For
this reason I believe ETI will experience much the same kind of moral
dilemma that characterized human experience. I also believe that ETI will
experience an empowering for that struggle by a source which transcends its
natural capacities. Put into theological language, I believe --- perhaps I
can even say that I predict! --- that the God will be present and active
to the struggles of life throughout the galaxy, and that God's grace will
redeem and sanctify every species in which reason and moral conscience are
kindled. As a Christian theologian and scientist, I would want to think
this through in terms of a key question: should Christians expect that a
single Incarnation of Christ in Jesus is sufficient for the redemption of
all life in the universe, or should we expect there to be multiple
Incarnations of Christ in each species of ETI? Interestingly, modest
support for both options can be found among both Protestants and Roman
Catholics: a single, universally efficacious Incarnation is suggested by
Protestants Ted Peters and Wolfhart Pannenberg and Roman Catholics L. C.
McHugh and J. Edgar Bruns, while multiple Incarnations have been considered
by Protestants Paul Tillich and Lewis Ford and the Roman Catholics Karl
Rahner, E. L. Mascall and Ernan McMullin. All agree, however, that
wherever ETI exists, it will be the creation of a loving and redeeming God.
Clearly the empowerment by God of the full flowering of authentic
personhood is at the heart of the Biblical witness. Taking this to entail
such flowering throughout the diverse species of ETI throughout the
universe leads to a profound reformulating and creative transformation of
Christian thought and action, whose consequences would affect our ongoing
search for deeper religious pluralism and a fuller understanding of the
relation between humanity and the plenum of species in our terrestrial
environment. Thus, regardless of what lies ahead as we await first
contact' with ETI, pursuing these kinds of questions and reflections will
be immensely valuable.
Implications of possible biological evolution outside habitable zones in solar systems
(Working Draft Only)
The Abdus Salam International Centre for Theoretical Physics (ICTP)
P.O.Box 586; Strada Costiera 11; 34136 Trieste, Italy and
Instituto de Estudios Avanzados Caracas 1015A, Venezuela.
Abstract: We discuss the interface between astrochemical to astrobiological studies. In particular, we concentrate on the discussion of a conjectured universal evolutionary pathway to eukaryogenesis, multicellularity, neurogenesis and intelligence. We restrict the consequences of the conjecture to two aspects: its possible implications in biological evolution outside habitable zones in solar systems and the likelyhood of the onset of other intelligence; secondly, we discuss the implications in the cultural area. Our conjectured evolutionary pathway offers the basis of a theory in terms of which, on the one hand, we can introduce rationalisation in the planning of experiments that are worthwhile and feasible in the forthcoming campaign of Europa missions; on the other hand, it also gives us an opportunity for rationalising the dialogue that should be maintained with philosophers and theologians with respect to the incorporation into our cultural background of a new view of our position in the universe.
The only intelligent life that we know about in the universe
is life on our own planet. We have no idea of how representative
it might be of life elsewhere, although it is conjectured that,
given suitable environmental conditions, if life started somewhere
else it would be constrained to take an evolutionary pathway to
eukaryogenesis and multicellularity (Chela-Flores 1998a, 1999;
Seckbach et al., 1998, Seckbach et al., 2000). Beyond that preliminary
stage in our approach to astrobiology, we shall now argue that
terrestrial biota teaches us that multicellularity is inexorably
linked with neurogenesis, which, in turn, is linked to the process
of synaptogenesis and finally to the formation of cerebral ganglions
at the lowest levels of a given tree of life. In fact, it has
been argued in the past that the emergence of eukaryotes may have
been a highly likely consequence of the coupling of the complementary
metabolisms of two or more prokaryotes (Schwartzman, 1999). Sagan
suggested that eukaryogenesis should be included in the Drake
equation (1973); this point has been developed recently (Chela-Flores,
2000a). The question whether nature in an extraterrestrial context
steers a predictable course is clearly still an open question,
but some hints from the basic laws of terrestrial biology: natural
selection and the existence of a common ancestor (a 'cenancestor')
for all the Earth biota (Becerra et al., 2000) can be interpreted
as evidence in favour of the fact that to a large extent evolution
at a cosmic level is predictable and not contingent. The underlying
question concerns the relative roles of adaptation, chance and
history, a topic which is subject to experimental test. Indeed,
some experiments using bacterial populations propagated in identical
environments, achieved similar fitness independent of prior history
or subsequent chance events (Travisano et al., 1995).
Further support from independent teams suggests that natural selection overrides the randomness of genetic drift; in other words, natural selection seems to be powerful enough to shape terrestrial organisms to similar ends, independent of historical contingency (Rundle et al., 2000). On the other hand, some arguments militate in favor of a human-level of intelligence being reached by the conjectured universal constrained evolutionary pathway towards eukaryogenesis, multicellularity, neurogenesis, synaptogenesis and intelligence. Certainly, in an extraterrestrial environment the evolutionary steps that led to human beings would probably never repeat themselves; but that is hardly the relevant point: the role of contingency in evolution has little bearing on the emergence of a particular biological property (Conway-Morris 1998a).
2. Evolutionary convergence
The inevitability of the emergence of particular biological
properties is a phenomenon that has been recognized by students
of evolution for a long time. It is referred to as 'evolutionary
convergence'. This may be illustrated with examples taken from
malacology and ornithology (Chela-Flores, 1999):
· In the phylum Mollusca the shells of both the camaenid snail from the Philippines, or a helminthoglyptid snail from Central America, resemble the members of European helcid snails. These distant species (they are grouped in different Families), in spite of having quite different internal anatomies, have grown to resemble each other outwardly over generations of response to their environment. In spite of considerable anatomical diversity, mollusks from these distant families have tended to resemble in a particular biological property, namely, their external calcareous shell.
· A second example is provided by swallows (Passeriformes) a group which is often confused with swifts (Apodiformes), but are not related to them (Austin, 1961). In fact, the taxons to which these birds belongre orders, rather than families. Members of these two orders differ widely in anatomy and their similarities are the result of convergent evolution on different stocks that have become adapted to the same ways of living in ecosystems that are similar for both species.
In the light of these examples the question of whether our intelligence is unrepeatable goes beyond biology and the geological factors mentioned in the metaphor on the repetition of the history of evolution (Gould, 1991). Indeed, the question is rather one in the domain of the space sciences in which radio astronomers have led the way with the SETI project (Drake and Sobel, 1992). Not only will similar biologic features be achieved by means of evolutionary convergence, but one of the most remrkable biological attributes of life on Earth is known to have followed a perfectly treaceable pathway in multicellutar animals, namely the the acquisition of functional brains.
3. The origin of the first neuron and protobrain on Earth
There is strong selective advantage for multicellularity of
eukaryotic cells that have already become neurons; such an event
occurred very early during multicellular evolution on Earth, as
described in detail in the Villegas-Castillo-Villegas collaboration
(Villegas et al., 2000): Single-celled Eukarya organisms such
as the ciliated protozoan Paramecium, have to deal with problems
of survival just the same as higher animals.
This in turn implies that they must have receptors for sensing the environment, a signal integration mechanism for responding to external stimuli. Further examples, such as bacteria and archaeans exhibit similar behaviour. Indeed, in Paramecium, mechanosensitive calcium channels as well as voltage-gated calcium and potassium channels in the cell membrane and in charge of the cilia movements, are the essential components of the mechanism for sensing, integrating and responding to the stimuli. This and the associated successive steps, share basic characteristics with the functioning of a hypothetical simple neuron. Sponges, the most ancient metazoans present a higher degree of organization than the protozoans, being the multicellularity one of their important features. This multicellularity allows the sponges to increase in size and also to have a high degree of coordination, specially aimed to maintain their main activity, which is pumping and filtering sea water to obtain food. Physical and chemical stimuli elicit these activities. All-or-none propagated electrical impulses have been recorded in the sponge Rhabdocalyptus dawsoni in response to electrical shocks. However, the electrical signaling system of this species appears to be similar to other non-nervous pathways carrying action potentials in other organisms. In addition, the presence of a nervous system has not been demonstrated.
The next group corresponds to Coelenterates, comprising Cnidaria and Ctenophora, in which the first neurons and true nervous system exists. It is constituted by individual interconnected neurons transmitting, chemically or electrically, in both directions and forming a sort of nerve net. Untrastructural studies have revealed neurons bearing neurosecretory dense granules and with isopolar processes termed neurites connected by synaptic-like junctions. The important related process of synaptogenesis (on the pathway form neurons to cerebral ganglions) also occurred early in the evolution of multicellularity on Earth biota, and has been reviewed recently (Palacios, 2000).
Low-threshold calcium-dependent channels and high-threshold sodium-dependent channels have been described in R. dawsonii. In addition, three distinct potassium channels, according to their inactivation kinetics (fast, intermediate, or slow) have also been detected. Some neuromuscular synapses as well as interneuronal synapses reveal peptides which were amongst the first neurotransmitters appearing in evolution.
The flatworms, Platyhelminthes, that evolved after the Coelenterates, together with the Nematodes have a nervous system resembling a hybrid between the coelenterates nerve net and the centralized nervous system of higher animals. They have a cerebral ganglion that represents a central nervous system with many types of neurons, including vertebrate-like multipolar neurons, and neuroglial cells. The neurons have sodium channels and the major types of potassium channels. Some of these channels have been already cloned and sequenced. In addition, an advanced degree of synaptic plasticity is suggested by selective excitation and inhibition of the neuronal pathways. Several neurotransmiters have been found in both groups of animals, including neuropeptides.
It should be stressed that in evolution neuronal behaviour arose as soon as the conditions on Earth were ready to allow the transition form single-celled dominated biota to multicellular organisms. Due to its selective advantage it seems inevitable that eukaryogenesis is followed by neurogenesis, synaptogenesis and, finally, to cerebral ganglions (and hence nervous systems and brains, intelligence and civilizations)
The above arguments strongly advocate in favor of the existence
of other human-level of intelligence elsewhere in the cosmos.
Essentially the argument hinges on whether the basic transition
form prokaryotes to eukaryotes has taken place.
We consider that not only physico-chemical processes regulate the structure and evolution of the universe; but besides all laws of nature are of general validity, irrespective of the location of the observer in a given galaxy. In particular, this "strong" principle of universality of the natural sciences forces upon us the consideration that the natural laws of biology, as known to us on Earth, also apply elsewhere.
We have learnt form astrochemistry that the occurrence of carbon atoms and molecules is ubiquitious in extreme regions of circumstellar zones, in the interstellar medium, not forgetting a multitude of planets orbiting around many planet-beraring stars (Sofia, 2000); we interpret these facts (Sec. 4) in terms of a model of the universe, in which it is increasingly unlikely that our solar system is a unique cosmic environment. We have also learnt that chemical complexity is inexorable due to solids, such as dust grains, satellites, comets and other small objects of solar systems (Greenberg et al., 1993). Such chemical complexity was the trigger to prebiotic evolution; this led in a short geologic interval to biologic complexity.
Hence the evolution of biological complexity in our particular cosmic environment is constrained by the above-mentioned two laws of biology first suggested by Charles Darwin. What we wish to discuss in the present work is the experimentally testable consequences, such as eukaryogenesis, which has been assumed to be an inexorable consequence of the natural laws in the pathway to protobrains and, eventually, to brains capable of allowing their bearers to develop civilizations and interstellar communication. We postpone the discussion of positive results of tests of extraterrestrial eukaryogenesis to Secs. 6 and 7.
4. Europa as a case study of the satellites of Jupiter-like planets
4.1. a radiation-based ecosystem of microorganisms?
We follow the discussion (Chyba, 2000), according to which
the evidence gathered throughout the Galileo mission suggests
that the chemistry of the ices of water and carbon dioxide that
cover the Jovian moon Europa might support a radiation-based ecosystem
of microorganisms. It is conceivable therefore that independent
of whether there are hydrothermal sources at the bottom of the
ice-covered ocean, a thriving community might have evolved in
The relevance of the various sources for living organisms in a satellite of a Jupiter-like planet such as Europa cannot be overemphasised namely: radiation-dominated or the deep volcanic vents:
For if the dynamics of the formation and evolution of our own solar-system are not unique cosmic phenomena, then water (such as the abundant supply in Europa) will be delivered to (mainly) silicate bodies by means of collisions with comets. The evidence for such a mechanism is persuasive and has been reviewd recently (Campins, 2000). Since the presence of liquid water is a strong factor for the emergence of life, then these arguments gives rise to the problem of how to select appropriate experiments to be tested in situ, once surface landers are able to filter meltwater from Europa's ice.
Implications of possible biological evolution
4.2. towards distinguishing europan microorganisms
One way of approaching the intricate problem of testing the
degree of evolution of possible Europan microorganisms is to consider
the analogous problem with the DNA that makes up the chromosomes,
namely, the folding of the 100-Å nucleosome filament.
There is a hierarchy of levels of folding beyond the 100-Å
nucleosome filament: The next level of complexity is provided
by 300-Å filament, which is arranged into a solenoid-like
configuration with about six nucleosomes per turn (Fitch and Klug,
1976). During interphase in the cell cycle, it is this solenoid-like
arrangement that constitutes the most abundant form of chromatin.
However, at later stages in the cell cycle this structure serves as the basis for further folding, ending up at the highest degree of folding observed at the metaphase chromosome. This is an extremely fortunate feature from the experimental point of view. We only need to recall that the ultimate aim of the Europan biology experiment is to develop robotic tests that are compatible with the reduced dimension. of a Europa lander. Indeed, chromosomes stain easily, in a well-defined manner.
The biochemical basis for the difference between heterochromatin (the more compact structure of chromatin) and euchromatin (its less compact form), remains unknown. In both cases the 100-Å nucleosome filament contains approximately the same DNA/histone ratio (Watson et al., 1987a). Heterochromatin is not only a clear hallmark of eukaryogenesis, but that heterochromatin is also a unique indicator of eukaryoticity, which is amenable to the tasks that a surface lander might carry out with the meltwater on the surface of Europa.
4.3. ON THE IDENTIFICATION OF A EUROPAN EUKARYOTE IN SITU
Many difficulties are inherent in the eventual design of an assay that would intend to identify eukaryotes, robotically, in an extraterrestrial environment. This question begins to be important in view of the decisions that have to be made in selecting which biological experiments should be performed in Europa, for instance, by means of the surface lander. Some examples may serve to illustrate the underlying difficulties:
· Confusion with prokaryotes that may have developed an internal membrane. Occurrence of an internal membrane-bounded cell compartment wholly containing the genomic nucleic acid is no guarantee that the cell in question is a eukaryote. In fact, this may be illustrated with two differnt genera of the bacteriun planctomycetes: Pirellula and Gemmata (Lindsay et al., 1997).
· Silicification experiments. Laboratory fossilisation of micro-organisms has led to the identification of one artefact, which can cause confusion in the identification of micro-organisms. It has been observed that an artificial nucleus formed during the process of fossilisation (Westall et al., 1995). If such a phenomenon is preserved in the natural fossil record, then it can lead to a confusion with the eukaryotes.
For these reasons, we confine our attention to the clearest
hallmark for eukaryogenesis: heterochromatic genomes that respond
in an unambiguous manner to well-defined dyes, the result of which
could be recorded with video equipment for later analysis, after
relaying the results to an Earth-bound laboratory.
4.4. Techniquesfor staining the genome
Quinacrine fluorescent dye inserts itself between base pairs
in the DNA helix producing the so-called Q-bands, which for an
eventual mission on a lander would probably suffice. Adjacent
areas stain differently. The bands give a clear indication of
slightly different modes of DNA packaging. It is the tightness
of the genomic material that would be an indicator of a higher
degree of evolution (Chela-Flores, 1998b).
The question is not so much what is the chemical detail of the genome, but what is the degree to which it has been packaged. It may be argued that gene activity is correlated with light-staining bands. (For instance, genes that are transcriptionally active are light-staining (Watson et al., 1987b) This aspect of the proposed experiment is its most important feature, since it does not force upon us the requirement of previous detailed knowledge of the putative Europan biochemistry. The main scope of the experiment is to expose eukaryoticity at the level of gene expression, whose most characteristic indicator is heterochromaticity (i.e., a tightly packed genome).
5. Bridging a gap in astrobiology
Our thinking is based on the exclusion of refuges against evolution
(Little et al., 1997). This new insight is based on the remarks
that the modern vent environment is not a refuge for the known
Paleozoic and Mesozoic shelly vent taxa and on the fact that there
has been movement of taxonomic groups in and out of the vent ecosystem
throughout time (Little et al., 1998).
In other words, this remark rules out the possibility that these deep-sea environments are refuges against evolutionary pressures. In other words, the evidence so far does not support the idea that there might be environments, where ecosystems might escape biological evolution, not even at the very bottom of deep oceans. It is then reasonable to assume that any micro-organism, in whatever environment on Earth, or elsewhere, would be inexorably subject to evolutionary pressures. On this planet the eukaryotic cellular blueprint seems to have been the consequence of over 2 Gyr of evolutionary pressures acting on the prokaryotic blueprint. The first appearance in the fossil record of eukaryotes occurred during the Proterozoic Eon, after prokaryotic communities (stromatolites) were well established in the Archean Eon (Schopf, 1993).
It still remains to be confirmed, or rejected, whether the Europan environment may have had liquid water over geologic time. In such a favourable environment a primordial archaea community would have had sufficient time for evolutionary pressures have modelled a primordial archaea community. If these conditions occurred on Europa, then, according to our conjecture (cf., Sec. 1), eukaryogenesis would have been inevitable. The most recent observational evidence remarkably suggests the presence of an ocean (Carr et al., 1998).
In the present work we have defended the thesis that if biological experiments testing for evolutionary trends (cf., Sec. 4) were to be successful, they would bridge the remaining gap in astrobiology. In other words, the conjecture (cf., Sec. 1) would serve as a firm scientific basis on which to develop eventually the science of the distribution of life in the universe.
6. Implications of other life on culture
From what we have said above, we are induced to face the question
of the prevalence of the living state throughout the cosmos. This,
in turn, leads to the question of how to accommodate this radically
new situation in a general cultural context. We conclude this
work with some brief comments.
Science and religion are both concerned with the common understanding of the origin of life in the universe. Since they largely address the same questions, both of these aspects of human culture should at some point converge. With subsequent progress in the main three cultural domains (science, philosophy and theology), convergence is therefore unavoidable. There does not seem to be any evident convergence at present, but the status of the present relationship between the three disciplines: science, philosophy and theology (relevant to an eventual integrated view of the appearance of intelligent life on Earth) has recently been comprehensively discussed (John Paul II, 1992): Contemporary culture demands a constant effort of synthesis of knowledge and of an integration of our understanding... but if the specialisation is not balanced by an effort aiming to pay attention to relationships in our understanding, there is a great risk of arriving at a "splintered culture", which would in fact be the negation of the true culture.
We may avoid a splintered culture by bringing closer to each other various approaches regarding the origin, evolution and distribution of life in the universe. This is an area of research in which we should expect substantial progress to occur in the future. This is particularly likely, due to the large funds potentially available for space missions. Moreover, we are bound to converge towards better answers, due to the deep insights that all of us, scientists, philosophers and natural theologians can collectively provide in the future.
The present time is one of expansion of the number of people that are interested in the problem of the origin of life. Theologians have been deterred to get involved in this fascinating field, mainly due to some reservations that can be traced back a long time to the fundamental question of how to read the Holy Books of the three monotheistic religions of the world, namely the Old Testament of the Holy Bible which is shared by Judaism, Christianity and Islam.
In the Book of Genesis there are questions raised that are of interest to theologians, philosophers, scientists and artists. To extend the fortunate phrase of Lord Snow, we may refer to these four groups as the 'four cultures'(Snow, 1978). In this terminology, it is hardly surprising that the fourth culture (art) should have shown interest in Genesis. The very rich iconography of Christianity and Judaism was a permanent source of funding for artists throughout the rise of Western civilisation (Clark, 1969). The reason why the third culture (science) has been interested in the evolution of life is self-evident. Science took one of its most transcendental steps towards understanding the complexity of the biosphere when Darwin formulated natural selection as a mechanism for evolution.
Progress since the publication of the Origin of Species (Darwin, 1859) has been considerable. The second culture, philosophy, has been intricately connected with the development of Darwinism. Philosophers such as Karl Popper have meditated deeply on the philosophical implications of the Theory of Evolution.
We wish to dwell at a certain length on the interest that
the first culture, theology, has had on the question of the origin
and evolution of life on Earth and the possibility of there being
life elsewhere in the universe. Traditionally there has been a
certain caution of theologians with respect to the questions that
we have discussed at some length in this work. Saint Augustin
touched on this question in The City of God with respect to
possible conflicts that may arise from a literal reading of the
Bible (St. Augustin, 1984). In our own time a clear position
was expressed at the Pontifical Academy of Sciences, which had
met to discuss the origin and evolution of life.
In this message, the subject of the present book was defined as (John Paul II, 1996): "a basic theme which greatly interests the Church, as revelation contains, for its part, teachings concerning the nature and origins of man".
Raising the Augustinian conundrum of whether scientifically-reached conclusions, and those contained in revelation on the origin of life, seem in contradiction with each other:
"In what direction should we seek their solution? We know in effect that truth cannot contradict truth".
This position has opened the way to a fruitful dialogue between scientists and theologians, two cultures, which are not too distant from each other (Polkinhorne, 1996). New understanding is arising between cultures that were once distant from each other. Such progress can only open the way to enhancing the subject of the origin, evolution and distribution of life in the universe, a field of research that is bound to continue its robust growth.
7. Discussion: What is the position of Man in the universe?
However, in spite of these persuasive arguments from the life
sciences discussed up to this point, some astronomers and paleontologists,
independent of the evidence from biology, still defend the opposite
point of view (Brownlee and Ward 2000). This position has been
recurring periodically, and in analogy with earlier restricted
views of man's position in the universe may be referred to as
the biogeocentric point of view.
By biogeocentricism we mean the belief that life has occurred only on Earth, which has been advocated in the past (Mayr, 1995; Monod, 1972). Some have gone as far as assigning extraterrestrial life an "improbability of astronomical dimensions", while others felt that:
"The present structure of the biosphere certainly does not exclude the possibility that the decisive event occurred only once".
More recently, the biogeocentric position has been maintained (Conway Morris, 1998b):
"If indeed we are alone and unique, and this possibility, however implausible, cannot yet be refuted, then we have special responsibilities."
Almost a century and a half separate us from the concern expressed by Sir Charles Lyell regarding the position of Man amongst all living organisms. It seems that the underlying difficulty barring convergence is still related to inserting Lyell's "ugly facts" of Darwinian evolution into our culture. Darwin was prudent enough to avoid ideological issues. He even avoided philosophical issues. These were inevitably raised subsequently by Russell in Religion and Science (Russell 1997):
From evolution, so far as our present knowledge shows, no ultimately
optimistic philosophy can be validly inferred.
Darwin concentrated on the narrow, but transcendental problem of establishing the theory of evolution of life on Earth and prudently postponed wider issue of the position of Man in the universe. At the beginning of a new era in space research (Burrows, 1998), a much wider problem remains to be solved, namely we still do not know what is the position of our tree of life in what we may call the "Forest of Life". However, we may still have to wait for preliminary progress in the still undeveloped science of the distribution of life in the universe. One of the main difficulties is deciding the position of Man in our parochial tree of life. General consensus on this issue has been missing since Lyell's time. We hope to have conveyed to the reader the multiple hints from science that such discoveries are likely to take place sometime in the future. The implications are likely to have an impact in our culture requiring adjustments possibly more radical than those arising form the evidence that humans descend from microorganisms (Jastrow, 1997).
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