Against a wide cultural background we discuss our current view of the search for other intelligence in the universe. This question is of common interest amongst others to theologians, philosophers and scientists. We summarise possible environments where the pathway towards intelligent life could initiate. We discuss some implications of the ascent of microbial life towards intelligent beings. We restrict our discussion to the search for the first steps towards intelligence in our own solar system. More specifically, we confine our attention to the outer solar system. Besides the most evident case of Mars, possible environments are: the pair of galilean satellites of Jupiter: Europa and Ganymede. Another interesting possibility is the Saturnian iced moon, Enceladus. As a consequence of new knowledge in astrobiology, we discuss some philosophical and theological questions that may arise from the eventual discovery of extraterrestrial life.
(*) International Symposium "Origin of intelligent life in the universe: Evolution, distribution and originality". Villa Monastero, Varenna, Italy. 28 September till 1 October 1998.
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The study of the implications of the search for extraterrestrial life would be a less difficult task if our culture were better integrated. Unfortunately, we are still far from having a unified culture. It has been mentioned in the past that culture runs the risk of being "splintered" , if specialisation is not balanced by an effort to pay attention to relationships between different cultural aspects of our understanding of nature.
In the first Varenna Symposium we attempted to insert the origin of life in the context of the origin of the universe itself . We attempted to demonstrate some relationships between the origin of life and other aspects of culture, namely, theology, philosophy and art. Although we are still not anywhere near unifying all learning, such Ionian enchantment  is for some still desirable. Indeed, this objective was pursued in ancient times by the Greek philosophers in Ionia.
In the early 20th century Ionian enchantment was the driving force of a small group in the Vienna Circle of Logical Positivists. This group included scientists and philosophers that met regularly in Vienna and Berlin. Independent of the shortcomings of the Viennese Positivists , discussing a given problem in a wider framework than that of a specialised topic, has today a practical advantage for us: This wider framework will allow access to a richer array of metaphors, examples and analogies. This, in turn, will facilitate our discussion of the all-important problem of the origin, evolution and distribution of life in the universe. For simplicity we shall refer to this study as 'astrobiology'. More specifically, we will focus on a deep question:
Are we alone in the universe and, if not, what is the place of Man in the universe?
We wish to put in evidence changes that the current view of astrobiology brings onto different aspects of culture, namely, literature, art, theology, philosophy and science. We begin our work by recalling how culture itself emerged gradually in a series of steps.
2. THE EVOLUTION OF CULTURE
The earliest records of cultural activity in humans correspond to works of art. The Magdalenian 'culture' left some fine works of primitive art . This group of human beings flourished from about 20,000 to 11,000 years before the present (yr BP). For instance, we can refer to the 20,000 year old paintings on the walls of the cave discovered in December 1994 by Jean-Marie Chauvet in south-eastern France. Indeed, the birth of art in the Magdalenians' caves, is one of the most striking additions to the output of humans that entitle us to refer to the groups that produced these fine works, as cultures, rather than industries, a term which is reserved to the group of humans that produced characteristic tools, rather than works of art.
2.2. Writing and literature
Traditionally the earliest examples of a writing system have been accepted to be those found in the Sumerian settlements of the Fertile Crescent some 5,500 yr BP. Independently writing was introduced in the Nile Valley during the Pre-Dynastic Period. Recent discoveries suggest that the Egyptian system may have anticipated the Sumerian. Besides the great achievements of the Ancient Kingdom, the Sphinx and the pyramids, a remarkable literature was produced on the shores of the Nile, which has been largely translated during the 19th Century. These compositions are narratives, tales, teachings and poetry. An example form the Middle Kingdom (most probably the XII Dynasty, 1991-1976 BC.) is a substantial body of religious literature, including the "Cycle of Songs in Honour of Sesostris III " .
The most ancient statements about monotheism may be traced back to the New Kingdom (1379-1362 BC). Although it is debatable whether the system initiated during the 18th Dynasty may be called monotheism, in "The Hymn to the Aten", close parallels to the verses of Psalm 104, have been pointed out, not only in words, but also in thought and sequence, anticipating this part of the Bible by several centuries . However, theology is a discourse about God, or the science that treats the divine; the earliest such discourses that influenced directly Western Culture may only be traced back to the oral traditions of ancient Israelites, which were incorporated into the main body of the Old Testament. It is in theological arguments that we find the earliest records of discussions of Man's place in the universe, a topic that is relevant to astrobiology. In the ancient texts quoted above we already find early references to the origin of the earth and the origin of life.
Philosophers came next in the evolution of culture. Its origin may be traced back to Greek philosophy, but their interest in the existence of Man may best be illustrated with the preliminary efforts of Rene Descartes (1596-1650), who is usually considered to be the founder of modern philosophy. Decartes is probably the first man of high philosophic capacity whose outlook is profoundly affected by the new physics and astronomy . Decartes' arguments illustrate some points relevant to the present context. He regarded the bodies of men and animals as machines; in particular, he regarded animals as automata, governed entirely by the laws of physics. He assumed that men were intrinsically different from animals in possessing a soul. Decartes attempted to describe how soul and body interacted, not surprisingly without any real success. To arrive at a continuous argument on the origin of Man, science had to await the arrival of Charles Darwin and his contemporaries.
Scientists are relative newcomers to the question of the origin and evolution of life. Darwinism did not address the question of the origin of Man in the universe in the Cartesian dualistic way (body/soul), but restricted itself only to the observable attributes of Man. Since the time of Galileo the scientific approach differs from that of theologians, in the sense that no appeal to revelation is introduced into our discussions. Scientists also differ from philosophers since no exclusive appeal to rational discussion is expected. To sum up, the evolution of culture, first through the first appearance of art, writing and literature, eventually led to those aspects of culture in terms of which reasonable questions on the origin and destiny of Man could be formulated. Theologians are mainly concerned with the metaphysical concepts of "spirit" and "soul", which do not appear in the scientific literature; one could say that these concepts could not appear, since they are not subject to experimental reproducible tests. Instead, the existence of spirit and soul are based on revelation in the traditional teachings of the monotheistic religions.
3. WHAT IS THE POSITION OF IN THE EARTH BIOTA?
3.1. Are the indicators of a special position of humans in the totality of all earthly species?
Some biologists have favoured a different point of view from those radioastronomers that have been searching for extraterrestrial intelligence (SETI) . The reasons behind this dichotomy may be illustrated with a few facts drawn from taxonomy. From the perspective of biology, human beings represent only a single species among four thousand mammals. Yet, this is a small number when compared with the 30 million species that are expected to constitute the whole of the Earth biota. One aspect of this bewildering abundance of species of which humans are only one, has led to the metaphor :
If the history of evolution were to be repeated, such an alternative world would teem with myriad forms of life, but certainly not with humans.
Our main concern is not the origin and evolution of our own species. Our main concern is rather the likelihood that the main attributes of Man would rise again, if the history of evolution starts all over again elsewhere, not in a hypothetical Earth that would be miraculously reconstructed. We are mainly concerned with the repetition of biological evolution in a planet, or satellite, that may have had all the environmental conditions appropriate for life. Such attributes are, for example, a large brain and consciousness. These features of Man evolved from primates over the last 5 to 6 million years. This is in plain contrast with mollusks. Members of this large phylum of invertebrates to which snails, mussels and squids belong, have survived since the Lower Cambrian. Their first appearance occurred 500 million years ago, about 100 times earlier than the first appearance of Man.
3.2. An exact duplication of our species is not needed in order to replicate our intelligence
In an extraterrestrial environment the evolutionary steps that led to human beings would probably never repeat themselves. However, the possibility remains that a human level of intelligence may be favoured when a combined effect of natural selection and cultural evolution are taken together. This is independent of the particular details of the phylogenetic tree that may lead to the intelligent (non human) organism. To put it briefly, the role of contingency in evolution has little bearing on the emergence of a particular biological property . I would like to illustrate the inevitability of the emergence of particular biological properties with an example of convergent evolution, a phenomenon recognised by students of evolution for a long time. In the phylum of mollusks 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. At this stage 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. Indeed, the question is rather one in the domain of the space sciences; in particular, the question of whether we are alone in the cosmos concerns astrometry measurements for the search for extrasolar planets. This activity has led to the current revolutionary view that solar planets are not unique environments that may be conducive to the origin, evolution and distribution of life in the universe . The presence of a dozen planets in the cosmic neighbourhood of the Sun, argues in favour of the ubiquity of life in the universe. It seems plausible that if the right environments exist elsewhere in our own galaxy, some of the biological attributes of Man may have repeated themselves.
3.3. Constraints imposed by theology on our view of life
A separate question concerns the search for microbial life in our own solar system. So we believe it is more appropriate to shift our attention away from 'attempting a full and coherent account of the phenomenon of Man' . Instead, we feel that the progress of molecular biology forces upon us a search for a full and coherent account of the first transcendental transition in cellular evolution, which may be referred to as the phenomenon of the eukaryotic cell . The task is not easy . But let me dwell on clarifying the terminology.
4. DOES THE SEARCH FOR OTHER FORMS OF LIFE LEAD TO CONTRADICTIONS BETWEEN SCIENCE AND REVELATION?
We have already reviewed some arguments that suggest that the problem of the position of Man in the cosmos depends critically on the evolution of microorganisms up to the level in which eukaryogenesis occurred. This forces upon us the position of the eukaryotic cell in the cosmos, as the main focus of our attention . I feel that such a radical break with the past has some implications in our understanding of the origin and destiny of Man. Nevertheless, none of these arguments lie outside the scope of the question raised in the Papal Message to the Pontifical Academy of Science . The Message to the Pontifical Academy is real progress for better understanding between science and theology . In spite of this important step, the acceptance of evolution has not led to a consensus amongst scientists, either on its mechanism, or on its implications. Nevertheless, in spite of this shortcoming, we shall base our subsequent arguments on Darwin's theory of evolution. This leads us to a discussion of some of the implications that such a search might imply for the dialogue between science and philosophy.
5. WHAT IS THE POSITION OF EUKARYOTES IN THE COSMOS?
5.1. Are there other solar system environments favourable for living microorganisms?
In 1610 Galileo discovered the four large moons of Jupiter with his telescope, a revolutionary instrument for his time. Since 1993 we have the Hubble Space Telescope in terrestrial orbit. But in less than a decade our growing insights on the cosmos will continue when, in 2007 the Next Generation Space Telescope will go into orbit. It will be much larger and powerful than Hubble. However, we still are not through with the optical instruments, as they have not been developed to a sufficient degree that to make them capable of detecting extrasolar earth-like planets. However, satellites in the solar system may yield some partial answers.
5.2. The moons of Saturn
Enceladus is an obvious candidate. Its morphology suggests that in the past there must have been geologic activity with melting of ice on its surface, leaving a terrain without craters. Geologic activity triggered by the vicinity of a giant planet is not a unique phenomenon in the outer solar system. The geysers of Triton have already demonstrated this point. Our emphasis on this matter is not idle: We are now convinced that the vicinity of a star is not the only way to generate life. In the deep terrestrial oceans, volcanic activity supports life quite independent of Sun-driven photosynthesis. The universality of the laws of physics, chemistry and biology suggest that if life can be triggered on Earth by geologic activity, it may also occur elsewhere in the solar system planets, or satellites, under similar conditions. As Enceladus has a large fraction of its mass locked in the form of iced water, it would be a possible target for the search for extraterrestrial organisms. We expect the presence of a sufficient inventory of organics to be present, due to the influx of comets and meteorites. This iced world should be the focus of astrobiology in the distant future. Earlier, we expect to witness the exploration of other iced moons much closer to us.
5.3. The galilean satellites
Still within the outer solar system there are other possible targets for the search for microorganisms. Jupiter has four large satellites, which were discovered by Galileo Galilei in 1610. The second Galilean satellite is slightly smaller than our Moon, but is perhaps the most remarkable potential host of extant extraterrestrial life. It is called Europa. This world is ice-covered. As it is relatively near to Io it is expected to have some volcanic activity in its silicate core. This could be a possible source of heat to melt some of the ice that envelopes its nucleus. For this reason the question of a Europan ocean has been raised and widely discussed. With a large probability there would also be an inventory of carbon and organic compounds. To sum up, Europa may have three ingredients that are known to have played a vital role in the seeding of life on Earth: a source of energy, liquid water and a sufficient quantity of carbon .
5.4. Possible biology experiments in Ganymede and Europa
Ganymede is comparable in size to Titan, which, in turn, is larger than even Mercury. Images released by the two-year long Galileo Europa Mission hint at the presence of an early subsurface ocean . There is also some evidence of the presence of organic material imported by comets and meteorites. In addition, the evidence for a source of energy, a third requisite for the presence of life sometime in the past, is in the form of heat associated with a metallic core. This is known to us by the magnetic field of the satellite which was discovered by the Galileo Mission. Hence, Ganymede is also, like Europa, a good candidate for the search of extraterrestrial microorganisms, in particular for eukaryotes. The Hydrobot/Cryobot mission proposed by a team from the Jet Propulsion Laboratory (JPL), in collaboration with various other centres of research , will attempt to descend onto the ice surface, where there could be some biochemical compounds . There are places on Earth where there are environmental conditions analogous to Europa. An example is found in the Antarctic Dry Valley Lakes. We know that under all these lakes there are eukaryotes, in particular diatoms, surviving in similar conditions that are found in the Europan ocean. This raises the question of what would be a suitable biology experiment in the context of the exploration of Europa. Due to the nature of the Europan environment, the question of designing a biology experiment is radically different from the previous experience in 1976 with the Viking Mission to Mars . Developing a small submersible that could penetrate under the frozen surface of Europa seems now a possibility. Therefore, it is feasible, in principle, to test for the existence of microorganisms. There is a wide variety of possibilities, no doubt many of them with some merit. Yet, we feel that given the difficulty in making some progress in the problem of the distribution of life in the universe, a question of maximum priority is to find out which evolutionary path is being followed by extraterrestrial life. This would help us to ascertain whether the evolution of intelligence is possible via the development of a eukaryotic cell, the pathway that has been chosen by the only example of life that we know so far. Eukaryoticity seems at present the minimum level of complexity needed for a neurone (and eventually for the evolution of a brain and consciousness). Once the eukaryotic level of evolution is reached, multicellularity is bound to follow . For these reasons, out of the many possible biology experiments that are in principle possible in the restricted space that will be available for experiments in the Europa ocean, or other iced satellites, we have argued in the past in favour of at least one biology experiment devoted to the search for the degree of evolution of extraterrestrial microorganisms .
6. DISCUSSION AND CONCLUSIONS
6.1. Is there life elsewhere in the universe?
In spite of the significant progress of the space age, the Earth is the only place where we are certain that life has evolved, producing biodiversity which is remarkable: the smallest coccoid cell-walled microorganisms-the so-called 'nanobacteria'-measure only 80-500 nm [29-30]. Some of the largest living organisms are the Coast redwoods [Sequoia sempervirens (Lamb.) Endl.] that can reach up to 100 m . It should be stressed that there are nine orders of magnitude between the dimensions of these two living organisms. For the question: Is there life in space?, there is still no convincing answer. But the level of research for extraterrestrial microorganisms, and for intelligent multicellular organisms, has increased so much in the last few years that we can only be optimistic about eventual success.
6.2. Some implications of biological evolution
I think it would be useful to reflect on the philosophical consequences of dropping the biocentric point of view , which has been advocated in the past by the evolutionist Ernst Mayr  and the molecular biologist Jacques Monod . Mayr went as far as assigning extraterrestrial life an
"improbability of astronomical dimensions".
On the other hand, Monod believes that:
"The present structure of the biosphere certainly does not exclude the possibility that the decisive event occurred only once".
More recently, the biocentric position has been maintained by the paleobiologist Simon Conway Morris :
"If indeed we are alone and unique, and this possibility, however implausible, cannot yet be refuted, then we have special responsibilities."
Clearly, if we are not alone in the universe, there are some unavoidable theological and philosophical consequences. We feel that the problem of extraterrestrial life is one of the most important questions raised in science to the present. We should reflect on the consequences of a positive result of either finding extraterrestrial microorganisms, or receiving a radio message form an extraterrestrial source: When such discovery occurs, the implications are likely to have an impact on our culture requiring adjustments possibly more radical than those arising form the evidence that humans descend from microorganisms .
1. John Paul II (1992). Discorso di Giovanni Paolo II alla Pontificia Accademia delle Scienze. L'Osservatore Romano, 1st November. p. 8.
2. Julian Chela-Flores (1997). Cosmological models and appearance of intelligent life on Earth: The phenomenon of the eukaryotic cell. In: "Reflections on the birth of the Universe: Science, Philosophy and Theology". Eds. Padre Eligio, G. Giorello, G. Rigamonti and E. Sindoni. Edizioni New Press: Como. pp. 337-373.
3. We borrow a phrase of Gerald Holton cited in ref. .
4. Edward O. Wilson (1998). Consilience The unity of Knowledge. Alfred A. Knopf: New York, pp. 3-7.
5. Logical Positivism intended to exclude from the realm of the cognitively meaningful those statements for which supporting or refuting evidence (satisfactory to scientists and philosophers) can be found. This clearly led to a confrontation with theology.
6. When we refer to the 'Magdalenians', we are using the archaeological classification of south-western Europe and north Africa.
7. William Kelly Simpson, Ed. (1972). The Literature of Ancient Egypt. An Anthology of Stories, Instructions and Poetry. Yale University Press: New Haven. pp. 7-9 and pp. 289 -295.
8. Relevant passages are:
|From the Hymn to the Aten:
8"You created the earth as you wished,
when you were by yourself, (before)
mankind, all cattle and kine,
all beings on land who fare upon their feet
and all the beings in the air, who fly with their wings"
|From Psalm 104:
5"Thou didst set the earth on its foundation,
so that it should never be shaken.
10Thou makest springs gush forth in the valleys;
they flow between the hills,
11they give drink to every beast in the field;
the wild asses quench their thist.
12By them the birds of the air have their
they sing among the branches."