Excerpt from Milan M. Ćirković, The Astrobiological Landscape, Philosophical Foundations of the Study of Cosmic Life, Cambridge University Press, 2012.
In April 1897, Pearson’s Magazine, a rather influential London literary publication, although launched only about a year earlier, published one of the eeriest prologues ever to appear in the world of belles lettres. The author was a 31-year-old former cloth retailer and biology student by the name of Herbert George Wells, who two years before had created a mini-sensation with his first novel, The Time Machine, controversial for both its outrageously speculative scientific premise and for its radical social criticism. Now, he did it again, having started the new novel, The War of the Worlds (to be published in book form the following year), with this dramatic warning:
No one would have believed in the last years of the nineteenth century that this world was being watched keenly and closely by intelligences greater than man’s and yet as mortal as his own; that as men busied themselves about their various concerns they were scrutinised and studied, perhaps almost as narrowly as a man with a microscope might scrutinise the transient creatures that swarm and multiply in a drop of water. With infinite complacency men went to and fro over this globe about their little affairs, serene in their assurance of their empire over matter. It is possible that the infusoria under the microscope do the same. No one gave a thought to the older worlds of space as sources of human danger, or thought of them only to dismiss the idea of life upon them as impossible or improbable. It is curious to recall some of the mental habits of those departed days. At most terrestrial men fancied there might be other men upon Mars, perhaps inferior to themselves and ready to welcome a missionary enterprise. Yet across the gulf of space, minds that are to our minds as ours are to those of the beasts that perish, intellects vast and cool and unsympathetic, regarded this earth with envious eyes, and slowly and surely drew their plans against us.
The famous progressive rock version by Jeff Wayne produced in 1978, gives an even more fascinating introduction by condensing Wells’ second to sixth sentences into ‘Few men even considered the possibility of life on other planets’ – rather frightening in the superb narration of Richard Burton. It is even more pertinent from the point of view of the present book. In The War of the Worlds, Wells, once a pupil of Thomas Henry Huxley, the legendary ‘Darwin’s bulldog’, struck a perfect balance between dramatic and philosophical discourse. The then reigning Kant-Laplace theory about the formation of the Solar System predicted that the planets’ ages correlate with their distance from the Sun, so Mars was considered older than the Earth, which would, in turn, be older than Venus, and so on. The Copernican principle – and naturalism regarding biogenesis! – suggested that, if Mars is habitable at all (and many influential astronomers thought so), it is likely to be the home of a biosphere older in comparison to the terrestrial one. The same Copernican principle, coupled with naturalism with regard to the origin of intelligence (or noogenesis), led Wells to assume the existence of Martians as an intelligent species older than humans. The hallmark Victorian belief in progress in both biological and cultural domains led Wells, and many other thinkers of his day, to translate this greater age into greater intelligence and into greater capacity for manipulating nature, i.e., more advanced technology. However, more advanced technology needs not, and here Wells parted company with many of his optimistic contemporaries, pacify essentially biological – or sociobiological – aggressive instincts of a dominant species. Coupled with the climatic and ecological degradation of their home world (also stemming from the Kant-Laplace theory conjoined with the dominant paradigm of Lyellian gradualism), these instincts led the Martians to undertake the interplanetary expansion and colonization of the nearest habitable ecosystem – our Earth. As noticed by Wells’ protagonist, who is perpetually torn between paralyzing fear and an irrepressible curiosity, while Martian invaders brought horrible destruction and death to humans, they did not seem to act any more irrationally than humans do when clearing a forest in order to cultivate land or irrigating a swamp to build housing. Such actions are not regarded as obviously morally repugnant even today, in this epoch of heightened ecological awareness. In the end, the invasion from Mars fails, but not due to any action of humans – supposed pinnacles of the terrestrial evolution. Instead, the Martians, who are of course well adapted to their own biotic and abiotic environment, are defeated by the simplest terrestrial life forms – bacteria to which they had evolved no resistance, bacteria that have lived on our planets for billions of years, thus prompting again the question whether it is sensible to talk about progress in the context of biological evolution. Consider how deep is the gold mine of philosophical issues (and I mention just the most obvious ones) contained in what is still occasionally – and ignorantly – dismissed as ‘just’ a science-fiction thriller! And it is a contingent fact of history that as a consequence of Wells’ writings more than a few men have hitherto ‘considered the possibility of life on other planets’.
In contrast, consider the plots of recent movies – also fin de siecle, as was Wells’ novel – like Smilla’s Sense of Snow (1997) or X-Files: Fight the Future (1998): a prominent role in both is played by an ancient meteorite that fell to Earth in times past and brought microscopic alien life forms to our planet (both influenced by Robert Wise’s 1971 classic Andromeda Strain, based on the 1969 novel by Michael Crichton). This has been for quite a long time, since Lord Kelvin and Svante Arrhenius, known as the panspermia hypothesis, one of the hotly debated topics in contemporary astrobiology. Now microorganisms, bacteria and viruses, are the invaders from space, if anything more threatening than before. The details of science are, of course, wrong (an interesting question for science, technology and society studies: why is it so difficult to get the science right in any major film?), but the general idea is the same as the one underlying the current efforts of researchers, technologists, and even politicians, to institute efficient planetary protection protocols. The famous Article IX of the Outer Space Treaty, adopted by the United Nations in 1967, explicitly puts the same fear and caution in legalistic terms, by proposing that parties to the treaty
shall pursue studies of outer space including the Moon and other celestial bodies, and conduct exploration of them so as to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter, and where necessary, shall adopt appropriate measures for this purpose.
This admirably non-anthropocentric statute (it lists adverse consequences for other celestial bodies first and those for the Earth after; with good reason we shall return to it in Chapter 6) is just as useful a gauge of our thinking as are the motion pictures mentioned above. Like the discussion of extraterrestrial life at the end of the nineteenth century, in the cultural context it was unavoidably framed by the Schiappareli-Lowell ‘discovery’ of Martian canals, as well as debates on Darwinism vs. other theories of evolution and, last but not least, the late-Victorian anxiety about the conflict of civilizations, so analogous discussions at the end of the twentieth century are coloured by our fear of deadly pandemics, as well as the post-Cold War anxiety about the conflict of civilizations. The difference – and a very real one – consists of the ongoing astrobiological revolution, which has opened wide prospects for an objective assessment of the perennial questions about life and intelligence in their cosmic context. Scientists are understandably reluctant to talk about revolutions in what is usually perceived as day-to-day research work. But an avalanche of both observational and theoretical results from various fields, starting about 1995, being incorporated into a wider synergistic whole, together with large-scale organizational changes and restructuring, give any observer at least some indications that we are living through a real revolutionary epoch. That the revolution could become even more radical, as more and more fields and themes are involved and interconnected, is one of the central topics of this book.
The Canonical Three
But what is astrobiology in the first place? One should not seek a formal definition for many reasons, some of which touch upon philosophical issues, and others are similar to the famous US Supreme Justice Potter Stewart’s statement on obscenity: ‘I know it when I see it.’ Is astrobiology a research activity recognizable on sight? Some of the standard textbooks avoid the question of definition entirely, and pass on to the exposition of a circle of topics that certainly belong to the field. The rationale here is quite clear: after all, the formalization of knowledge – which includes giving precise definitions – usually comes at the end of the original research in a given field, not at the very beginning. The history of science is full of examples: consider why we feel Euclid’s definitions (‘a point is that which has no part’, ‘a line is a breadth-less length’) amusing, even laughable, today. The reason for such a reaction of ours – and, indeed, even of Euclid himself, who did not use the definitions at all in the further discourse on geometry! – is that a definition is useless if it does not reduce a more complex concept to a simpler one. Since, for example, the concept of a ‘part’ is arguably not simpler than the concept of a ‘point’, Euclid’s definition does not help our understanding at all. Because it is clear that simplification cannot proceed indefinitely, it turns out – and the history of philosophy and mathematics confirmed this long ago – some concepts need to be left undefined, as ‘primitives’ of any formal system. Similarly, the proper definition of many other important concepts – even if they can be properly reduced to simpler entities – has had to wait for a long time before the adequate theory of simpler entities was developed. A particularly illuminating example is the concept of number, which was properly defined in the modern sense only after the development of axiomatic set theory in the first decades of the twentieth century – which obviously does not imply that Archimedes or Fermat or Gauss or any other mathematician of old did not know what they were working with. Contrary to the sad prejudice which is forcefully instilled in primary and high-school pupils, formal strictness is much less important in ‘real’ science than in its cardboard (or too often, textbook) version.
In the realm of astrobiology, the strength of the dilemma can be appreciated when we realize that there are literally dozens of definitions of life – which, after all, has been the subject matter of biological sciences for centuries, if not millennia. Like the concept of number, life seems so familiar to us that an intuitive view of it is satisfactory for the vast majority of practical problems. One of the most brilliant minds of modern science, the Austrian physicist Erwin Schrödinger, put it in the title of his epochal 1944 booklet: What Is Life? In contrast to mathematical entities, in the case of life it is the complexity of associated phenomena that causes difficulties for the definitional enterprise. The road Schrödinger and most subsequent researchers took is, therefore, to state the list of properties a system needs to possess in order to be called alive: biochemistry based on polymers such as proteins, metabolism, imperfect reproduction, etc. However, these ‘list definitions’ are, as in other fields, vulnerable to counterexamples, so that a significant amount of the ongoing discussion has been caused by questions such as, ‘Are viruses alive?’ ‘Are prions?’ ‘Are mineral assemblages?’ In order to surmount this difficulty, the so-called ‘NASA definition’ adopted at one of the first astrobiological scientific meetings in 1994, states simply that Life is a self-sustaining chemical system capable of Darwinian evolution. This has been criticized on the basis that it presumes a theory of life (for instance, excluding life based on the strong force, which was speculated about in the fictional context), and presupposes a complete understanding of processes comprising ‘Darwinian evolution’. Both are serious criticisms, closely connected to the issues I shall repeatedly address in the present book, notably the need to fight anthropocentrism. While Wells’ invading Martians are legitimately alive according to the NASA definition, at the very end of this chapter we shall encounter a fictional example of a life form that eminently defies this definition. The normative justification offered by practising astrobiologists is that the exclusion of non-chemical or non-Darwinian entities aspiring to the status of being alive is justified by a constructive belief that such life forms are not possible. This, in turn, motivates some of the critics of the entire astrobiological endeavour, such as biologist Jack Cohen and mathematician Ian Stewart, to charge astrobiology with being narrow-minded and conservative. However, it is generally accepted that the NASA definition and any particular refinement are necessarily provisional, and will evolve as the underlying theory evolves.
The general lesson is that only when it comes to life in a sufficiently novel and strange context – such as when we are discussing biogenesis (the origin of life), or artificial life, or life on other worlds – that the definitional questions come to the fore. Similar reasoning (but understandably more loaded with wider practical, societal and political baggage) applies to the philosophical enterprise of defining intelligence: until the advent of fields touching upon foundational issues, such as artificial intelligence and SETI, few people even paused to ask what, exactly, if anything, is that thing we call intelligence (or consciousness or self-awareness or any number of similar high-level mental phenomena). Thus, we are likely to run into trouble if we try to define astrobiology through a second-order definition, since the concept of life itself is problematic in this respect.
Happily enough, this has been widely recognized in research circles (although not as often or as easily amongst science writers and journalists), and the mainstream approach is nowadays to try to build the understanding of the nature of astrobiological endeavour around wide questions that endeavour is supposed to answer. That is the strategy adopted by NASA in producing its famous ‘Astrobiology Roadmap’, the first version of which was drafted in 1998, and repeated in the 2003 and 2008 editions. The ‘Canonical Three’ are usually listed as:
- How does life begin and develop?
- Does life exist elsewhere in the universe?
- What is the future of life and intelligence on Earth and in space?
A recent anthology of studies about some of the basic issues in the philosophy of astrobiology has clearly identified the tripartite nature of the definition in the very title of the Roadmap: Exploring the Origin, Extent and Future of Life. Its introductory chapter, by Constance Bertka of the American Association for the Advancement of Science (AAAS), gives a simplified, vernacular version of the canonical questions as: Where do we come from? Are we alone? Where are we going? Provided that basic care is taken with the interpretation of the delicate ‘we’ (life forms and intelligent observers, which for the purposes of the second question need to be further specified as having evolved on Earth, though not necessarily originating on it), the simplified version is equivalent to the canonical version above.
And yet, the questions seem to pose interesting dilemmas in their own right. For instance, research into the origin of life falls squarely into the astrobiological domain. This is one of the fields where tremendous progress has been made in the last three decades, leading to new and fruitful concepts such as the RNA-world, which is thought to precede the emergence of metabolism in the first self-replicators. However, the Canonical Three tend to hide that (i) we still do not know to what extent our biogenesis has been influenced by biotic or prebiotic transport from elsewhere in the universe (mixing the first two of the questions); and (ii) we do not know how prevalent ‘our’ type of biogenesis is in the wider spatial, temporal and ensemble-wise context. Suppose, for instance, that near-future space missions discover microfossils of simple life forms on Mars, very similar to terrestrial bacterial fossils, or to those alleged in the controversial August 1996 study by David McKay and collaborators. Since inferring a biochemical detail from microfossils is at best an extremely difficult task, in this scenario (let me call it Areoparadise Lost; I shall return to it in a later chapter), we may still be unable to decide which of the three hypotheses is likely to give the best account of the data: (A) that life originated on Earth and was transported to Mars via meteorites; (B) that life originated on Mars and was transported to Earth via meteorites; or (C) that life emerged independently on Earth and Mars. (I neglect here the possible complication from a ‘higher order’ panspermia hypothesis that life emerged neither on Earth nor on Mars, but perhaps in an interstellar cloud and was transported to both planets via interstellar panspermia.) The last hypothesis implies that life similar to the terrestrial one is likely to emerge quickly wherever the conditions are hospitable for it; this would be an argument for a form of ‘strong convergence’ of viable life forms to something resembling the known terrestrial type. So (C) would, if correct, suggest that the answer to the Canonical #2 would be that we are very likely not alone; but the hypotheses (A) and (B) would preclude any conclusion regarding this question, just as a person seeing her own reflection in a mirror could not infer anything about being alone in the apartment or not. This circumstance does not entail that the probabilities of (A) and (B) being true are equal; it is a difficult empirical question related to the reconstruction of early conditions on Earth and Mars, a correct theory of biogenesis, etc. to decide if it is more likely that life first started on early Earth or early Mars. In contrast, an interesting – and obviously partly philosophical – question is to what degree would each of these alternative hypotheses impact on our wider conclusions; for example, whether we should be optimists or pessimists regarding the probability of success of SETI projects?
This is an example of the ‘foundational’ ambiguities that are part and parcel of astrobiological research, obviously possessing a philosophical dimension. Other such instances become obvious when we look into the intersection of the Canonical Three with classical philosophical puzzles; questions such as What is intelligence? Is there an objective difference between future and past? spring to mind. There is no doubt, however, that in practice the Canonical Three nicely circumscribe the activities intuitively thought of as belonging to the astrobiological realm. The same applies to more formal metrics, such as indexical listings, PACS codes, the scope of relevant research journals and calls for funding, etc. One easily perceives that a surprisingly wide range of disciplinary themes are admitted as belonging to the nascent astrobiological endeavour even by formal (i.e., mostly conservative) criteria of scientific practices and organizations.
Prides and prejudices
The discussion can be illustrated here by a specific ‘live’ research problem. It has been known for quite some time that important biochemical molecules comprising all living matter on Earth can be found in the form of asymmetric stereoisomers, thus exhibiting chirality. Amino acids, the basic building blocks of proteins, are almost exclusively found in form of L-enantiomeres (levo-), building left-handed proteins, while carbohydrates used by living beings, notably sugars, are D-enantiomeres (dextro-). In the non-living world, reflection symmetry is always preserved: on the molecular level, non-living nature does not differentiate between L-and D-forms, and all known prebiotic synthesis pathways produce chiral molecules in 50:50 mixtures. Yet living cells display the most exquisite selectivity. Why would this left-right symmetry be broken in the case of the living world, since it is one of the most general and ubiquitous symmetries in nature? Why is biology asymmetric, while underlying physics and chemistry are symmetric? The origin of this biological homochirality is one of the outstanding puzzles in studies of the origin of life and astrobiology in general; homochirality was even used by Pasteur to define life. One of the active lines of research suggests that amino acids contained in carbonaceous meteorites, like the Murchison meteorite, already possessed an L-enantiomere bias, so that prebiotic Earth could have been seeded by biased molecules, which early life forms inherited. But this approach just shifts the problem to the origin of chiral asymmetry in meteorites. According to an intriguing recent hypothesis, left-handed molecules could have been concentrated if circularly polarized synchrotron light from a rapidly rotating neutron star selectively photolysed right-handed amino acids in a protoplanetary nebula. Thus, a preponderance of their left-handed twins would be created, and subsequently transported to the early Earth. Of course, this and other hypotheses postulating an astrophysical origin for the observed asymmetry have their alternatives in those hypotheses postulating a chance local physical environment on Earth, like asymmetric crystalline surfaces of some clays and minerals. The exciting debate continues at full speed.
Without entering into technical details, it is easy to perceive that symmetry ↔ asymmetry, living ↔ non-living, local ↔ global, in situ ↔ transported, etc. are important axes along which we ‘parse’ natural phenomena, each having significance far outranging the specific problem. This is a hallmark of topics interesting to philosophers of science as well. In addition, the processes of spontaneous symmetry-breaking are currently thought to have generated the predominant part of the complexity of the entire observable universe, including both its physical and biological features. To what extent such symmetry-breakings constitute an argument for the underlying continuity of ‘cosmic evolution’ is a provocative issue I will be returning to in subsequent chapters.
As in the case of all scientific fields, astrobiology presents a constant and complex interplay between theory and data, hypotheses- and model-building on the one side, and experimental and observational work on the other. The essence of the process -at least in those aspects relevant for the present book – can be captured by the ancient metaphor of Ouroboros, the snake eating its tail (Figure 1.1). A favourite alchemical illustration of old, present in The Dialogue of Cleopatra and the Philosophers (a second-century manuscript), and a symbol of self-reflection, is particularly apt here, since even more than in mature fields, the shape and scope of theoretical work is determined by actual reflection upon the often-unexpected observational results, and vice versa. The two semicircular arrows and the ‘natural’ direction we intuitively ascribe to a bilaterally symmetric animal, like a snake, in the figure are intentionally drawn in opposite directions, in order to bring intuitively closer the Heraclitean dictum that ‘the beginning and the end of a circle are one and the same’.
That is, real scientific activity is an entangled mess of both theoretical and observational threads, often connected by nothing stronger than our intuition about where a piece of the puzzle should be in the future grand picture. Thus, in using the metaphor of Ouroboros, we should not be too seduced by it into believing that we could ‘truly’ determine its beginning and end, head and tail. Instead, resembling the mystery of chirality itself, it is a complex network of causes and effects, to which we are too close in both historical and epistemological terms to recognize even a rough global pattern of flow of ideas and knowledge. A purely descriptive historical line of development of astrobiological ideas is also difficult to sketch (Figure 1.2), since the pattern is excessively complex and nonlinear.
The timeline of astrobiological development – such as a subjective one given in Figure 1.2 – teaches us a lesson of the moment: the pace of discovery is accelerating. This dynamic, similar to other accelerating trends in science and technology, like Moore’s law in computer science, poses some interesting questions. In particular, what is the internal dynamic supporting such a tempo of accumulation of knowledge? In computer science, we see that, in retrospect, key discoveries such as integrated circuits, dynamical random access memory, CMOS transistors, have been basic technological (‘internal’) factors in maintaining Moore’s law, together with external factors such as expanding markets for information processing, globalization of economy, etc. To determine these factors in the case of astrobiological development remains a challenge; in contrast to earlier periods, studied by distinguished historians of science such as Michael Crow and Steven Dick, there has so far been very little work done on the ongoing astrobiological revolution.
This is a far cry from saying that astrobiology has not been subjected to considerable criticism, extending from research level through philosophical to popular-science and public outreach levels. Consider the following theses, all of which appear in the contemporary scientific or philosophical discourse, either in published sources or in informal discussions at meetings and conference dinners, and are uttered by informed and educated non-specialist members of the general public. But are they true or false?
• The entire astrobiological enterprise is, so far, an inquiry without a subject, considering that we have no evidence whatsoever of any kind of extraterrestrial life, intelligent or not.
False! The subject of astrobiology is cosmic life, not just extraterrestrial life (disregarding that the notion of ‘extraterrestrial’ is today hard to define clearly, since the Earth is not a closed-box system). Thus, it is eminently clear to modern-day researchers as well as philosophers of science that studies on, for example, biogenesis on early Earth, or mass extinctions in the history of life and their occasional extraterrestrial causes, are also squarely located in the astrobiological domain. To the extent that such research deals with testable hypotheses and its comparison to existing evidence, there is no anomaly in astrobiology compared to other scientific fields. It is visible, inter alia, from the timely appearance of books such as Astrobiology of Earth, or many chapters, reviews, and research articles on the apparently ‘terrestrial’ astrobiological topics. The difficult problem of visibility and accessibility of the primary literature in this epoch of ‘information explosion’ should not impact on the status or the integrity of any particular field; astrobiology cannot be an exception in this regard.
• Astrobiological hypotheses are untestable.
False! Many astrobiological hypotheses are not only testable in principle, but have, in fact, been falsified. For instance, the hypothesis of Alfred Russel Wallace about the location of the Earth and the Solar System in the context of the Milky Way galaxy, suggested in 1903, based on what essentially is an astrobiological argument, has been falsified by the great advances in observational and theoretical astronomy in the 1920s. On the other hand, many hypotheses regarding organic matter in meteorites, for example, have been verified by novel and more sensitive methods of biochemical analysis, which have discovered more and more complex organic compounds. There are many similar examples from recent research – and it is, in contrast, highly mysterious how something that obvious could ever be neglected. The solution probably lies either in artificial and unjustified restriction of the scope of astrobiological research (thus, consequently, missing the central point of the forthcoming synthesis), or in relict positivist – and duly anthropocentric – views on what constitutes an adequate test. Just as the revolution in massive discoveries of extrasolar planets, following the path-breaking events of 1995, was largely unannounced and unexpected in the mainstream astronomy of the 1970s and 1980s, it would be premature to discard the possibility that dramatic development of observational techniques would not enable us to detect habitable or even inhabited planets around other stars. The accelerating trend of discovery also leads to a trend of accelerating returns, at least in some sectors of the astrobiological whole, so we should expect the invention of new and radical methods, enabling new arrays of empirical tests.
• Astrobiology is dull and unoriginal, since it considers only the terrestrial kind of life and neglects a vast realm of quite different possibilities.
False! In fact, astrobiology has from its very inception (and in the works of several illustrious early precursors) encompassed thinking about extremely diverse forms of life. Authors as different as J. B. S. Haldane, Konstantin E. Tsiolkovsky, Carl Sagan, Gerald Feinberg, Stanislaw Lem, Sir Fred Hoyle, Edwin E. Salpeter and Steven Benner, have discursively discussed ideas about life very different from the terrestrial one, in the sense of being based on different biochemistry and incompatible with any terrestrial ecological system. This is too often conveniently ignored. A very disturbing sign of the times and the reigning intellectual standards are that outdated charges are repeated over and over again without deeper analysis. To give just one example, back in 1964, the great palaeontologist George Gaylord Simpson argued that SETI projects are misguided, since the probability of detecting humans or humanoids on other planets are negligible. The argument is based on the arbitrary, and in fact hitherto undermined, assumption that the particular part of biological morphospace corresponding to intelligent or communication-capable beings is congruent with the part of the morphospace corresponding to humanoids. Since the latter is admittedly very small, it follows that the former is also small, and the chances of SETI’s success are, henceforth, minuscule. But there are in fact no empirical or theoretical reasons why the congruence should hold!And yet the criticism is repeated almost verbatim decades later by Frank Tipler, and yet again more recently by Elling Ulvestad – thus contributing, like a self-fulfilling prophecy, to the impression that there is nothing new in SETI studies. Such epicycles need to be dismantled, and it is a philosophical inquiry into the various aspects of astrobiology that offers the best vehicle for the demolition work. Attempts to circumscribe the realm of astrobiology and limit it to the search for a terrestrial kind of life, or for life on terrestrial planets, or for carbon-based life, or to life based on chemical reactions, or even to life based exclusively on our particular low-energy physics are unproductive and will ultimately fail – but the bulk of the work remains to be done.
Notice, however, how antithetical this is to the criticism about ‘inquiry without a subject’ cited above; as many wise people have observed, when X is attacked from diametrically opposed sides, there must be something of worth in X!
• Astrobiology forces a rich naturalist view of life into a straitjacket of mathematical sciences like physics or astronomy.
False! In fact, classical naturalist disciplines, like evolutionary theory and ecology, have been more relevant to astrobiology than ‘ reductionist’ molecular biology insofar as the distinction is worth making at all; this will likely change in the future, as we obtain a much better insight into the biochemistry of the universe at large, but it is still witness to a unifying nature of the new field. Search for life in the universe is necessarily reductionist in the ontological sense, but in no way does it imply any other form of reductionism. We shall see some instances that could be construed as counterexamples for methodological reductionism in this book. In addition, astrobiology in fact opens a staggeringly huge realm of possible diversity for life – it is exactly in this diversity that the narrative of classical natural history may thrive and flourish, perhaps forever beyond a complete mathematical theory. Some of this spirit has again been captured in science fiction; the appropriately titled novel Natural History by Justina Robson is a nice example.
• Astrobiology rests on shaky philosophical and methodological foundations.
True! This is something that could and should be rectified through further work. The pace of developments has been so rapid in the last two decades that it is almost unavoidable to talk about an ‘astrobiological revolution’ – and in times of revolution, urban planning, deep philosophical grounding, and gardening suffer, for good or ill. To this temporal constraint, one should add another problem located along the orthogonal dimension of disciplinary span: just as in similar fields with large (multi)disciplinary spans, like climate science or future studies, it is disturbingly difficult to find the courage to discuss questions that may possibly, even if improbably, lead to the rethinking of each individual discipline’s sacred methodological tenets. Such reluctance shows something of a ‘siege mentality’ of multidisciplinary endeavours, ruled by the common-sense reasoning that, since we have expended much effort in bringing us together, we should not jeopardize this fragile unity by asking possibly awkward questions. A subsequent chapter will discuss why it is – with many other common-sense approaches in science – wrong, since the astrobiological synthesis is, pace relativists of various colours, firmly grounded in nature itself. But, as usually happens, reluctance to pose awkward questions leaves us facing awkward facts, and one such fact is that a gold mine of philosophical and methodological issues in astrobiology is hardly touched by a pick or a drill. The book you are holding is, hopefully, a small step in exactly that direction.
So, why does astrobiology need philosophy? Steven Benner wrote in conclusion of his insightful paper on the definition of life:
Many (and perhaps most) of those scientists who are aware of philosophers on their periphery find their approach not particularly useful. In part, this is undoubtedly because philosophers too often deliver complex, abstruse, and perhaps nihilistic answers to questions that scientists view as concrete… We do what we generally do when a reality is too complex to meet our constructive needs: we ignore it and continue with a simpler, if arguably false, view.
For astrobiologists, a need remains for some pragmatic philosophies of science, if only in the training of our youth. This may best come from those who are practicing astrobiologists… or philosophers closely connected with them… I suspect that an understanding dynamic between theory, observation, and definition will be important to these.
The relationship of the universe and life has for too long been a province of religion and mysticism, so it is not surprising that a sort of cultural reflex has arisen in many scientific circles that regards research projects in these kinds of foundational and ‘deep’ questions as ill-founded, superficial, and generally suspicious. While careful scrutiny is certainly necessary in dealing with such questions, it is in part philosophical scrutiny that is required. While Benner’s pessimistic view may yet turn out to be correct, it is neither necessary, nor should we refrain from philosophical criticism based on a rather poor reputation of the philosophy of science in some circles. Some of the examples presented in this book aim at casting a more positive light on the whole enterprise.
And there is more to it in actual practice. Peter Ward, a distinguished astrobiologist and one of the authors of the ‘Rare Earth’ hypothesis (see Chapter 6), recalls in a somewhat amusing manner his conflicts with the SETI community and his own puzzlement as to how he could be regarded a sceptic when it comes to the search for extraterrestrial life when he is PI on a project which is officially sanctioned as a part of NASA’s astrobiology initiative. The differences he mentions, for instance, between him and Jill Tarter are quite legitimate differences, but his puzzlement can -and should – be explained as a consequence of the deep philosophical divide existing within the astrobiological community as a whole – and, to a degree, even within science in general. Philosophical discourse can help mediate and facilitate critical and fruitful dialogue among different currents of thought within the huge edifice of astrobiological endeavour.
I would go even further and claim that paeans often written – with so many perfectly good reasons – to Charles Darwin and the whole magnificent building of evolutionary thought in biology, are at best incomplete without astrobiological input. This can be seen when, for example, philosopher Timothy Shanahan writes, in the introductory section of his book on Darwinism:
No other scientific theory has had such a tremendous impact on our understanding of the world and of ourselves as has the theory Charles Darwin presented in that book. [on the Origin of Species]. This claim will undoubtedly sound absurd to some familiar with the history of science. Surely the achievements of Copernicus, Galileo, Newton, Einstein, Bohr, and other scientists who developed revolutionary views of the world are of at least equal, if not greater, significance. Aren’t they? Not really. Although it is true that such scientific luminaries made fundamentally important contributions to our understanding of the physical structure of the world, in the final analysis their theories are about that world, whether or not it includes life, sentience, and consciousness. Darwin’s theory, by contrast, although it encompasses the entire world of living things, the vast majority of which are not human, has always been understood to have deep implications for our understanding of ourselves.
[emphases in the original]
His emphasis on the ‘world’ should give us a reason to pause. What, exactly, is the ‘world’ whose understanding is impacted by the Darwinian theory, and how extensive is the ‘world of living things’ to which the theory is applicable? The ‘world talk’ is clearly at the crossroads of philosophy, cosmology and evolutionary biology, the crossroads that astrobiologists naturally tend to regard as home.
Our very disciplinarian culture is a consequence of the ‘unfinished business’ of the Copernican revolution. Chemistry is determined, in the limit of ontological reductionism, by a particular form of low-energy physics. It is necessary to qualify this particular set of laws as being low-energy, since modern physics is largely devoted to transcending these laws and finding the ‘real’ laws, describing in particular the early epochs of the universe, where complete unification of fundamental physical forces could be manifested. We speak of biology as a science of life and psychology as a science of mind, but rarely – if ever – in practice do we qualify or even tacitly understand it as anything but terrestrial life and human mind. But the Copernican revolution should have taught us – if anything – that Earth (and, consequently, its biosphere) is an infinitesimal speck, and that humans should not elevate themselves on a pedestal of being unique, special, or particularly important. Copernicanism in the narrow sense tells us that there is nothing special about the Earth or the Solar System or our Galaxy within large sets of similar objects throughout the universe. In a somewhat broader sense, it indicates that there is nothing particularly special about us as observers: our temporal or spatial location parameters, or our location in other physical, chemical and biological abstract spaces, etc., are typical or close to typical. But how do we proceed to verify that? Although Copernicanism was a guiding light of the great scientific revolutions – and some whose scientific credentials are often doubted, like Freudian psychoanalysis – its status is still somewhat ambiguous. As we shall see in Chapters 3 to 6, some of the best available elucidations linking Copernicanism to the wider physical picture can be correctly ascribed to astrobiology. Moreover, this is a historical consequence of the evolutionary pathway (and our language does point in the right direction here) of human thought about the universe.
Astrobiology already has, for some time, been playing the role of the standard-bearer of Copernicanism, without any specific intention in this regard. As I shall try to show, this could and should be a more intentional and forceful role, one which could not only contribute to the better elucidation of philosophical questions in the philosophy of physics and biology, but also achieve a wider interdisciplinary dialogue and multidisciplinary synthesis. The consequences of this extended mandate are far from being fully understood. In addition, they stand in stark contrast to the misunderstanding, confusion and scepticism that still greet the mention of astrobiology in many circles.
Some confusions arise at the very basic level of broad outlines. Other issues demanding clarification – or whose clarification is too often lost in the noise and excitement – is related to concepts and terms, including their limits. This category is bound to be tightly related to the underlying theories of physics, chemistry, etc. A prototype of this misunderstanding is the question I have often been asked in popular lectures on astrobiology: If you say that we are searching for life in circumstellar habitable zones, what is all that fuss about Europa, Titan or Enceladus, since those bodies definitely do not belong to the Solar System’s habitable zone? Although the question is, of course, easy to answer, and there are textbooks and popular books giving a detailed discussion of the answer and its ramifications, it is still illustrative of the confusion stemming from insufficient attention devoted to insight into the key concepts. Concepts are always rooted in theory, and the double confusion stems from both (i) the sad fact that this old epistemological adage is still insufficiently clear in scientific and lay circles, and (ii) the current situation in which the view of specifically astrobiological theories is foggy, even among the researchers. Similar confusions surround – to a higher degree – concepts such as those of the Galactic Habitable Zone, panspermia hypotheses, mass extinction episodes, as well as many key concepts in SETI studies, such as ‘water hole’ or ‘communication window’, and many others.
The third, and perhaps the ultimate source of misunderstanding as to the nature of astrobiological endeavour, stems from those deep ‘implicit’ assumptions about what is the proper subject matter of scientific research and related activities. I have mentioned the ‘conservative’ criticism of astrobiology that needs to be answered as strongly as possible, since it positively impedes progress in many areas, especially space missions, whose astrobiological components require substantial economic and societal efforts. Here we face another barrier, which is often considered as an impolite topic in scientific circles, namely the role of imagination and a presumed lack of it. In many ways, the ongoing story of astrobiological revolution is the story of imagination (re)gaining its rightful place in scientific endeavour, in an age and atmosphere in which the status of science in wider culture and society leaves much to be desired.
The steam engine was invented in order to pump water out of several coal mines in northern England. It has performed its task in this respect very well, and some of the first models were called the ‘Miner’s Friend’, but hardly anybody apart from historians of technology is aware of that fact today. What we talk about when we mention the steam engine today is how it transformed the entire world by serving as a vehicle – in more than one sense – of the industrial revolution. Similarly, many features of the living world are invented by evolution for one purpose and then adopted for some other function. In a memorable neologism coined by Stephen Jay Gould, we talk about exaptations in such cases, as contrasted with usual adaptations (characters selected for their current utility). In the history of science and technology we are often dealing with exaptations, such as the steam engine. The same phenomenon could apply to whole branches of science. It is, I contend, the evolutionary trajectory of astrobiology itself, while emerging to unify advancing studies of several disciplines related to life in its most general cosmic context, to perform a different, and perhaps vastly more general role of being a herald of wider unity – or consilience – in science, as well as elucidating a vision of the possible cosmic future of humanity (or posthumanity).
Copernicanism and the promise of synthesis
Thus the stage is set. In the remaining chapters, I shall try to muster support for the following tightly interrelated theses:
- The relationship between cosmology and astrobiology is much deeper than it is usually assumed – besides a similarity in the historical model of development of these two disciplines, there is an increasing number of crossover problems and thematic areas that stem from considerations of Copernicanism and observation selection effects.
- Such a crossover area is both visualized and heuristically strengthened by the introduction of the astrobiological landscape, describing complexity of life in the most general context. Modern physical theories dealing with the multiverse add an additional level of detail to what is orthodoxly perceived as astrobiological enterprise, encapsulated in the Archipelago of Habitability.
- Even in its orthodox version, within the well-defined confines of the Milky Way, modern astrobiology offers the prospect of both foundational support and a vast extension of the domain of applicability of the Darwinian biological evolution.
- There is continuity between cosmology, the study of life in its cosmic context, and the study of intelligence, as encompassed by SETI studies – and some of the philosophical arguments act here to undermine traditional scepticism.
- All these issues suggest that we need to look at astrobiological research as embedded in a bigger picture, something which I call the extended mandate of astrobiology, through which a deeper understanding and even consilience can be achieved across a wide spectrum of both scientific and extra-scientific fields (such as the arts).
Although the sketchiness here follows the lack of certainty and sparse nature of the results available thus far, and although the seemingly simple formulation may hide enormous tasks ahead, none should be discouraged by this; after all, pioneers of the Copernican revolution forged ahead with much less. Even meagre successes in this field justify a huge boost in optimism about pushing outward the boundaries of human cognition and understanding. And, of course, I shall approach all issues from the point of view of naturalism, which is at least in part a consequence of the development of a modern philosophy of biology. As David Hull notes: ‘Creationists however, have made one important contribution to the philosophy of science. They have driven home how fundamental naturalism is to science (all science) and not just evolutionary biology.’ Nowhere more than in astrobiology is this requirement more important.
I have begun this chapter with an alien invasion described in fiction, and let me conclude it with another – but hardly more dissimilar. The title of this chapter is, of course, an homage to the celebrated story of Howard Phillips Lovecraft, best known as the horror writer, but also a popular-science writer, a superb amateur astronomer, and a deep thinker whose works contain several astrobiology-related themes. In the eponymous story, written in March 1927, a surveyor for the new reservoir to be built in New England encounters a bleak terrain where nothing will grow; the locals call it the ‘blasted heath’. The surveyor, seeking an explanation for the term and for the cause of the devastation, finally finds an old man, Ammi Pierce, living near the area, who tells him an incredible tale of the events that occurred in 1882. A meteorite had landed on the property of one Nahum Gardner and his family. Scientists who examine the objects find that its properties are bizarre: the substance refuses to cool, displays spectroscopic bands never seen before, and fails to react to conventional solvents. Within the meteorite, a ‘large coloured globule’ is found by drilling: ‘The colour… was almost impossible to describe; and it was only by analogy that they called it colour at all.’ When tapped with a hammer, it bursts. The meteorite itself, continuing anomalously to shrink, finally disappears.
Henceforth, increasingly odd things occur. Nahum’s harvest yields apples and pears huge in size, but they prove unfit to eat; plants and animals undergo peculiar mutations; Nahum’s cows start to give bad milk. (Recall those ‘adverse changes in the environment of the Earth resulting from introduction of extraterrestrial matter’ which Article IX of the Outer Space Treaty warns about.) Then Nahum’s wife goes mad, ‘screaming about things in the air which she could not describe’; she is locked in an upstairs room. Soon all the vegetation starts to crumble to a greyish powder. Nahum’s son Thaddeus goes mad after a visit to the well, and his other sons also break down. Then there is a period of days when Nahum is not seen or heard from. Ammi summons courage to bring policemen, a coroner, and other officials to the place, and after a series of bizarre events they see a column of the unknown colour shoot into the sky from the well; but Ammi sees a small fragment of it returning to Earth. The grey expanse of the ‘blasted heath’ grows by about an inch per year, and no one can say when it will end.
Lovecraft himself considered The Colour Out of Space his best writing, but more as an ‘atmospheric study’ than a classical short story. The alien presence is unknowable, not just to the characters, but to the reader as well. If this life form has any motives, goals, background, etc., they are never revealed. In fact, it is never definitively established that the alien entity is alive or whether it possesses intelligence, intentionality, or any other mental capacity. As Lovecraft scholars S. T. Joshi and David Schultz cogently note: ‘It is precisely because we cannot define the nature – either physical or psychological – of the entities in The Colour Out of Space (or even know whether they are entities or living creatures as we understand them) that produces a sense of horror. ‘ The ambiguity persists even when we close the book; the feeling that our very language is insufficient to deal with the full spectrum of Otherness is hard to shake off.
The Colour forcefully addresses the question many students and educated people ask when first confronted with the astrobiological revolution: why are we dealing with the search for a terrestrial kind of life? The same question is often posed from a sceptical or contrarian perspective, as a challenge: Why don’t you search for different kinds of life, say the one based on XYZ instead of on carbon and water? Is that not tantamount to giving a special position to our form of life, contrary to the Copernican spirit you boast of following? This is a key question that cuts to the core of the effort to make astrobiology independent of our particular anthropocentric and geocentric biases. Lovecraft masterfully posits the situation in which our conventional wisdom and age-old recipes do not work any longer – and suggests that this is indeed what an open-minded researcher is likely to find; a situation to which astrobiology has to be prepared. When Lovecraft’s protagonist concludes, ‘Do not ask me for my opinion. I do not know – that is all’, he does not relinquish any attempt at speculation. Indeed, in the very next paragraph, he dares to suggest that
[i]n terms of matter I suppose the thing Ammi described would be called a gas, but this gas obeyed the laws that are not of our cosmos. This was no fruit of such worlds and suns as shine on the telescopes and photographic plates of our observatories. This was no breath from the skies whose motions and dimensions our astronomers measure or deem too vast to measure. It was just a colour out of space – a frightful messenger from unformed realms of infinity beyond all Nature as we know it; from realms whose mere existence stuns the brain and numbs us with the black cosmic gulfs it throws open before our frenzied eyes.
How really different – barring the lack of equations – is that from the discussions of habitability of universes without weak force, or with different numbers of macroscopic dimensions of space or born in a cold Big Bang? A conscious effort at overcoming anthropocentrism is crucial for both cases.
This is the bold spirit of astrobiology. Establishing conditions for habitability vis-a-vis terrestrial life – even the extreme ends of its ecological spectrum – is an empirical matter; discussing and modelling of conditions for sufficiently different life forms, or even life forms conceivable under different laws of (low-energy) physics, is speculation. Both are – history and philosophy of science teach us – clearly and unavoidably necessary for any successful scientific enterprise. By taking only a slice of the whole mix, as is usually done in popular and journalistic science, or in opinionated presentations of the detractors, we are not only losing the flavour of the enormous complexity of the whole, but we are also missing and downplaying new and unexpected directions for original research.
The author who wrote that ‘[t]he aeons and the worlds are my sport, and I watch with calm and amused aloofness the anticks of planets and the mutations of universes’, and who was called ‘a literary Copernicus’ in a fine essay by Fritz Leiber, is a good companion to have on board on this journey. I shall occasionally return to some other examples of astrobiological topics in Lovecraft’s opus, as well as by other fiction authors, notably Olaf Stapledon and Stanislaw Lem, not only to illustrate the relevant points better, but since here, as elsewhere, artistic imagination has often stumbled upon philosophically and scientifically fruitful ideas.
Excerpt from Milan M. Ćirković, The Astrobiological Landscape, Philosophical Foundations of the Study of Cosmic Life, Cambridge University Press, 2012.