| PoE: Bibliography "S" |
This is the Bibliography "S" page for author's surnames beginning
[Right: George Gaylord Simpson, Paleontologist & Evolutionist, 1902-1984: LÃ©o F. Laporte. See `tagline' quotes below (emphasis italics original, emphasis bold mine), all by Simpson.]
with "S" of books and journals which I may refer to in my book outline, "Problems of Evolution."
Simpson was an a co-founder of the Neo-Darwinian Modern Synthesis, but he had the honesty to admit that the fossil record was not Darwinian!:
"PALEONTOLOGY, once more, furnishes both the most direct evidence for the fact of evolution, and the most imposing evidence against the conception of evolution as a continuous, gradual progression of adaptive relationships. `Gaps in the fossil record' were a serious stumbling block in Darwin's time, and despite the discovery of many missing links - for example the striking completion of horse family history, or the discovery of the bird ancestor Archaeopteryx, with its reptilian features-they still persist. Moreover, they persist systematically: over and over, with suddenness termed `explosive,' a bewildering variety of new types appear: this is true, notably, for example, of the origin of the major mammalian types. Thus, as G.G. Simpson's calculations of rates of evolution show, the bat's wing if evolved by `normal' Mendelian mutation and selective pressure, would have had to begin developing well before the origin of the earth! " (Grene, M.G., 1959, "The Faith of Darwinism," Encounter, Vol. 74, November, p.54).
"At the higher level of evolutionary transition between basic morphological designs, gradualism has always been in trouble, though it remains the `official' position of most Western evolutionists. Smooth intermediates between BauplÃ¤ne [body plans] are almost impossible to construct, even in thought experiments; there is certainly no evidence for them in the fossil record (curious mosaics like Archaeopteryx do not count). Even so convinced a gradualist as G. G. Simpson (1944) invoked quantum evolution and inadaptive phases to explain these transitions." (Gould, S.J. & Eldredge, N., 1977, "Punctuated equilibria: the tempo and mode of evolution reconsidered," Paleobiology, Vol. 3, April, pp.115-147, p.147).
"In example after example, Simpson saw that new groups seemed to appear suddenly in the fossil record. New higher taxa such as whales (mammalian order Cetacea), bats (order Chiroptera), or even the lineage of grass-grazing horses that evolved from leaf-browsing ancestors all made sudden appearances. Seldom was there a long series of intermediate forms that could be traced back through the tens of millions of years that such large-scale evolution would seem to call for. Moreover, Simpson saw that these new groups first appear pretty much in recognizable form. ... As one might expect, they were primitive in certain ways as whales; for example, they bore serrated teeth and still retained a pair of pelvic flippers. But those earliest whales were by no means half-way between a four-legged terrestrial mammalian ancestor and a modern sperm whale. They were much more like the latter than the former. Bats offer an even more dramatic example. The earliest ones known, also from the Eocene Epoch, have not only wings but also the distinctive inner-ear apparatus to show that echolocation had already evolved! And here is the kicker. The earliest whales Simpson knew about are some 55 million years old. If one could devise some sort of measure of rate of evolutionary change, the rate of change within whales over the past 55 million years would seem to be slow to moderate. If that rate were then extrapolated back to encompass the far greater anatomical changes between the earliest whales and their wholly terrestrial, four-legged mammalian ancestors, we would have to place the beginnings of whale evolution hundreds of millions of years back in geological time! And that is a patent absurdity, as placental mammals of any kind had appeared at most only a few tens of millions of years prior to the advent of the earliest whales." (Eldredge, N., 1998, "The Pattern of Evolution," W.H. Freeman & Co: New York NY, Reprinted, 2000, pp.134-135).
PROBLEMS OF EVOLUTION
Â© Stephen E. Jones, BSc. (Biology)
Sagan, C.E., 1973, "The Cosmic Connection: An Extraterrestrial Perspective," Coronet Books: London, Reprinted, 1975.
Sagan, C.E., 1974, "Broca's Brain: The Romance of Science," Coronet Books: London, Reprinted, 1980.
Sagan, C.E., 1977, "The Dragons of Eden: Speculations on the Evolution of Human Intelligence," Ballantine Books: New York NY, Reprinted, 1978.
Sagan, C.E., 1980, "Cosmos," Macdonald: London, Reprinted, 1981.
Sagan, C.E., 1985, "Contact," Pocket Books: New York NY, Reprinted, 1986.
Sagan, C.E., 1994, "Pale Blue Dot: A Vision of the Human Future in Space," Random House: New York NY
Sagan, C.E., 1996, "The Demon-Haunted World: Science as a Candle in the Dark," Headline: London, Reprinted, 1997.
Sagan, C.E., 1997, "Billions and Billions: Thoughts on Life and Death at the Brink of the Millennium," Headline: London.
Sagan, C.E. & Druyan, A., 1985, "Comet," Guild Publishing: London.
Sagan, C.E. & Druyan, A., 1992, "Shadows of Forgotten Ancestors: A Search for Who We Are," Arrow: London, Reprinted, 1993.
Sagan, D., 1990, "Biospheres: Metamorphosis of Planet Earth," Arkana: London, Reprinted, 1991.
Sahlins, M., 1976, "The Use and Abuse of Biology: An Anthropological Critique of Sociobiology," University of Michigan Press: Ann Arbor MI, 1979, Fifth printing.
Savage, J.M., 1963, "Evolution," Modern Biology Series: Holt, Rinehart & Winston: New York NY.
Schick, T. & Vaughn, L., 1995, "How to Think About Weird Things: Critical Thinking for a New Age," Mayfield: Mountain View CA, California, Second edition.
Schmidt-Nielsen, K., 1997, "Animal Physiology: Adaptation and Environment," , Cambridge University Press: Cambridge UK, Fifth edition, Reprinted, 1998.
Schopf, J.W., 1999, "Cradle of Life: The Discovery of Earth's Earliest Fossils," Princeton University Press: Princeton NJ.
SchrÃ¶dinger, E., 1943, "What is Life?: The Physical Aspect of the Living Cell," Folio Society: London, Reprinted, 2000.
Schroeder, G.L., 1990, "Genesis and the Big Bang: The Discovery of Harmony Between Modern Science and the Bible," Bantam: New York NY.
Schroeder, G.L., 2001, "The Hidden Face of God: How Science Reveals the Ultimate Truth," The Free Press: New York NY.
Schroeder, G.L., 1998, "The Science of God: The Convergence of Scientific and Biblical Wisdom," Broadway Books: New York NY.
Schumacher, E.F., 1977, "A Guide for the Perplexed," Harper & Row: New York NY, Reprinted, 1978.
Schutzenberger, M-P., 1996, in "The Miracles of Darwinism: Interview with Marcel-Paul Schutzenberger," Origins & Design, Vol. 17, No. 2, Spring, pp.10-15.
Schwartz, J.H., 1999, "Sudden Origins: Fossils, Genes, and the Emergence of Species," John Wiley & Sons: New York NY.
Scott, A., 1986, "The Creation of Life: Past, Future, Alien," Basil Blackwell: Oxford UK.
Scott, A., 1988, "Vital Principles: The Molecular Mechanisms of Life," Basil Blackwell: Oxford UK.
Searle, J.R., 1984, "Minds, Brains and Science," Harvard University Press: Cambridge MA, 1997, Eleventh printing.
Searle, J.R., 1992, "The Rediscovery of the Mind," MIT Press: Cambridge MA.
Searle, J.R., 1997, "The Mystery of Consciousness: and Exchanges with Daniel C. Dennett and David J. Chalmers," Granta Publications: London, 1998.
Selkirk, D.R. & Burrows, F.J., eds, 1988, "Confronting Creationism: Defending Darwin," New South Wales University Press: Kensington NSW, Australia.
Sermonti, G., 2005, "Why is a Fly Not a Horse?," Discovery Institute: Seattle WA.
Shapiro, R., 1986, "Origins: A Skeptic's Guide to the Creation of Life on Earth," Summit Books: New York NY.
Shapiro, R., 1999, "Planetary Dreams: The Quest to Discover Life beyond Earth," John Wiley & Sons: New York NY.
Sheldrake, R., 1981, "A New Science of Life: The Hypothesis of Morphic Resonance," Park Street Press: Rochester VT, Reprinted, 1995.
Sheldrake, R., 1994, "Seven Experiments that Could Change the World: A Do-It-Yourself Guide to Revolutionary Science," Fourth Estate: London, Reprinted, 1995.
Sheldrake, R., 2003, "The Sense of Being Stared At: And Other Aspects of the Extended Mind," Crown Publishers New York NY.
Shermer, M.B., 1995, "Teach Your Child Science: Making Science Fun for the Both of You," Lowell House: Los Angeles CA.
Shermer, M.B., 1997, "Why People Believe Weird Things: Pseudoscience, Superstition, and Other Confusions of Our Time," W.H. Freeman & Co: New York NY.
Shipman, P. , "Taking Wing: Archaeopteryx and the Evolution of Bird Flight," Simon & Schuster: New York NY, 1998.
Shklovskii, I.S. & Sagan, C., 1977, "Intelligent Life in the Universe," , Picador: London.
Shostak, G.S., 1998, "Sharing the Universe: The Quest for Extraterrestrial Life," Lansdowne: Sydney NSW, Australia.
Shrock, R.R. & Twenhofel, W.H., 1953, "Principles of Invertebrate Paleontology," , McGraw-Hill: New York NY, Second edition.
Shute, E., 1962, "Flaws in the Theory of Evolution," Baker: Grand Rapids MI , Eighth printing, 1980.
Silver, B.L., 1998, "The Ascent of Science," Oxford University Press: New York NY.
Simmons, G., 2004, "What Darwin Didn't Know: A Doctor Dissects the Theory of Evolution," Harvest House: Eugene OR.
Simpson, G.G., 1944, "Tempo and Mode in Evolution," Columbia University Press: New York NY, Third printing, 1949.
Simpson, G.G., 1949, "The Meaning of Evolution: A Study of the History of Life and of its Significance for Man," Yale University Press: New Haven CT, Reprinted, 1960.
Simpson, G.G., 1951, "Horses: The Story of the Horse Family in the Modern World and through Sixty Million Years of History," Doubleday & Co: Garden City NY, Reprinted, 1961.
Simpson, G.G., 1953a, "Life of the Past: An Introduction to Paleontology," Yale University Press: New Haven CT.
Simpson, G.G., 1953b, "The Major Features of Evolution," Columbia University Press: New York NY, Second printing, 1955.
Simpson, G.G. 1960, "The History of Life," in Tax, S., ed., "Evolution After Darwin: The Evolution of Life: Its Origin, History and Future," University of Chicago Press: Chicago IL, Vol. I.
Simpson, G.G., 1964, "This View of Life: The World of an Evolutionist," Harcourt, Brace & World: New York NY.
Simpson, G.G., 1966, "The Biological Nature of Man," Science, Vol. 152, 22 April, pp.472-478.
Simpson, G.G. , ed., 1982, "The Book of Darwin," Washington Square: New York NY, Reprinted, 1983.
Simpson, G.G. & Beck, W.S., 1965, "Life: An Introduction to Biology," , Routledge & Kegan Paul: London, Second edition.
Singer, P., ed., "Ethics," Oxford Readers, Oxford University Press: Oxford, 1994.
Sire, J.W., 1988, "The Universe Next Door: A Basic World View Catalog," , InterVarsity Press Downers Grove IL, Second edition.
Sire, J.W., 1994, "Why Should Anyone Believe Anything At All?," Intervarsity Press: Downers Grove IL.
Slack, A., 1979, "Carnivorous Plants," Doubleday: Sydney NSW, Australia, Second edition, 1981.
Smart, W.M., 1951, "The Origin of the Earth," Penguin: Harmondsworth UK, Reprinted, 1955.
Smith, W., 1984, "Cosmos & Transcendence: Breaking Through the Barrier of Scientistic Belief," Sherwood Sugden & Co: La Salle IL.
Smith, W., 1995, "The Quantum Enigma: Finding the Hidden Key," Sherwood Sugden & Co: Peru IL.
Smith, W., 1988, "Teilhardism and the New Religion: A Thorough Analysis of the Teachings of Pierre Teilhard de Chardin,"Tan: Rockford IL.
Smoot, G. & Davidson, K., 1993, "Wrinkles in Time: The Imprint of Creation," Little, Brown & Co: London.
Sneath, P.H.A., 1970, "Planets and Life," The World of Science Library, Thames & Hudson: London.
Sober, E., 1994, "Conceptual Issues in Evolutionary Biology," , MIT Press: Cambridge MA, Second edition.
Solomon, E.P., et al., 1993, "Biology," , Harcourt Brace: Orlando FL, Third edition.
Southwood, R., 2003, "The Story of Life," Oxford University Press: New York NY.
Spangenburg, R. & Moser, D.K., 1993, "On the Shoulders of Giants: The History of Science from the Ancient Greeks to the Scientific Revolution," Facts On File: New York NY.
Spanner, D.C., 1987, "Biblical Creation and the Theory of Evolution," Paternoster: Exeter UK.
Spencer, H., 1910, "The Principles of Biology," , D. Appleton and Co: New York NY, 2 Vols, Revised.
Spencer, H., 1945, "First Principles," , Watts & Co: London, Sixth edition, Revised.
Spetner, L.M., 1997, "Not by Chance!: Shattering the Modern Theory of Evolution," , Judaica Press: New York NY, Revised.
Sproul, R.C., 1994, "Not a Chance: The Myth of Chance in Modern Science and Cosmology," Baker: Grand Rapids MI.
Spudis, P.D., 1996, "The Once and Future Moon," Melbourne University Press: Carlton South Vic, Australia, Reprinted, 1998.
Srb, A.M., et al., eds, 1970, "Facets of Genetics: Readings from Scientific American," W.H. Freeman: San Francisco CA, W. H. Freeman.
Stahl, B.J., 1985, "Vertebrate history: Problems in Evolution," , Dover: New York NY, Revised edition.
Standen, A., 1950, "Science is a Sacred Cow," E.P. Dutton & Co: New York NY, Reprinted, 1958.
Stanley, S.M., 1981, "The New Evolutionary Timetable: Fossils, Genes, and the Origin of Species," Basic Books: New York NY.
Stanley, S.M., 1989, "Earth and Life Through Time," , W.H. Freeman & Co: New York NY, Second edition.
Stanley, S.M., 1987, "Extinction," Scientific American Books: New York NY.
Stanley, S.M., 1998, "Macroevolution: Pattern and Process," , The Johns Hopkins University Press: Baltimore MD, Revised.
Stannard, R., 1982, "Science and the Renewal of Belief," SCM Press: London.
Stannard, R., 1999a, "The God Experiment," Faber & Faber: London.
Stannard, R., 1999b, "Science and Wonders: Conversations About Science and Belief," Faber & Faber: London.
Stansfield, W.D., 1977, "The Science of Evolution," Macmillan: New York NY, Eighth printing, 1983.
Starr, C. & Taggart, R., 1998, "Biology: The Unity and Diversity of Life," Wadsworth Publishing Co: Belmont CA, Eighth edition.
Stebbins, G.L., 1982, "Darwin to DNA: Molecules to Humanity," W.H. Freeman & Co: San Francisco CA.
Stebbins, G.L., 1966, "Processes of Organic Evolution," Prentice-Hall: Englewood Cliffs NJ, Second printing.
Steele, E. J., 1981, "Somatic Selection and Adaptive Evolution: On the Inheritance of Acquired Characters," , University of Chicago Press: Chicago IL, Second Edition.
Steer, R., "Letter to an Influential Atheist," Authentic Lifestyle: Carlisle UK, 2003.
Sterelny, K., 2001, "Dawkins vs. Gould: Survival of the Fittest," Icon Books: Cambridge UK.
Stevens, S.S. & Warshofsky, F., 1980, "Sound and Hearing," Life Science Library, Time-Life Books: Alexandria VA, Revised edition, First printing.
Stewart, I. & Golubitsky, M., 1992, "Fearful Symmetry: Is God A Geometer?," Blackwell: Oxford UK.
Stewart, I., 2001, "Flatterland: Like Flatland, Only More So," Macmillan: London.
Stewart, I., 1995, "Nature's Numbers: Discovering Order and Pattern in the Universe," Weidenfeld & Nicolson: London.
Stilley, F., 1977, "The Search: Our Quest for Intelligent Life in Outer Space," G.P. Putnam's Sons: New York NY, Second impression.
Stivens, D., 1974, "The Incredible Egg: A Billion Year Journey," Weybright & Talley: New York NY.
Stoner, D.W., "A New Look at an Old Earth," , Harvest House Publishers: Eugene OR, Reprinted, 1997.
Stove, D.C., 1995, "Darwinian Fairytales," Encounter Books: New York NY.
Stove, D.C., 1999, "Against the Idols of the Age," Kimball, R., ed., Transaction Publishers: New Brunswick NJ, Second printing, 2000.
Strahler, A.N., 1992, "Understanding Science: An Introduction to Concepts and Issues," Prometheus Books: Buffalo NY.
Strahler, A.N., 1999, "Science and Earth History: The Evolution/Creation Controversy," , Prometheus Books: Amherst NY, Second edition.
Strickberger, M.W., 2000, "Evolution," , Jones & Bartlett Publishers: Sudbury MA, Third edition.
Stringer, C. & McKie, R., 1996, "African Exodus: The Origins of Modern Humanity," Pimlico: London, Reprinted, 1997.
Strobel, L.P., 2004, "The Case for a Creator: A Journalist Investigates Scientific Evidence that Points Toward God." Zondervan: Grand Rapids MI.
Sullivan, J.W.N., 1938, "The Bases of Modern Science," Penguin: Harmondsworth UK, Reprinted, 1939.
Sullivan, J.W.N., 1933, "Limitations of Science," Pelican: Harmondsworth UK, Reprinted, 1938.
Sullivan, W., 1993, "We Are Not Alone: The Continuing Search for Extraterrestrial Intelligence," , Dutton: New York NY, Revised edition.
Sunderland, L.D., 1988, "Darwin's Enigma: Fossils and Other Problems," , Master Book Publishers: El Cajon CA, Fourth edition.
Swain, H., ed., 2002, "Big Questions in Science?," Jonathan Cape: London.
Swift, D.W., 2002, "Evolution Under the Microscope: A Scientific Critique of the Theory of Evolution," Leighton Academic Press: Stirling UK.
Swinburne, R.G., 1991, "The Justification of Theism," Truth Journal, Vol. 3
Swinnerton, H.H., 1947, "Outlines of Palaeontology," , Edward Arnold & Co: London , Third edition, Reprinted, 1949.
Sykes, B., 2001, "The Seven Daughters of Eve," Bantam: London.
Stephen E. Jones, BSc. (Biology).
My other blogs: TheShroudofTurin & Jesus is Jehovah!
"For the study of these problems it is the great defect of paleontology that it cannot directly determine any of the cryptogenetic factors that must, after all, be instrumental in the evolution of populations. Fossil animals cannot be brought into the laboratory for the experimental determination of their genetic constitutions. The experiments have been done by nature without controls and under conditions too complex and variable for sure and simple analysis. ... On the other hand, experimental biology in general and genetics in particular have the grave defect that they cannot reproduce the vast and complex horizontal extent of the natural environment and, particularly, the immense span of time in which population changes really occur. They may reveal what happens to a hundred rats in the course of ten years under fixed and simple conditions, but not what happened to a billion rats in the course of ten million years under the fluctuating conditions of earth history. Obviously, the latter problem is much more important. The work of geneticists on phenogenetics and still more on population genetics is almost meaningless unless it does have a bearing in this broader scene. Some students, not particularly paleontologists, conclude that it does not, that the phenomena revealed by experimental studies are relatively insignificant in evolution as a whole, that major problems cannot now be studied at all in the laboratory, and that macro-evolution differs qualitatively as well as quantitatively from the micro-evolution of the experimentalist." (Simpson, G.G., 1944, "Tempo and Mode in Evolution," Columbia University Press: New York NY, Third printing, 1949, pp.xvi-xvii).
"As a matter of personal philosophy, I do not here mean to endorse an entirely mechanistic or materialistic view of the life processes. I suspect that there is a great deal in the universe that never will be explained in such terms and much that may be inexplicable on a purely physical plane. But scientific history conclusively demonstrates that the progress of knowledge rigidly requires that no nonphysical postulate ever be admitted in connection with the study of physical phenomena. We do not know what is and what is not explicable in physical terms, and the researcher who is seeking explanations must seek physical explanations only, or the two kinds can never be disentangled. Personal opinion is free in the field where this search has so far failed, but this is no proper guide in the search and no part of science." (Simpson, 1944, pp.76-77).
"Micro-evolution involves mainly changes within potentially continuous populations, and there is little doubt that its materials are those revealed by genetic experimentation. Macro-evolution involves the rise and divergence of discontinuous groups, and it is still debatable whether it differs in kind or only in degree from microevolution. If the two proved to be basically different, the innumerable studies of micro-evolution would become relatively unimportant and would have minor value in the study of evolution as a whole." (Simpson, 1944, p.97).
"If the term `macro-evolution' is applied to the rise of taxonomic groups that are at or near the minimum level of genetic discontinuity (species and genera), the large-scale evolution studied by the paleontologist might be called `mega-evolution' (a hybrid word, but so is `macro-evolution'). The assumption, as in Goldschmidt's work, that mega-evolution and macroevolution are the same in all respects is no more justified than the assumption, so violently attacked by Goldschmidt and others, that microevolution and macro-evolution differ only in degree. As will be shown, the paleontologist has more reason to believe in a qualitative distinction between macro-evolution and mega-evolution than in one between microevolution and macro-evolution." (Simpson, 1944, p.98).
"The facts are that many species and genera, indeed the majority, do appear suddenly in the record, differing sharply and in many ways from any earlier group, and that this appearance of discontinuity becomes more common the higher the level, until it is virtually universal as regards orders and all higher steps in the taxonomic hierarchy. The face of the record thus does really suggest normal discontinuity at all levels, most particularly at high levels, and some paleontologists (e.g., Spath and Schindewolf) insist on taking the record at this face value." (Simpson, 1944, p.99).
"The levels to which these conclusions apply without modification are approximately those discussed as macro-evolution (under that or an equivalent term) by neozoologists and biologists. On still higher levels, those of what is here called `mega-evolution,' the inferences might still apply, but caution is enjoined, because here essentially continuous transitional sequences are not merely rare, but are virtually absent. These large discontinuities are less numerous, so that paleontological examples of their origin should also be less numerous; but their absence is so nearly universal that it cannot, offhand, be imputed entirely to chance and does require some attempt at special explanation, as has been felt by most paleontologists." (Simpson, 1944, pp.105-106).
"This is true of all the thirty-two orders of mammals, and in most cases the break in the record is still more striking than in the case of the perissodactyls, for which a known earlier group does at least provide a good structural ancestry. The earliest and most primitive known members of every order already have the basic ordinal characters, and in no case is an approximately continuous sequence from one order to another known. In most cases the break is so sharp and the gap so large that the origin of the order is speculative and much disputed. Of course the orders all converge backward in time, to different degrees. The earliest known members are much more alike than the latest known members, and there is little doubt, for instance, but that all the highly diverse ungulates did have a common ancestry; but the line making actual connection with such an ancestry is not known in even one instance." (Simpson, 1944, p.106).
"This regular absence of transitional forms is not confined to mammals, but is an almost universal phenomenon, as has long been noted by paleontologists. It is true of almost all orders of all classes of animals, both vertebrate and invertebrate. A fortiori, it is also true of the classes, themselves, and of the major animal phyla, and it is apparently also true of analogous categories of plants. Among genera and species some apparent regularity of absence of transitional types is clearly a taxonomic artifact: artificial divisions between taxonomic units are for practical reasons established where random gaps exist. This does not adequately explain the systematic occurrence of the gaps between larger units. In the cases of the gaps that are artifacts, the effect of discovery has been to reveal their random nature and has tended to fill in now one, now another-now from the ancestral, and now from the descendent side. In most cases discoveries relating to the major breaks have produced a more or less tenuous extension backward of the descendent groups, leaving the probable contact with the ancestry a sharp boundary. None of these large breaks has actually been filled by real, continuous sequences of fossils, although many of them can be exactly located and the transitions described by inference from the improved record on both sides. In addition to the fact that they exist, there are other more or less systematic features of these discontinuities of record that call for attention and require explanation." (Simpson, 1944, pp.107-109).
"In the early days of evolutionary paleontology it was assumed that the major gaps would be filled in by further discoveries, and even, falsely, that some discoveries had already filled them. As it became more and more evident that the great gaps remained, despite wonderful progress in finding the members of lesser transitional groups and progressive lines, it was no longer satisfactory to impute this absence of objective data entirely to chance. The failure of paleontology to produce such evidence was so keenly felt that a few disillusioned naturalists even decided that the theory of organic evolution, or of general organic continuity of descent, was wrong, after all." (Simpson, 1944, p.115).
"J. Arthur Thomson ... felt constrained to devote a considerable part of his work to presentation of proofs of the truth of evolution. This would be a waste of time now. Ample proof has been repeatedly presented and is available to anyone who really wants to know the truth. It is a human peculiarity, occasionally endearing but more often maddening, that no amount of proof suffices to convince those who simply do not want to know or to accept the truth. Reiteration for the sake of these wishful thinkers would be futile, and reiteration for those who do want to know the truth is quite unnecessary because they already know it or can easily find it in earlier works. In the present study the factual truth of organic evolution is taken as established and the enquiry goes on from there." (Simpson, G.G., 1949, "The Meaning of Evolution: A Study of the History of Life and of its Significance for Man," Yale University Press: New Haven CT, Reprinted, 1960, pp.4-5).
THE ORIGIN of life was necessarily the beginning of organic evolution and it is among the greatest of all evolutionary problems. Yet its discussion here will be brief, almost parenthetical. Our concern here is with the record of evolution, and there is no known record bearing closely on the origin of life. The first living things were almost certainly microscopic in size and not apt for any of the usual processes of fossilization. It is unlikely that any preserved trace of them will ever be found, or recognized." (Simpson, 1949, p.14).
"Above the level of the virus, if that be granted status as an organism, the simplest living unit is almost incredibly complex. It has become commonplace to speak of evolution from ameba to man, as if the ameba were a natural and simple beginning of the process. On the contrary, if, as must almost necessarily be true short of miracles, life arose as a living molecule or protogene, the progression from this stage to that of the ameba is at least as great as from ameba to man." (Simpson, 1949, pp.15-16).
"Natural selection as it was understood in Darwinian days emphasized `the struggle for existence' and `the survival of the fittest.' These concepts had ethical, ideological, and political repercussions which were and continue to be, in some cases, unfortunate, to say the least. Even modern students of evolution have not always fully corrected the misconceptions arising from these slogans. It should now be clear that the process does not depend on `existence' or `surviving' certainly not as this applies to individuals and not even in any intensive or explanatory way as it applies to populations or species. It depends on differential reproduction, which is a different matter altogether. It does not favor `the fittest,' flatly and just so, unless you care to circle around and define `fittest' as those that do have most offspring. It does favor those that have more offspring. This usually means those best adapted to the conditions in which they find themselves or those best able to meet opportunity or necessity for adaptation to other existing conditions, which may or may not mean that they are `fittest,' according to understanding of that word. Moreover the correlation between those having more offspring, and therefore really favored by natural selection, and those best adapted or best adapting to change is neither perfect nor invariable; it is only approximate and usual." (Simpson, 1949, p.221).
"It is, however, the word `struggle' that has led to most serious misunderstanding of the process of natural selection, along with a host of related phrases and ideas, `nature red in fang and claw,' `class struggle' as a natural and desirable element in societal evolution, and all the rest. `Struggle' inevitably carries the connotation of direct and conscious combat. Such combat does occur in nature, to be sure, and it may have some connection with differential reproduction. A puma and a deer may struggle, one to kill and the other to avoid being killed. If the puma wins, it eats and presumably may thereby be helped to produce offspring, while the deer dies and will never reproduce again. Two stags may struggle in rivalry for does and the successful combatant may then reproduce while the loser does not. Even such actual struggles may have only slight effects on reproduction, although they will, on an average, tend to exercise some selective influence. The deer most likely to be killed by the puma is too old to reproduce; if the puma does not get the deer, it will eat something else; the losing stag finds other females, or a third enjoys the does while the combat rages between these two." (Simpson, 1949, pp.221-222).
"To generalize from such incidents that natural selection is over-all and even in a figurative sense the outcome of struggle is quite unjustified under the modern understanding of the process. Struggle is sometimes involved, but it usually is not, and when it is, it may even work against rather than toward natural selection. Advantage in differential reproduction is usually a peaceful process in which the concept of struggle is really irrelevant. It more often involves such things as better integration into the ecological situation, maintenance of a balance of nature, more efficient utilization of available food, better care of the young, elimination of intragroup discords (struggles) that might hamper reproduction, exploitation of environmental possibilities that are not the objects of competition or are less effectively exploited by others." (Simpson, 1949, p.222).
"The word `competition,' used in discussion here and previously, may also carry anthropomorphic undertones and then be subject to some of these same objections. It may, however, and in this connection it must, be understood without necessary implication of active competitive behavior. Competition in evolution often or usually is entirely passive; It could conceivably occur without the competing forms ever coming into sight or contact." (Simpson, 1949, p.222).
"It is thus likely, to say the least, that major as well as minor changes in evolution have occurred gradually and that the same forces are at work in each case. Nevertheless there is a difference and many of the major changes cannot be considered as simply caused by longer continuation of the more usual sorts of minor changes. For one thing, there is excellent evidence that evolution involving major changes often occurs with unusual rapidity, although, as we have seen, there is no good evidence that it ever occurs instantaneously. The rate of evolution of the insectivore forelimb into the bat wing, to give just one striking example, must have been many times more rapid than any evolution of the bat wing after it had arisen. The whole record attests that the origin of a distinctly new adaptive type normally occurs at a much higher rate than subsequent progressive adaptation and diversification within that type. The rapidity of such shifts from one adaptive level or equilibrium to another has suggested the name `quantum evolution,' under which I have elsewhere discussed this phenomenon at greater length." (Simpson, 1949, pp.234-235).
"Scientists often display a human failing: whenever they get hold of some new bit of truth they are inclined to decide that it is the whole truth. Thus the neo-Darwinians insisted their natural selection, was the whole truth of evolution; the neo-Lamarckians held that interaction of structure-function-environment was the whole truth; the vitalists saw the whole truth in the creative aspect of life processes; and the finalists found all basic truth in the directional nature of evolution. Similarly, many of the early geneticists, although they soon learned far more about the mechanism involved, accepted de Vries' thesis and concluded that mutation was the whole truth of evolution. Mutations are random, so it was decided that evolution is random. The problem of adaptation was, in their opinion, solved by abolishing it: they proclaimed that there is no adaptation, only chance preadaptation. Other theories had often stumbled over the fact that there is quite plainly a random element in evolution, the nature of which had been unknown. Now the mutationists had identified the source of this random element, but their theory stumbled over the fact that evolution is not wholly random. The vitalists and finalists were right in continuing to insist on this point, although they were wrong in their own overgeneralization of insisting that the directional element is universal and in maintaining that this element is inherent in life or in its goal. The mutationist discoveries were bewildering to many field naturalists and paleontologists, because they in particular were well aware that evolution cannot be a purely random process and that progressive adaptation certainly does occur. For a time the discoveries of the geneticists seemed only to make confusion worse confounded. Defeatism and escapism spread among many students of evolution. One very eminent vertebrate paleontologist ended a lifetime of study of evolution with the conclusion that he did not, after all, know anything about its causes; another decided in the declining years of his prolonged and exceptionally fertile studies of the subject that good and bad angels must be directing evolution! In fact, as the geneticists' studies progressed they were providing the last major piece of the truth so long sought regarding the causes of evolution." (Simpson, 1949, pp.276-277).
"The resulting synthetic theory ... has often been called neo-Darwinian, even by those who have helped to develop it, because its first glimmerings arose from confrontation of the Darwinian idea of natural selection with the facts of genetics. The term is, however, a misnomer and doubly confusing in this application. The full-blown theory is quite different from Darwin's and has drawn its materials from a variety of sources largely non-Darwinian and partly anti-Darwinian. Even natural selection in this theory has a sense distinctly different, although largely developed from, the Darwinian concept of natural selection." (Simpson, 1949, p.277).
"This is not to say that the whole mystery has been plumbed to its core or even that it ever will be. The ultimate mystery is beyond the reach of scientific investigation, and probably of the human mind. There is neither need nor excuse for postulation of nonmaterial intervention in the origin of life, the rise of man, or any other part of the long history of the material cosmos. Yet the origin of that cosmos and the causal principles of its history remain unexplained and inaccessible to science. Here is hidden the First Cause sought by theology and philosophy. The First Cause is not known and I suspect that it never will be known to living man. We may, if we are so inclined, worship it in our own ways, but we certainly do not comprehend it." (Simpson, 1949, p.278).
"Although many details remain to be worked out, it is already evident that all the objective phenomena of the history of life can be explained by purely materialistic factors. They are readily explicable on the basis of differential reproduction in populations (the main factor in the modern conception of natural selection) and of the mainly random interplay of the known processes of heredity." (Simpson, 1949, p.343).
"Man is the result of a purposeless and materialistic process that did not have him in mind. He was not planned. He is a state of matter, a form of life, a sort of animal, and a species of the Order Primates, akin nearly or remotely to all of life and indeed to all that is material. It is, however, a gross misrepresentation to say that he is just an accident or nothing but an animal. Among all the myriad forms of matter and of life on the earth, or as far as we know in the universe, man is unique. He happens to represent the highest form of organization of matter and energy that has ever appeared. Recognition of this kinship with the rest of the universe is necessary for understanding him, but his essential nature is defined by qualities found nowhere else, not by those he has in common with apes, fishes, trees, fire, or anything other than himself." (Simpson, 1949, p.344).
"There really is no point nowadays in continuing to collect and to study fossils simply to determine whether or not evolution is a fact. The question has been decisively answered in the affirmative. There are still those who deny this, of course - there are still some who deny that the earth is round. It is no use gathering more evidence to persuade these doubters, because the evidence already in hand has convinced everyone who ever really studied it. Anyone who cannot or will not accept or attempt to understand this evidence is not likely to have the will or the ability to evaluate new facts of the same sort." (Simpson, G.G., 1951, "Horses: The Story of the Horse Family in the Modern World and through Sixty Million Years of History," The Natural History Library, Doubleday & Co: Garden City NY, Reprinted, 1961, pp.224-225).
"Nevertheless, Darwin's theory still had some serious imperfections that prevented its being accepted by many students of evolution. The theory explained why unfit or inadaptive types of organisms tend to be eliminated, but it did not seem adequately to explain the much more important origin of more fit, better adapted organisms. It also failed to explain why evolution is not completely adaptive-why different types of organisms may evolve even though their relationships with the environment seem to be exactly the same, why adaptation is seldom or never perfect, and why non-adaptive characters (those not involved in adaptation) and inadaptive characters (those opposed to harmonious adaptation) do often arise in evolution. These features of evolution were not well explained by the older forms of Darwinian theory and their reality was abundantly demonstrated by critics of Darwin." (Simpson, 1951, p.293).
"Moreover, it is a fact that discontinuities are almost always and systematically present at the origin of really high categories, and, like any other systematic feature of the record, this requires explanation. ... There remains, however, the point that for still higher categories discontinuity of appearance in the record is not only frequent but if also systematic. Some break in continuity always occurs in categories from orders upwards, at least, although the break may not be large or appear significant to most students." (Simpson, G.G., 1953, "The Major Features of Evolution," Columbia University Press: New York NY, Second printing, 1955, pp.361,366).
"Darwin also considers the argument that the subject of evolution `was in the air,' `that men's minds were prepared for it.' We may note that even if this was so, it would not explain why Darwin was the individual who plucked evolution out of the air or how he accomplished the feat. Darwin himself rejected the argument out of hand because, as he wrote, he `never happened to come across a single naturalist who seemed to doubt about the permanence of species,' and he acknowledged no debt to his predecessors. These are extraordinary statements. They cannot be literally true, yet Darwin cannot be consciously lying, and he may therefore be judged unconsciously misleading, naive, forgetful, or all three. His own grandfather, Erasmus Darwin, whose work Charles knew very well, was a pioneer evolutionist. Darwin was also familiar with the work of Lamarck, and had certainly met at least a few naturalists who had flirted with the idea of evolution. He actually specifies one elsewhere in the autobiography: a Robert Edmund Grant, professor at the University of London. Of all this Darwin says that none of these forerunners had any effect on him. Then, in almost the next breath, he admits that hearing evolutionary views supported and praised rather early in life may have favored his upholding them later." (Simpson, G.G., 1958, "Charles Darwin in search of himself." Review of "The Autobiography of Charles Darwin," by Nora Barlow, ed., Collins: London, 1958. Scientific American, Vol. 199, No. 2, August, pp.117-122, p.119).
"It is a feature of the known fossil record that most taxa appear abruptly. They are not, as a rule, led up to by a sequence of almost imperceptibly changing forerunners such as Darwin believed should be usual in evolution. A great many sequences of two or a few temporally intergrading species are known, but even at this level most species appear without known immediate ancestors, and really long, perfectly complete sequences of numerous species are exceedingly rare. Sequences of genera, immediately successive or nearly so at that level (not necessarily represented by the exact populations involved in the transition from one genus to the next), are more common and may be longer than known sequences of species. But the appearance of a new genus in the record is usually more abrupt than the appearance of a new species: the gaps involved are generally larger, that is, when a new genus appears in the record it is usually well separated morphologically from the most nearly similar other known genera. This phenomenon becomes more universal and more intense as the hierarchy of categories is ascended. Gaps among known species are sporadic and often small. Gaps among known orders, classes, and phyla are systematic and almost always large." (Simpson, G.G., 1960, "The History of Life," in Tax, S., ed., "Evolution After Darwin: The Evolution of Life: Its Origin, History and Future," University of Chicago Press: Chicago IL, Vol. I, p.117).
"The fact-not theory-that evolution has occurred and the Darwinian theory as to how it has occurred have become so confused in popular opinion that the distinction must be stressed. The distinction is also particularly important for the present subject, because the effects on the world in which we live have been distinct. The greatest impact no doubt has come from the fact of evolution. It must color the whole of our attitude toward life and toward our selves, and hence our whole perceptual world. That is, however, a single step, essentially taken a hundred years ago and now a matter of simple rational acceptance or superstitious rejection. How evolution occurs is much more intricate, still incompletely known, debated in detail, and the subject of most active investigation at present." (Simpson, G.G., 1964, "This View of Life: The World into Which Darwin Led Us," in "This View of Life: The World of an Evolutionist," Harcourt, Brace & World: New York NY, p.10).
"The import of the fact of evolution depends on how far evolution extends, and here there are two crucial points: does it extend from the inorganic into the organic, and does it extend from the lower animals to man? In The Origin of Species Darwin implies that life did not arise naturally from nonliving matter, for in the very last sentence he wrote, `...life...having been originally breathed by the Creator into a few forms or into one...... (The words by the Creator were inserted in the second edition and are one of many gradual concessions made to critics of that book.) Later, however, Darwin conjectured (he did not consider this scientific) that life will be found to be a `consequence of some general law'-that is, to be a result of natural processes rather than divine intervention. He referred to this at least three times in letters unpublished until after his death, the one from which I have quoted being the last letter he ever wrote (28 March 1882 to G. C. Wallich; Darwin died three weeks later)." (Simpson, 1964, pp.10-11).
"Until comparatively recently, many-probably most-biologists agreed with Darwin that the problem of the origin of life was not yet amenable to scientific study. Now, however, almost all biologists agree that the problem can be attacked scientifically. The consensus is that life did arise naturally from the nonliving and that even the first living things were not specially created. The conclusion has, indeed, really become inescapable, for the first steps in that process have already been repeated in several laboratories. There is concerted study from geochemical, biochemical, and microbiological approaches. At a meeting in Chicago in 1959, a highly distinguished international panel of experts was polled. All considered the experimental production of life in the laboratory imminent, and one maintained that this had already been done-his opinion was not based on a disagreement about the facts, but depended on the definition of just where, in a continuous sequence, life can be said to begin." (Simpson, 1964, p.11).
"At the other end of the story, it was evident to evolutionists from the start that man cannot be an exception. In The Origin of Species Darwin deliberately avoided the issue, saying only in closing, `Light will be thrown on the origin of man and his history.' Yet his adherents made no secret of the matter and at once embroiled Darwin, with themselves, in arguments about man's origin from monkeys. Twelve years later (in 1871) Darwin published The Descent of Man, which makes it clear that he was indeed of that opinion. No evolutionist has since seriously questioned that man did originate by evolution. Some, notably the Wallace who shared with Darwin the discovery of natural selection, have maintained that special principles, not elsewhere operative, were involved in human origins, but that is decidedly a minority opinion ...." (Simpson, 1964, pp.11-12).
"We feel, almost instinctively, that there is a pattern. The diversity of living creatures is neither complete nor random. All living things share many characteristics, and above this basic level we observe groups with every degree of resemblance, from near identity to great dissimilarity. There is, or seems to be, an essential order or plan among the forms of life in spite of their great multiplicity. There seems, moreover, to be purpose in this plan. The resemblances and differences among a fish, a bird, and a man are meaningful. The resemblances adapt them to those conditions and functions that all have in common and the differences to peculiarities in their ways of life not shared with the others. It is a habit of speech and thought to say that fishes have gills in order to breathe water, that birds have wings in order to fly, and that men have brains in order to think." (Simpson, 1964, pp.190-191).
"A telescope, a telephone, or a typewriter is a complex mechanism serving a particular function. Obviously, its manufacturer had a purpose in mind, and the machine was designed and built in order to serve that purpose. An eye, an ear, or a hand is also a complex mechanism serving a particular function. It, too, looks as if it had been made for a purpose. This appearance of purposefulness is pervading in nature, in the general structure of animals and plants, in the mechanisms of their various organs, and in the give and take of their relationships with each other. Accounting for this apparent purposefulness is a basic problem for any system of philosophy or of science." (Simpson, 1964, p.190).
"Adaptation by natural selection as a creative process and pre-adaptation in the special senses just explained are the answers of the synthetic theory of evolution to the problem of plan and purpose in nature. Of course much work remains to be done, many details to be filled in, and many parts of the process to be more clearly understood, but it seems to me and to many others that here, at last, is the basis for a complete and sound solution of this old and troublesome problem. Adaptation is real, and it is achieved by a progressive and directed process. The process is wholly natural in its operation. This natural process achieves the aspect of purpose without the intervention of a purposer, and it has produced a vast plan without the concurrent action of a planner. It may be that the initiation of the process and the physical laws under which it functions had a Purposer and that this mechanistic way of achieving a plan is the instrument of a Planner-of this still deeper problem the scientist, as scientist, cannot speak." (Simpson, 1964, p.212).
"Our major space agency, NASA, has a `space bioscience' program. Biologists meeting under the auspices of the National Academy of Sciences have agreed that their `first and ... foremost [task in space science] is the search for extraterrestrial life' (Hess et al., 1962). The existence of this movement is as familiar to the reader of the newspapers as to those of technical publications. There is even increasing recognition of a new science of extraterrestrial life, some times called exobiology-a curious development in view of the fact that this `science' has yet to demonstrate that its subject matter exists!" (Simpson, 1964, pp.253-254).
"In the face of the universal tendency for order to be lost, the complex organization of the living organism can be maintained only if work- involving the expenditure of energy- is performed to conserve the order. The organism is constantly adjusting, repairing, replacing, and this requires energy. But the preservation of the complex, improbable organization of the living creature needs more than energy for the work. It calls for information or instructions on how the energy should be expended to maintain the improbable organization. The idea of information necessary for the maintenance and, as we shall see, creation of living systems is of great utility in approaching the biological problems of reproduction." (Simpson, G.G. & Beck, W.S., 1965, "Life: An Introduction to Biology," , Routledge & Kegan Paul: London, Second Edition, p.145).
"We have repeatedly emphasized the fundamental problems posed for the biologist by the fact of life's complex organization. We have seen that organization requires work for its maintenance and that the universal quest for food is in part to provide the energy needed for this work. But the simple expenditure of energy is not sufficient to develop and maintain order. A bull in a china shop performs work, but he neither creates nor maintains organization. The work needed is particular work; it must follow specifications; it requires information on how to proceed." (Simpson & Beck, 1965, p.466).
"As posture is focal for consideration of man's anatomical nature and tools are for consideration of his material culture, so is language focal for his mental nature and his non-material culture .... Language is also the most diagnostic single trait of man - all normal men have language; no other nonliving organisms do. That real, incomparably important, and absolute distinction has been blurred by imprecise use of the word `language' not only in popular speech but also by some scientists who should know better, speaking, for example, of the `language of the bees' ... In any animal societies, and indeed in still simpler forms of aggregation among animals, there must be some kind of communication in the very broadest sense. One animal must receive some kind of information about another animal. That information may be conveyed by specific signals, which may be of extremely diverse kinds both as to form and as to modality, that is, the sensory mode by which it is received. The odor of an ant, the movements of a bee, the color pattern of a bird, the howl of a wolf, and many thousands of others are all signals that convey information to other animals and that, in these and many other examples, are essential adaptations for behavioral integration in the species involved. Human language is also a system of interpersonal communication and a behavioral adaptation essential for the human form of socialization. Yet human language is absolutely distinct from any system of communication in other animals. That is made most clear by comparison with other animal utterances, which most nearly resemble human speech and are most often called `speech.' Nonhuman vocables are, in effect, interjections. They reflect the individual's physical or, more frequently, emotional state. They do not, as true language does, name, discuss, abstract, or symbolize. They are what the psychologists call affective; such purely affective so-called languages are systems of emotional signals and not discourse. The difference between animal interjection and human language is the difference between saying `Ouch!' and saying `Fire is hot.' That example shows that the non-language of animal interjection is still present in man. In us it is in effect not a part of language, but the negative of language, something we use in place of speech. ... . Still we do retain that older system along with our wholly new and wholly distinct system of true language" (Simpson, G.G. , 1966, "The Biological Nature of Man," Science, Vol. 152, 22 April, pp.472-478, p.476).
"Many other attempts have been made to determine the evolutionary origin of language, and all have failed. ... Moreover at the present time no languages are primitive in the sense of being significantly close to the origin of language. Even the peoples with least complex cultures have highly sophisticated languages, with complex grammar and large vocabularies, capable of naming and discussing anything that occurs in the sphere occupied by their speakers. ... The oldest language that can reasonably be reconstructed is already modern, sophisticated, complete from an evolutionary point of view." (Simpson, 1966, p.477).
"D-Days at Dayton is intended to provide judgement on the effects of the trial after 40 years. It contains the contemporaneous accounts of an iconoclastic reporter E.L. Mencken. and the contemporaneous affidavits of the three teachers of science, W.C. Curtis, K.F. Mather and F.-C. Cole. The main offering, however, is a series of eight newly written essays by two ministers, a theologian, three scientists, a scientific journalist, and a former director of the American Civil Liberties Union. Some of these were present at the trial, but none had an active part in it and for some the only connection is that they remember hearing about the trial when they were children. There is also an essay by Scopes himself, and this is extraordinary. Scopes apparently had little interest in the trial at the time, has virtually none now, and is most nearly moved by his belief that Bryan, his rabble rousing, anti-intellectual prosecutor, was `the greatest man produced in the United States since the days
| 1997 Recent Work in Computational Scientific Discovery ||In Proceedings of the Nineteenth Annual Conference of the Cognitive Science Society. Michael Shafto and Pat Langley (Eds.). Mahwah, New Jersey: Lawrence Erlbaum, 1997, pp. 161-166. |
Recent Work in Computational Scientific Discovery Lindley Darden (darden at umd.edu)
Committee on the History and Philosophy of Science, Department of Philosophy
University of Maryland, College Park, MD 20742 USA
Abstract This paper reviews work in computational scientific discovery. After a brief discussion of its history, the focus will be on work since 1990. The second half of the paper discusses the author's use of three methods for studying reasoning strategies in scientific change: historical-philosophical vs. live-in-the-lab vs. computational, pointing out advantages and disadvantages of the computational method. There are a number of approaches to the study of reasoning in scientific discovery. In addition to computational approaches, work continues in cognitive science (e.g., Schunn & Dunbar, 1996), in laboratory studies (e.g., Darden & Cook, 1994; Dunbar, 1995) and in philosophy of science (e.g., Bechtel & Richardson, 1993; Darden, 1991; Kleiner, 1993; Nersessian, 1992; Nickles, 1994; Schaffner, 1993; Spirtes, Glymour & Scheines, 1993). Unfortunately, of the over 200 papers and abstracts submitted for the Philosophy of Science Association meeting in 1996, none were on the topic of reasoning in scientific discovery (Darden, Ed., 1996; 1997). Most philosophers of science do not view discovery as a central topic in the field, despite continuing work by those of us called "friends of discovery" (Nickles, Ed. 1980). It is encouraging that the Cognitive Science Society is sponsoring this Symposium on Scientific Discovery.
This paper will briefly review the history of computational scientific discovery that uses methods from artificial intelligence. (Non-cognitive, non-AI computational work is outside the scope of this paper.) The first part of the paper will concentrate on the work since 1990 (Shrager & Langley, Eds.). The extensive reference list provides a guide for further reading. The second half of the paper will compare three methods used in my own work on reasoning strategies in scientific change. Finally, I will point out advantages and disadvantages of the computational approach from my perspective as a philosopher of science. The study of computational scientific discovery emerged from the view that science is a problem solving activity, that heuristics for problem solving can be applied to the study of scientific discovery in either historical or contemporary cases, and that methods in artificial intelligence provide techniques for building computational systems. Pioneers in this work are Bruce Buchanan (e.g., 1982) and Herbert Simon (e.g., 1977). Buchanan was trained as a philosopher of science at a time when the profession was dominated by Popper's (1965) view that there is no logic of discovery. Buchanan stated the new research program:
"The traditional problem of finding an effective method for formulating true hypotheses that best explain phenomena has been transformed into finding heuristic methods that generate plausible explanations. The problem of giving rules for producing true scientific statements has been replaced by the problem of finding efficient heuristic rules for culling the reasonable candidates for an explanation from an appropriate set of possible candidates" [and finding methods for constructing the candidates] (Buchanan 1985, 110-111). Discovery as heuristic search in a search space enabled AI methods to be applied to discovery tasks.
The first expert system, DENDRAL, was a scientific discovery system. It formed hypotheses about chemical compounds, given mass-spectrographic data (Lindsay, Buchanan, Feigenbaum, & Lederberg, 1980;1993). This was followed by Meta-DENDRAL, which discovered new rules in mass spectrographic analysis, so as to by-pass the problem of getting rules from experts (Buchanan & Feigenbaum, 1978). Although its original algorithm was a computational realization of Lederberg's systematic scan strategy (Lederberg, 1965), DENDRAL was built to carry out a contemporary, difficult scientific task rather than as a model of human cognition.
A more historical-cognitive approach was the aim of the work on BACON, which rediscovered various scientific laws by finding patterns in numerical data (Langley, Simon, Bradshaw & Zytkow, 1987). Simon's early work on finding patterns in sequences (Simon & Kotovsky, 1963) was extended in BACON to heuristic search for patterns in numerical data. The most creative of BACON's abilities was the decomposition of relational data to conjecture intrinsic properties in one or more of the objects engaging in the relations. This step went beyond curve-fitting and was based on the metaphysical assumption that an entity's relational properties are caused by its intrinsic properties. In addition to the data-driven tasks modeled in BACON, the group also investigated theory-driven discovery in STAHL. One wonders to what extent these programs model actual cognitive processes of historical scientists, as opposed to finding strategies which are sufficient to reproduce the historical results. As with most simulations, they provide "how possibly" accounts. Using studies of notebook evidence, the KEKADA system (Kulkari & Simon, 1988) modeled reasoning patterns in some discoveries of the biochemist Hans Krebs and focused on responses to surprising experimental results, helping to dispel the mystery of serendipity in discovery.
A seminal conference on computational methods for scientific discovery, whose proceedings were published in 1990 (Shrager & Langley, Eds.) is a useful source for the state to the field at that time. Some of the pioneers in scientific discovery, e.g., Buchanan, Simon, and Zytkow, push ahead with their research programs. Others who contributed to the 1990 volume are still working on discovery. The American Association for Artificial Intelligence sponsored a Spring Symposium on Systematic Methods of Scientific Discovery in March, 1995. A special issue of Artificial Intelligenceon computational discovery is about to appear, although fewer papers were received than the editors wished (Simon, Valdes-Perez & Sleeman, forthcoming). Data-mining in scientific databases is an active area of research, as are other computational approaches applied to individual sciences, e.g., intelligent systems in molecular biology. It is becoming more difficult to locate computational discovery work because much of it is published in scientific journals--a good sign that the methods of producing results of interest to practicing scientists.
Buchanan (e.g., Lee et al., 1996) continues work on rule induction applied to various scientific databases. Simon is studying the difficult problems of constructing diagrammatic representations (Larkin & Simon, 1987; Qin & Simon, 1995) and of modeling relations between diagrammatic and verbal reasoning (Tabachneck-Schijf, Leonardo, & Simon, 1996). Zytkow continues to work on various aspects of discovery, including analyzing the components needed for an autonomous discovery agent (e.g., Zytkow, 1995/96) and knowledge discovery in databases (e.g., Zytkow & Zembowicz, 1996).
Much of the current work in computational discovery is occurring within applications to particular sciences. According to Peter Karp, the whole field of bioinformatics is doing computational scientific discovery but there is a gradient from computational discoveries that are not based on AI methods, to computational discoveries that are based on AI methods, to methods with a "cognitive flavor." Not much of the bioinformatics work falls into the last category. However, Karp (et al., 1996) applied reasoning by analogy to predict metabolic pathways in the bacterium, H. influenzae,based on the extensive knowledge base that he and Monica Riley, a bacterial geneticist, have developed for E. coli.
Larry Hunter, a frequent editor of publications in AI and molecular biology (e.g., Hunter 1993), recently informed me that there is a clear success is the application of AI technology to molecular biology: hidden Markov models (HMMs) for molecular sequence analysis. They are being applied to automatically build models of families of nucleotide and amino acid sequences. These models are useful as extremely sensitive classifiers of novel sequences, and also generate multiple sequence alignments of large numbers of sequences in a computationally efficient way. Tools based on this approach are now in wide use in the biological community. A review article is Eddy (1996). Also, AI-based qualitative reasoning technologies have produced several good applications in reasoning about metabolism. Perhaps somewhat surprising is that the work in intelligent systems in molecular biology, for the most part, does not employ discovery methods discussed at the Shrager and Langley (Eds. 1990) conference.
The extensive protein sequence database has provided a challenge for those seeking to find computational methods to predict how the linear amino acids will fold into the secondary and tertiary structures in proteins. The Human Genome Project, which is rapidly producing millions of bases of sequence information about both human and model organism genomes, presents a challenge for computational approaches. Good programs are needed for discovering genes, both coding regions and regulatory regions, in these linear sequences. Current programs are not good at finding introns, intervening sequences between the coding regions of genes. Since the genetic system has some means of detecting introns, one can expect computational systems to be able to discover the signal(s). Knowledge discovery in scientific databases (e.g., Fayyad, Haussler & Stolorz, 1996) promises to be an important area in coming years.
Raul Valdes-Perez's (1994) work in chemistry shows the power of computational systems in doing a systematic search of a hypothesis space, given certain constraints. MECHEM is able to find reaction pathways that chemists have missed.
Buchanan's work on rule discovery in scientific databases and Valdes-Perez's work on systematically conjecturing chemical reaction pathways illustrate the power of design AI systems that aim, not at realistically modeling human cognitive capacities, but using computational methods to circumvent human limitations. Humans are not good at searching massive databases and manipulating sets of rules with many features to make predictions. Cognitive science research has shown that humans have a tendency to focus too rapidly on one hypothesis before doing a systematic search of a hypothesis space. Discovery programs that are more systematic and more thorough than humans are an aid to scientists. My own work on reasoning in scientific change focuses on an cyclic process: discovery, assessment, revision. Given a good revision procedure, one's discovery methods can be weaker. Strategies for these processes include: strategies for producing new ideas, e.g., analogies, abstraction instantiation, interfield relations; strategies for theory assessment, e.g., prediction-testing, relations to theories in other fields; and strategies for anomaly resolution (Darden 1991, Ch. 15). After extensive historical study of the development of Mendelian genetics, I proposed hypothetical strategies of the three types. The historical evidence was inadequate to show that they are descriptive cognitive strategies actually used by geneticists. Instead, they are hypothetical strategies that couldhave been used in the historical development of the theory of the gene to produce the changes that didoccur (Darden, 1991). One needs to show that these strategies are effectiveproblem-solving strategies, instances of useful "compiled hindsight" (Darden, 1987), applicable to additional cases, worthy of being used by contemporary scientists or to build AI discovery systems.
I visited in Joshua Lederberg's Laboratory for Molecular Genetics and Informatics and participated in episodes of anomaly resolution that exemplified some of the revision strategies I had proposed (Darden & Cook 1994). One difficulty with the live-in-the lab approach is that little may happen while you are there; fortunately, I was able to observe some anomaly resolution strategies in use. Although I have attempted to implement some of the strategies in AI programs in order to demonstrate their efficacy (e.g., Darden & Rada, 1988; Kettler & Darden 1993; Darden, 1997), I have returned to historical-philosophical work, testing whether strategies from the Mendelian case apply to molecular biology (Darden, 1995).
Computational discovery work has advantages and disadvantages. Finding an adequate knowledge representation for a scientific case is difficult. Early work attempted to represent the relations between genes and chromosomes in part-whole hierarchies and to implement reasoning via inheritance and upward propagation of properties (Darden & Rada, 1988). A much more fruitful method for knowledge representation in genetics was the functional representation (Josephsons, Eds., 1994) for genetic processes (Darden 1997). Furthermore, when one is designing a computational system to rediscover a historical hypothesis, one must navigate between designing a system that trivially reproduces exactly what one is seeking versus designing a system that is unable to accomplish the task at all. Analogy systems often suffer these problems: either the analog is represented in such a way that the system easily finds it or there are so many analogs that the task becomes impossible (for attempts to navigate between these problems, see Kettler & Darden, 1993; Holyoak & Thagard, 1995).
An advantage of computational methods is the precision and completeness that is required to build a working system. The philosopher-historian may neglect aspects that the programmer must specify in detail if the system is to run. A computational approach forces one to reexamine aspects that may be otherwise neglected. However, this advantage is purchased at the price of much time and effort to implement even small parts of a historical case. Various aspects of human discovery, such as the use of pictorial models (e.g., the beads on a string model for genes on chromosomes), provide substantial difficulties when designing an implementation. On the plus side, once one has invested the effort in building a running system, then there is the fun of running experiments, doing "what-if" analyses, testing alternative strategies.
The approach in our TRANSGENE system (Darden, Moberg, Thadani & Josephson, 1992; Darden, 1997) was also used by Karp (1990) in his GENSIM and HYPGEN systems and points to a fruitful way to design a computational discovery system. A qualitative simulator of biological (or other) processes is built and used to make predictions. Data is supplied to test the predictions and another component of the system compares the prediction with data, detects anomalies, and uses diagnosis/redesign strategies to localize the fault in the simulator and redesign a module to remove the anomaly. Perhaps this architecture may be of use in building future AI systems or perhaps more traditional simulation models might be coupled with a revision system to do diagnosis/redesign for anomaly resolution and model improvement.
It will be exciting to see what computational scientific discovery produces in the coming years. The TRANSGENE work was supported by the General Research Board of the University of Maryland and the National Science Foundation Grant No. RII-9003142. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect those of the National Science Foundation. The TRANSGENE system was designed in collaboration with John and Susan Josephson and Dale Moberg; TR.3 was implemented by Sunil Thadani. This paper was written while I enjoyed the hospitality of the Center for Philosophy of Science at the University of Pittsburgh. Very helpful were discussions with, and reprints received from, Bruce Buchanan and Herb Simon. Rapid email responses from Larry Hunter, Peter Karp, and Pat Langley were appreciated. Sets of reprints from Kevin Dunbar, Nancy Nersessian, Tom Nickles, and Jan Zytkow aided me in learning about their recent work. I enjoyed the demo of MECHEM by Raul Valdes-Perez and I profited from his web page:
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| BÄ°OLOGY AND THE PLENATARY ENGÄ°NEERÄ°NG OF MARS ||I. Introduction|
From the perspective of biology, planetary engineering is the ability to alter the environment of a planet so that terrestrial organisms can survive and grow (McKay, 1982). The feasibility of altering planetary environments is clearly demonstrated by mankind's activities on the Earth (Levine, 1991; Fogg, 1995a) and it is increasingly apparent that in the near term future mankind will gain the technological capability to engineer the climate of Mars. Current thought experiments/proposals for the planetary engineering of Mars differ in their methodology, technical requirements, practicality, goals and environmental impact (reviewed and discussed by Fogg, 1995b).
The planetary engineering of Mars may be divided into two distinct mechanistic steps, ecopoiesis followed by terraforming. Ecopoiesis, a term derived by Haynes (1990) which, when applied to Mars, can be viewed as the creation of a self-regulating anaerobic biosphere. On the other hand, terraforming refers to the creation of a human habitable climate (discussed in Fogg 1995b). Whether the creation of such biospheres are possible is not known (Fogg, 1989; Pollack and Sagan, 1993; Fogg, 1995b). However, the majority of these planetary engineering models invoke the use of biological organisms, both during alteration of the planetary environment and in the regulation of the resulting biosphere. This article will briefly review the implications of the current Martian environment and assets for biology and then discuss the relationship between biology and planetary engineering.
II. Current Martian environment and implications for biology
At present the Martian surface environment is effectively sterilizing for all forms of terrestrial organisms (Rothschild, 1990; Mancinelli and Banin, 1995; Dose et al. 1995), although some protected niches may exist above and below the surface of Mars (Friedmann, 1986; Thomas and Schimel, 1991; Boston et al. 1992; Rothschild, 1990, 1995). The properties of the Martian environment that would preclude the survival and growth of terrestrial organisms are as follows (but see also McKay (1982); Rothschild (1990); Banin and Mancinelli, (1995); Mancinelli and Banin (1995)):
1. Low pressure. The atmospheric pressure on Mars (Table 1), mostly due to carbon dioxide, varies from approximately 7.4 to 10 millibar (mbar) (Hess et al. 1980). Extremely low pressure damages organisms and can affect efficient DNA repair (Ito, 1991; Koike et al. 1991).
2. Low temperature. The average diurnal temperature ranges from approximately 170 K to 268 K. During the Martian summer the temperature perhaps rises above the freezing point of water at some equatorial latitudes. From temperature requirements alone, organisms would not be able to survive on present day Mars for a number of reasons: First, the temperatures would completely freeze any organism and depending on the freezing process would cause cellular damage through the formation of ice crystals. Second, such low temperatures would raise the activation energy for enzyme catalyzed processes and thus inhibit biochemical/metabolic reactions. Third, biochemical reactions occur in solution and the transport of metabolites would not occur efficiently in a ice crystals.
3. Water. Liquid water which is a prerequisite for life (McKay, 1991; McKay and Stoker, 1989), under the current Martian atmospheric pressure is unstable. Such extreme dry conditions would cause dehydration, for example damaging DNA (Dose et al. 1995) and leading to mutation and cell/organism death.
4. Radiation. The main source of radiation at the Martian surface is ultraviolet (UV) radiation between the wavelengths of 190 and 300 nm. UV-radiation can be lethal. It is absorbed by nucleic acids (i.e. DNA) and activates the chemical formation of various adjuncts that inhibit replication and transcription of DNA. In the absence of an ozone layer, organisms can only escape the lethal affects of UV-radiation by living in protected habitats. Even those surface organisms which have efficient DNA and cellular repair enzymes would probably perish.
5. Oxidants. Due to the continuous bombardment of the Martian surface with UV-radiation the topmost layer of the regolith is thought to contain strong oxidants which are damaging for cellular components.
6. Carbon dioxide. As mentioned previously the major atmospheric component is carbon dioxide (Table 1). In organisms the relatively high concentration of carbon dioxide would probably cause a low intracellular pH. i.e. acidosis which may be damaging for cellular proteins, cellular components and metabolism (Hiscox and Thomas, 1995).
7. No organic material. Because of the continuous bombardment of UV-radiation and oxidizing conditions, no organic material will be present on the Martian surface (Bullock et al. 1994 and references there in).
8. Table 1. Mars-atmospheric composition and partial pressure of the most abundant gases. (Data from Fogg 1995c, Hiscox 1995 and references therein).
Abundance by Volume
0.04 to 0.2 ppm
III. Biologically useful Martian resources
Undoubtedly the current Martian environment is extremely hostile for terrestrial life. However, Mars does contain sufficient volatiles to enable some form of colonization and perhaps planetary engineering to render environmental conditions more clement for terrestrial life to survive and grow (Meyer and McKay, 1984, 1989; McKay et al. 1991a; Fogg, 1995c; Zubrin, 1995). Analysis of Martian soil and shergottites, nakhlites and chassignittes (SNC) meteorites (believed to have been ejected from Mars (Mustard and Sunshine, 1995 and references therein)) has shown that all of the elements necessary for carbon based life on Earth are present on Mars (Dreibus and Wanke, 1987; Gooding, 1992; Banin and Mancinelli, 1995).
It is evident that Mars once possessed a more clement climate and many observable surface features have been attributed to the presence of liquid water and a dense carbon dioxide atmosphere (Carr, 1986; 1987). Many planetary engineering scenarios (see Fogg, 1995c and references there in) propose that it may be possible to return Mars to an earlier such climate using planetary engineering techniques (with the proviso that such volatiles are still present). Fogg (1995c) suggests that unless impact erosion (Melosh and Vickery, 1989) "blasted" the atmosphere into space then huge quantities of volatiles are still likely to reside on the planet. Over geological history Mars may have lost more volatiles than it gained. For example, water may also have been lost by hydrodynamic escape, atmospheric spluttering and other mechanisms (refer to Carr, 1987; Jakosky, 1991; Kass and Yung, 1995). Therefore returning Mars to a past climatic state may not be possible, and clearly given the climatic history of Mars such a climate maybe geologically unstable and undesirable for the extreme long term habitability of the planet.
A number of compounds and elements are absolutely required for life; liquid water, the so called CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorous and sulfur) are the main elements which constitute amino acids (which make up proteins) and nucleotides (which make up DNA and RNA) and various minerals are also required. All of these elements/compounds are believed to be present on Mars (Banin and Mancinelli, 1995). The amount and location of these resources on Mars is briefly reviewed below. For a more in depth reviews refer to Fogg (1995b,c); Meyer and McKay, 1989, 1991a; and Banin and Mancincelli (1995).
1. Water. Currently, the surface of Mars is devoid of liquid water and the atmosphere only contains minute amounts of water vapor (Table 1)(Carr, 1987). The two main sources of remaining water on Mars are thought to be the north polar cap and the regolith. The quantity of water on Mars is uncertain, and estimates range in order of magnitudes, equivalent to a layer of water over the planet 13 meters (m) to 100 m (Squyres and Carr, 1986).
The north polar cap is composed mainly of water ice (Kieffer et al. 1976). The equatorial regions of Mars appear to be ice poor whereas the heavily cratered terrain pole-ward of Â± 30Â° latitude appears to be ice rich (Squyres and Carr, 1986), with perhaps a conservative estimate of the equivalent of 17 m of ice spread over the surface of Mars (Jankowski and Squyres, 1993). How much liquid water would be necessary, or indeed liberated by either ecopoiesis and/or terraforming has not been determined. However, based on current data, a detailed model for the hydrological cycle on Mars has been proposed (Clifford, 1993) and perhaps this could be adapted for modeling the hydrological cycle during ecopoiesis/terraforming.
Mars will probably never be a wet planet as it might have been in the past (Carr, 1986; 1987), although the view that Mars was "warm and wet" is uncertain and perhaps "cold and icy" may be more appropriate (Kasting, 1991; Squyres and Kasting, 1994). However, there will probably be sufficient water for some type of a biosphere to be established. For certain, the water requirement for ecopoiesis will be several orders of magnitude less than that for a terraformed biosphere. Ultimately, it may be possible to import water onto Mars, for example by the redirection of ice asteroids into the Martian atmosphere to release their volatile components (see Fogg, 1995b). However, although such proposition might be technically feasible, the number of asteroids needed to be diverted is very large.
2. Buried organic material. Bullock et al. (1994) estimate that organic material, either deposited by meteorites and/or remains from an earlier biosphere, maybe between 3 and 40 meters from the surface or perhaps be present in polar regions (Bada and McDonald, 1995). These deposits could therefore be utilized by plants that have long root systems and/or by subsurface microorganisms. However, such scenarios depend on how long it would take thermal waves to penetrate through the ground during planetary engineering.
3. Carbon. On first inspection the two main sources of "trapped" carbon dioxide are as a solid in the polar caps and adsorbed in the regolith. These sources are thought to exchange between 10 and 100 times the current atmospheric pressure of CO2 via the atmosphere and are thus thought to regulate climate change on Mars (Fanale et al. 1982). The permanent cap at the south pole is thought to contain at the most around 10 mbar of CO2 (Fanale and Cannon, 1979) (however this figure is uncertain). Due to the uncertainty in the extent of the Martian regolith, the total mineral surface area exposed to the Martian atmosphere is not known. However, laboratory simulations of the simultaneous adsorption of H2O and CO2 (Zent and Quinn, 1995), where palagonite is used as an analogue of the Martian regolith (Zent et al. 1987), would appear to confirm that the current absorbed inventory of CO2 is 30-40 mbar.
An even greater source of CO2 may be combined in the form of carbonate. Carbonates would have been formed by CO2, present in the early Martian atmosphere, dissolving in water and combining with cations such as Ca2+, Fe2+ and Mg2+ and subsequent precipitates forming carbonates (refer to McKay and Nedell, 1988 and references there in). Warren (1987) suggests that the regolith's low Ca/Si ratio is due to the fact that Ca was removed from the regolith as calcium carbonate. Warren (1987) estimates that perhaps a global shell 20m thick would suffice to remove 1000 mbar of CO2 from the Martian atmosphere. Whether this amount of carbonate is present is not known. However, the layered deposits observed in the Valles Marineris (Nedell et al. 1987) (believed to be an ancient water system) are thought to be derived from the precipitation of 30 mbar of atmospheric CO2 as carbonate in lakes (McKay and Nedell, 1988).
4. Nitrogen. One of the main limiting factors for the growth of "Martian" organisms could be the low abundance of nitrogen (Table 1). No direct analysis of the nitrogen content on the surface of Mars has yet been conducted, the proportion of nitrogen in the Martian atmosphere is shown in Table 1. The abundance of nitrogen on the surface of Mars has been estimated from analysis of SNC data (for example Grady et al. 1995) and it would appear that there is proportionally less nitrogen on Mars than on the Earth (Banin and Mancinelli, 1995). Therefore, from the planetary engineer's perspective it is crucial that forth coming Mars missions investigate the abundance (and perhaps distribution) of nitrogen containing compounds.
5. Minerals. Minerals are also essential for biological process, for example as co-factors in enzyme catalyzed reactions and components of vitamins. All of the elements necessary to support terrestrial life are thought to be present on Mars, although as with the CHNOPS elements their concentration compared to Earth are either slightly higher, lower or the same (Banin and Mancinelli, 1995).
Mineral deposits, carbonates and nitrates etc. may be located in ancient evaporate basins (Forsythe and Zimbelman, 1995) and given suitable locations, i.e. at equatorial latitudes (maximum surface temperature), low point (maximum atmospheric pressure), these may be ideal areas for establishing pioneer ecosystems. Indeed, locations where ancient Martian life may have flourished would contain subsurface organics that have been buried sufficiently deep enough to be protected from oxidation (Zent and McKay, 1994). However, as mentioned above, depending on their depth, these deposits may remain in deep freeze and thus inaccessible for a long periods of time. Locations for ancient Martian life include old oceans along northern planes (Helfer, 1990), ancient ice-covered lakes (Scott et al. 1991; Andersen et al. 1995) and evaporites (Rothschild, 1990). Therefore, site selection to establish these ecosystems may closely resemble site selection for Martian exobiology (Rothschild, 1990; Farmer et al. 1995).
IV. Initial planetary engineering-a biological perspective
For Mars to be less hostile for pioneer organisms initial planetary engineering will be required to increase the atmospheric pressure. This will have a number of effects, including an increase in surface temperature, liquid water will be stable (at least at equatorial latitudes) and an increase in ozone abundance that will reduce the amount of UV-radiation reaching the surface. Perhaps the simplest way to do this, as discussed below, will be to liberate CO2 deposits using a runaway greenhouse mechanism.
1. Runaway greenhouse mechanisms and greenhouse gases. To initiate the runaway greenhouse mechanism for warming Mars, an initial warming is required to release CO2, this will act as a greenhouse gas increasing the global temperature leading to the release of more CO2 and so on (Haynes, 1990; McKay et al. 1991b; Zubrin and McKay, 1993). A number of mechanisms have been proposed to provide this initial warming step. Two techniques being orbiting mirrors to reflect sunlight onto polar regions acting alone or in conjunction with the in situ production of the greenhouse gases such as chlorofluorocarbons (CFCs) (McKay et al. 1991b; Zubrin and McKay, 1993).
Estimates of the lifetime of CFCs in the Martian atmosphere vary from a few days (Levine, 1991-quoted in Fogg, 1992) to 100 years (Zubrin and McKay, 1993). Therefore, if the half-life of CFCs in the Martian atmosphere is small, the production of such quantities of CFCs to warm Mars may be impractical (Fogg, 1992). The Levine estimate of CFC lifetimes maybe an under estimate as this was based on a current Martian environment in which the O3 layer is very small and thus more UV-radiation is available to degrade the CFCs. If solar mirrors could be used to produce an increase in the pCO2 then a greater ozone layer would form (via the photodissociation of CO2) thus increasing the lifetime of the CFCs. However, as Fogg (1992) points out, such CFCs may not co-exist with an ozone layer in a planetary engineered atmosphere, as the photodissociation products of CFCs are thought to react with O3 and therefore reduce ozone coverage. As discussed below, ozone will be important in reducing the amount of UV radiation on the surface of Mars so that terrestrial organisms may exist unprotected on the surface. Instead of using CFCs as a greenhouse gas it maybe possible to use alternative greenhouse agents such as perfluorocarbons (see Fogg, 1995b). However, the toxicity of perfluorocarbons at the concentrations required for warming Mars would have to be determined.
An alternative greenhouse gas for warming Mars could be ammonia (NH3) (Pollack and Sagan, 1991). Ammonia rich asteroids could be diverted towards the Martian atmosphere to release their quantity of NH3 (Pollack and Sagan, 1991; Zubrin and McKay, 1993). However, the probability of locating asteroids that are composed of 100% NH3 is unlikely. The composition of any comet is unlikely to contain more than 10% NH3, therefore the problem is again a matter of scale. Also, NH3 has been shown to be very photochemically unstable in primitive terrestrial atmospheres (which may resemble Martian planetary engineered environments) and NH3 life times are estimated to be from 10 (Kasting, 1982) to 40 years (Kuhn and Atreya, 1979). Therefore the economic cost of importing NH3 containing asteroids might be more than the in situ production of some type of halocarbon to produce an equivalent greenhouse warming. However, as discussed in section six, there maybe a biological solution to this problem.
At a conservative estimate, perhaps only 500 mbar of CO2 is available for release using the runaway greenhouse mechanisms. Based on the work of Kasting (1989; 1991), this would result in a surface warming of approximately 240 K, perhaps bringing temperatures at the equator (during the Martian summer) above the freezing point of water. (Note: Kasting (1989) is based upon a model of the climate of early Earth and assumes a 0.8-bar N2 background atmosphere and a 30% reduction in stellar luminosity- the insulation on Mars is approximately 50% that of Earth). Pollack (1991) estimates that CO2 pressures on the order of several bars were required to raise the annually averaged temperature at low latitudes on an early Mars to values in excess of 273 K and this is also in agreement with the calculations of McKay et al. (1991b) for planetary engineering. Thus using the runaway greenhouse mechanisms of planetary engineering, the climate of Mars would probably be cold and icy rather than warm and wet.
2. Nanotechnology. Alternatively, in concert with the previous techniques or alone, nanotechnology may be employed for planetary engineering (Morgan, 1994; Nussinov et al. 1994) . For example in the liberation of carbon dioxide from carbonate deposits (Nussinov et al. 1994). Great claims are made to the potential exponential growth of nano-robots (Freitas, 1983; Morgan, 1994). Morgan (1994) has suggested that nano-robots could contain structures similar to those found in biological organisms. In common with microorganisms, nano-robots may have a huge growth capacity, i.e. doubling time, which for some bacteria, growing under ideal conditions, can be as little as 20 minutes. Ideal growth conditions for nano-robots are therefore likely to resemble those found for microorganisms (see Figure 1.). However, conditions on Mars will not be ideal for grow of either microorganisms or nano-robots. Nutrients/substrates may vary in abundance, there may be competition for resources etc. Therefore, growth is likely to be linear rather than exponential (Figure 1). Also, unlike biotechnology, nanotechnology has not been demonstrated.
Figure 1. Growth curves of "organisms" (either microorganisms or nano-robots) on Mars. (A) Is the lag phase in which the "organisms" are growing at a slow rate. In microorganisms this caused by the "turn on" of genes to make new proteins etc. If conditions are optimal, i.e. abundant substrate/nutrients, and remain optimal, then growth rate becomes exponential (E). However, if ecological climax is reached, e.g. the substrate pool becomes limiting, then the population crashes (D1). A far more likely scenario is that the initial number of "organisms" grows slowly (B) as the distribution of substrates will not be uniform. Eventually, the number of organisms "living" will equal the number of organisms "dying" (C). If the substrate becomes limiting or environmental conditions worsen (i.e. drop in temperature) then the number of organisms will drop (D2). As conditions become more favourable then growth resumes (A). For Mars, the ideal growth curve for any organism should follow (A to C or D2). This idea of keeping growth rates below climax has been rightly argued by Fogg (1995b).
3. Nuclear mining and alternative planetary engineering mechanisms. There are a number of mechanisms available for liberating the carbon dioxide "trapped" as carbonates, including cometary impact (Fogg, 1989 and references there in) and nuclear mining (Fogg, 1989; 1992; Pollack and Sagan, 1991). Such anthropogenic mechanisms of planetary engineering become attractive if there is insufficient volatile inventory for a runaway greenhouse mechanism. The environmental consequences of radioactive fall out associated with certain forms of nuclear mining could be quite severe (Haynes and McKay, 1992), leading perhaps to widespread mutation and death of organisms. Given an advanced technology (more than that required for ecopoiesis) it may be possible to release carbon dioxide in carbonate deposits by volcanic means. The thermal erosion of carbonates has been hypothesised as a mechanism for the recycling of carbon dioxide into the atmosphere of early Mars (Schaefer, 1993).
4. Ozone. One of the main functions of initial planetary engineering would be to increase the ozone layer thus providing shielding of organisms from UV-radiation (Hiscox and Lindner, 1996). Based on O3 estimates in a Precambrian atmosphere, the minimum ozone column being tolerable by unprotected bacteria would fall between 1x1018 and 4x1018 cm2 depending on the bacterial species being considered (Francois and Gerard, 1988). Fortuitously, oxygen is not required to generate an ozone layer, instead the photodissociation of CO2 might be used to generate sufficient ozone to provide an ozone layer (Hiscox and Lindner, 1996). Such a scenario may be self-regulating (Figure 2).
Figure 2. Diagrammatic representation of an ozone "cycle" during planetary engineering. (Interactions at the poles are complex and thus for simplicity are not represented). Ozone is created by the photodissociation of carbon dioxide. Through vertical mixing this reaches the lower atmosphere where it is destroyed by water, which has been released from the regolith by heating either with solettas (Birch, 1992) and/or greenhouse gases (McKay et al. 1991b). (Note: the hypothetical greenhouse gases used in this scenario do not chemically react with ozone. More carbon dioxide is released leading to the formation of new ozone and so on.
If only a minimum ozone coverage is created by planetary engineering (sufficient to provide shielding against lethal UV-radiation for most organisms), on some occasions the ozone level may drop below a threshold level. Thus exposed organisms may be exposed to lethal levels of UV-radiation on Mars. Seasonal and latitudinal variations in dust and cloud opacities have induced as much as a 40% variation in ozone on a seasonal and latitudinal basis (Lindner, 1988). In addition, the asymmetry in dust and cloud opacities at late winter in each hemisphere could also cause a 10-20% hemispherical asymmetry in ozone (Lindner, 1988). Therefore a mechanism of preventing this drop in ozone would be preferable. The current dust concentration in the Martian atmosphere can induce a 10-50% increase in ozone abundances because photodissociation rates are greatly reduced by dust absorption (Lindner, 1988) and this phenomena has been observed in the polar regions of Mars, where dust absorbs or scatters to space most UV-radiation before it strikes the cap (Lindner, 1990).
Therefore a planetary engineering mechanism that can create such a dust storm would be useful in providing additional protection to organisms by reducing the amount of UV-radiation reaching the surface. First by providing direct shielding against UV-radiation and second by inducing localised increases in the production of ozone, thus restoring an ozone layer. One mechanism to generate a global dust storm may be heating of the polar regions with space based sunlight reflectors (Zubrin and McKay, 1993) (abbreviated to SBR). Similar to what occurs on Mars at the moment, the asymmetric heating of one pole would cause a pressure differential i.e. wind, and this would carry dust. However, if the polar reserves of carbon dioxide and water are liberated early in planetary engineering then an alternative mechanism is required. Such a mechanism could be the heating of a near by dusty area on Mars by a SBR (Hiscox and Lindner, 1996). This may cause a localised dust storm which would provide local UV-radiation coverage by plugging the nearby ozone hole. Satellites could be used to monitor atmospheric ozone abundances and warn of impending ozone "holes".
5. Temperature/humidity. Different microbial species vary widely in their optimal temperatures for growth. The upper end of temperature range tolerated by any given species correlates well with the general thermal stability of that species' proteins. Microorganisms share with plants and animals the heat shock response, a transient synthesis of a set of "heat shock proteins" when exposed to a sudden rise in temperature above the growth optimum. These proteins appear to be unusually heat resistant and act to stabilise the heat sensitive proteins of the cell. However, beyond a certain temperature proteins will irreversibly denature and therefore enzymes (which are mostly composed of proteins) will become non-functional. Some bacteria can also exhibit cold shock, the killing of cells by rapid as opposed to slow cooling. For example, rapid cooling of Escherichia coli from 310 to 278 K will kill 90% of the cells. Early stages of planetary engineering will probably require psychrophilic forms, i.e. those that grow best at low temperatures (normally 288-293 K).
In order to define a minimum temperature and humidity for pioneer microorganisms to grow during ecopoiesis one can study microorganisms that inhabit regions on the Earth that best approximate regions on Mars. Apart from the greater pressure and less UV-radiation, the cold dry Ross Desert regions of Antarctica best approximate Mars (Friedmann and Weed, 1987; McKay, 1993). Yet these regions are host to a variety of microorganisms which live just under the surface of rocks and these are called endolithic microorganisms (Friedmann, 1982). In these regions air temperatures range between 258 K and 273 K in the summer and may drop to near 213 K in the winter, with relative humidities ranging from 16 to 75 percent (Friedmann, 1982 and references there in). Before planetary engineering, Mars will be colder than Antarctica, however, as discussed above, using the greenhouse mechanism it may be possible to raise the surface temperature of Mars to conditions resembling Antartica.
Microbial activity in the Antarctic cryptoendolithic habitat is regulated by temperature (Nienow et al. 1988a) and metabolic activity is possible only when solar radiation raises the temperature of the rock above 263 K (Nienow et al. 1988b). Therefore the minimum Martian surface temperature required for ecopoiesis, should 263 K or greater (at least in regions were organisms will be seeded).
Cryptoendolithic lichens begin photosynthesis when the matric water potential is -46.4 megaPascals (MPa) which corresponds to a relative humidity of 70% at 281 K, whereas cryptoendolithic cyanobacteria photosynthesize at high matric water potentials of -6.9 (and greater) (a relative humidity of 90% at 281 K) (Palmer Jr. and Friedmann, 1990). Alternatively, both may use melt-water as a source of water rather than water vapour which is used in times of environmental stress. Therefore, if melt water is unavailable for pioneer microorganisms, the relative humidity should be at least 70%, perhaps lower if genetic engineering (see below) can be used to increase tolerance to desiccation. Alternatively, pioneer microorganisms could be adapted to tolerate desication (Friedmann, 1995-personal communication in Hiscox and Thomas, 1995), and this is perhaps a more feasible mechanism than genetic engineering.
6. Growth and diversity. After the introduction of microorganisms into a partially altered Martian environment the growth rate will exceed the death rate and therefore there should be a net accumulation of microorganisms. However, once the new biosphere becomes established the population of microorganisms in a stable biosphere will be roughly constant, i.e. growth is balanced by death. The survival of any microbial group within its niche is determined in large part by successful competition for nutrients and by maintenance of a pool of living cells (or dormant cells) during nutritional deprivation. In a constantly changing environment, as will occur during planetary engineering, the proportion of living bacteria to dead bacteria may vary dramatically (Figure 1).
V. Candidate biological methods and mechanisms for adapting terrestrial organisms to grow on Mars
A number of pioneer microorganisms and plants have been proposed for introduction onto a partially altered Mars (Averner and MacElroy, 1976; Friedmann and Ocampo-Friedmann, 1994; Hiscox, 1995; Hiscox and Thomas, 1995; Fogg, 1995d). The first organisms will of necessity be photoautotrophic (Haynes and McKay, 1992), which means that they utilise sunlight as an energy source and do not require complex organic material for metabolism (which would be absent on the surface of the planet prior to the introduction of terrestrial microorganisms-see section two). In order to aid organisms to survive and more importantly grow as soon as physically possibly on a partially altered Mars, two main mechanisms of adaptation can be utilised either individually or in concert, that of genetic manipulation and/or directed selection under simulated Martian conditions (Hiscox, 1995; Hiscox and Thomas, 1995) (Figure 3):
Figure 3. Schematic representation of selecting organisms for growth on Mars. Candidate organisms could perhaps be isolated from extremes of environments on the Earth that in some respects resemble the partially altered environment on Mars. The organisms could be further adapted to Mars by either genetic engineering and/or selection in Marsjars. Once environmental conditions become more clement on Mars, organisms could be directly introduced from the Earth with minimum adaptation. (The stage at which organisms could be introduced onto Mars is indicated by the right-hand path). (Taken from Hiscox, 1996).
1. Genetic engineering. Genetic engineering is now common place and the ability to manipulate organisms for Mars, especially prokaryotes and also eukaryotes is entirely feasible (Hiscox, 1995). For example, a pioneer microorganisms's tolerance to lower intracellular pH could be increased by engineering in a gene(s) from another organism that confers tolerance to low pH (Hiscox and Thomas, 1995). Such an organism would then be termed recombinant, or in this case a genetically engineered Mars organism (GEMO; Hiscox, 1995). One danger in introducing new genes into an organism is that the over expression of such a gene may lead to deficiencies in other key metabolites, therefore the inter-conversion of biosynthetic components has to be tightly regulated (Hiscox, 1995; Hiscox and Thomas, 1995).
2. Genetic selection. Alternatively, organisms could be adapted for growth on a partially altered Mars by growing them under simulated environmental conditions that increasingly resembles the climate on Mars at the proposed time of their introduction. In genetic terms, this process is called directed selection and is a well known Darwinian concept. In which adaptation results from the systematic relationships between genotype and phenotype and between phenotype and reproductive success in a given environment. There are limits to increases in both physiological and metabolic processes using selection, and thus genetic engineering could be used to increase some of these. Because of their fairly rapid generation time, microorganisms would best lead themselves to this type of adaptation.
A number of studies have grown various terrestrial microorganisms under different combinations of Martian or extreme terrestrial/non-terrestrial environmental conditions (for example see: Ito, 1991; Koike et al. 1991; Moll and Vestal, 1992) and the growth on Mars of a blue-green algae has been modelled (Kuhn et al. 1979). It is certainly feasible to conduct Marsjar simulations using terrestrial microorganisms and such experiments would provide data for the growth of terrestrial organisms in Martian greenhouses and planetary protection issues. Indeed many of these types of experiments have already been proposed for planetary protection issues (Lindberg and Horneck, 1994). The only factor of a Martian environment that would be difficult to simulate is the effect of gravity.
A fine balance between survival and evolutionary potential has to be struck by organisms that have the efficient ability to remove most errors in DNA replication. In general, an organism with perfect replication will never evolve, although genetic recombination (gene swapping) may still occur and act as a mechanism for evolution (and is perhaps the major driving force!). Whereas an organism with a highly error-prone mechanism would not survive. The error repair mechanism in bacteria is so accurate that an error is generated only once in 108 to 109 bases (a base is a unit of a chromosome). Because the genomes of bacteria are about 4.5 million bases long, only about 1% of the progeny have alterations in their base sequence. This error level can be easily tolerated, it also continuously generates variants that can be selected under specialised conditions. One must bear in mind that selection is always for survival, a given species has no advantage in evolving into a different species. Natural selection tends to promote the divergence of populations living in different environments. Radical changes in the habitat, as will occur during planetary engineering, will often exterminate a species, therefore organisms will have to be able to adapt to these changing circumstances.
It is increasingly evident that many microorganisms exist in consortia formed by representatives of different genera. Other microorganisms often characterised as single cells in the laboratory form cohesive colonies in the natural environment. This property of organisms will be important during Marsjar simulations and subsequent introduction onto Mars.
3. Safety issues of genetic engineering. Almost certainly GEMOs/selected organisms will be released on the surface of Mars, either through contamination associated with manned exploration, colonist's greenhouses or the deliberate release during a planetary engineering effort. These organisms will be growing under conditions that do not occur on the Earth, and therefore their evolution may proceed in a completely novel manner compared to their counterparts on the Earth (Haynes, 1990). For example, non- pathogenic bacteria may become pathogenic. Such considerations are especially important if terraforming is realised and the human population will inhabit the surface of Mars, although many genetic safeguards can be built into such organisms (Hiscox, 1995).
VI. Uses of terrestrial organisms on Mars
Terrestrial organisms will serve a number of purposes, both during and after planetary engineering:
1. Increase in atmospheric pressure and change in chemical composition. For example, microorganisms could be used to release carbon dioxide from carbonate deposits (Friedmann et al. 1993) and nitrogen from nitrate deposits (Thomas, 1995; Hiscox and Thomas, 1995) and appropriate deposits could be determined from orbit (Hiscox, 1995). In order to terraform Mars, McKay (1982) and McKay et al. (1991b) proposed that plants could be used to convert the mainly carbon dioxide atmosphere formed during ecopoiesis into an oxygen atmosphere. For example, Fogg (1992) estimates that 5.7x1017 kg of biomass would have to be sequestered as part of the biological production of 158 mbar of oxygen. Also, Fogg (1995d) has addressed some of the issues and suggests a number of solutions for growing plants in low oxygen concentrations that would be present during early stages of ecopoiesis i.e. below an oxygen pressure of 20 mbar.
It should be noted that previous estimates of the time taken to convert a mainly carbon dioxide atmosphere into an oxygen atmosphere may be underestimates as these calculations did not take into account the possible increase in respiring aerobic organisms (i.e. lichen, bacteria etc.) that may concomitantly increase in numbers with more oxygen availability and result in the production of more carbon dioxide. Therefore, biology on Mars must be actively held away from ecological climax in order to maximise oxygen production and minimise its uptake (Fogg, 1995e).
One should note that if plants are to be used to convert the mainly carbon dioxide atmosphere into an atmosphere suitable for human habitation, then in the early stages of this process all such plants should be either self or wind pollinating. Self pollination would probably be the preferred option as wind pollination may be extremely inefficient if the population density of plants is too low. These two mechanisms of pollination are required because the carbon dioxide atmosphere will be too toxic for insects that pollinate plants.
2. Climate regulation and control. Organisms will help maintain the gaseous composition of the Martian atmosphere and thus regulate climate. After planetary engineering, organisms such as plants will also affect climate by cycling vast amounts of water. An example is provided by Amazonia, which contains two-thirds of all above ground freshwater on Earth. At least half of Amazonia's moisture is retained within the forest ecosystem, being constantly transpired by plants before being precipitated back into the forest, with a mean cycling time of 5.5 days (Salati and Nobre, 1992).
3. Control of albedo. Sagan (1973; 1980) proposed that plant growth could be used to lower the albedo of the Martian polar caps thus increasing their absorption of solar radiation and heating them, thus hopefully triggering a runaway greenhouse effect. (This scenario has one main problem in that metabolic reactions do not occur at the temperatures found on the Martian polar caps). However, the idea does have great merit for stabilising the albedo on Mars. For example Amazonia and Zaire forests stabilise the albedo on Earth (Gash and Shuttleworth, 1992).
4. Replace biogeochemical cycles. The Earth's biotas are pumps for the major bio-geochemical cycles (Schlesinger, 1991). From a longer term perspective, because Mars is believed to lack tectonic activity and therefore organisms such as microbes (Thomas, 1995) and plants (Fogg, 1995d) may play an essential role in the regulation of global nitrogen, carbon and other mineral cycles (McKay, 1982; Fogg; 1993; Thomas 1995). Whether purely biological cycles could replace bio-geochemical ones is a large problem facing "biological" planetary engineering (McKay, 1982; Fogg, 1995b; Thomas, 1995).
5. Hydrological functions. Plants play a part in hydrological cycles in addition to those discussed in (i), by controlling water runoff. Vegetation permits a slower and more regulated run-off, allowing water supplies to make a steadier and more substantive contribution to their ecosystems, instead of quickly running off into streams and rivers- possibly resulting in flood and drought regimes downstream. As the hydrosphere is gradually activated on Mars so these hydrological cycle becomes more important. It will be important to ensure that water is cycled by transpiration and rainfall.
6. Production of greenhouse gases. Microorganisms could be used to metabolise nitrate deposits to NH3. As discussed in section four, NH3 is a powerful greenhouse gas, so not only would this process contribute to the warming of the planet, but at low levels NH3 would be photochemically broken down into N2, a further greenhouse gas (H2O) and H2 (Kasting, 1982). (However, this pathway maybe undesirable as the H2 produced would probably be lost to space (Fox, 1993 and references therein). Another green house gas that could be produced by biological mechanisms is methane, CH4. Methane may have been a constituent of the Martian paleoatmosphere (Kasting, 1991). However, methane is rapidly photodissociated by UV-radiation, but an increase in ozone and efficient/abundant production of CH4 by biological organisms may partially mitigate this problem and lead to a net accumulation of CH4.
7. Biomass production and soil protection. On early Earth reduced organic material formed by fixation of carbon dioxide and carbonates was ultimately utilised by other organisms scouring the debris of destroyed cells. Thus pioneer microorganisms and subsequent generations will provide a pyramid of biomass for successive generations of organisms. (During initial planetary engineering the Martian surface will rarely be refreshed by rainfall and will be unable to retain moisture. Therefore hardy microorganisms which were able to utilise water vapour could be used to build up a "top soil").
The spread and settlement of vegetation protects soil cover. On Earth soil erosion is a major problem in many areas of the world, for example, it leads to declines in soil fertility. Although no soil is present on Mars with the growth of appropriate microorganisms gradually a biomass will begin to build up and the planting of trees, grasses and long rooted plants could, as on Earth, could be used to prevent large scale erosion (Figure 4).
8. Production of materials for colonists. Provided the relevant organisms can grow on Mars, these would include trees to provide wood for construction, food and medicines, antibiotics from fungi etc.
Figure 4. Photograph of plants on Mars. Once the oxygen level is around 20 mbar then plants can be introduced onto Mars. These will serve a number of functions including the production of more oxygen and stabilising geological features. A drainage channel caused by the recent flow of water can be observed in the background. In the foreground plants are growing and spreading toward the drainage channel preventing further erosion. (Photograph J. A. Hiscox and M. W. Parnell).
VII. The importance of biodiversity in planetary engineering
Also a key question is how many species are required to establish a stable ecosystem, either leading to Vitanova or Terranova? This concept is known as biodiversity and encompasses all life forms from the planetary species to populations of species together with their ecosystems and ecological processes. On Earth biodiversity plays two critical roles. (i) Biodiversity provides the biosphere with a medium for energy and material flows, which in turm provide ecosystems with their functional properties. (ii) It supports and creates ecosystem resilience, which will be absolutely crucial on Mars. Resilience can be defined as the ability of ecosystems to resist stresses and shocks, to absorb disturbance and to recover from disruptive change. All of these processes will be occurring during planetary engineering and indeed occur on Earth. The concept can be expressed more formally, it connotes an equilibrium-theory idea to the effect that ecosystems with their cybernetic mechanisms display homeostatic attributes that allow them to maintain function in the face of stress induced structural changes (Cairns and Pratt, 1995).
Biodiversity will be important during and after planetary engineering on Mars, one useful definition is of environmental/ecosystems services which reflect environmental functions and ecological processes and can be defined as any functional attributes of natural ecosystems that are demonstrably beneficial to mankind (Cairns and Pratt, 1995). Although, it is difficult to speculate on the composition of Martian ecosystems and to draw extrapolate from terrestrial ecosystems, on Earth the values provided by such systems include generating and maintaining soils, converting solar energy into plant tissue, sustaining hydrological cycles, running bio-geochemical cycles (including the elements carbon, nitrogen, phosphorus and sulphur), controlling the gaseous mixture of the atmosphere (which helps to determine climate-i.e. through the CO2/H2O greenhouse effect) and regulating weather and climate at both macro and micro-levels. Thus they basically include three forms of processing, namely of minerals, energy and water (Perrings, 1987).
Ecological services at first inspection often depend to appear not so much on biodiversity but on biomass. For example, when a patch of forest is replaced by a monoculture, the new vegetation can supply certain of the same ecological functions (and perhaps more efficiently), including photosynthesis, protection of soil cover, atmospheric processing and hydrological functions. However, on closer inspection biodiversity is extremely important, a monoculture may provide less cycling of nutrients and other soil nutrients and be more prone to disease.
VIII. Ramifications for the Martian environment of planetary engineering
During planetary engineering geological features will change, for example if the global temperature raises above 273 K then water in the form of ice will gradually begin to melt in the regolith. This has a number of consequences, for example, if rivers begin to form, the associated erosion may bring to the surface any buried organic material. Another important point to emphasise is that biology on Mars, at least during the initial stages of planetary engineering must always be used to add CO2/O2 /N2 /greenhouse gases to the atmosphere. It would be undesirable to reach a point where microorganisms initiate a global freezing because all of the CO2 has been re-sequestered as organic carbon.
The introduction of terrestrial microorganisms into the Martian environment, whether in greenhouses or for planetary engineering will obviously affect the search for any extinct, but especially extant Martian life. Before planetary engineering commences and during the initial stages the very surface of Mars will be sterilising for all forms of terrestrial life, whether genetically modified/adapted or not. However, if oasis of life do exist, then such enclaves may be over run by terrestrial organisms. Or perhaps if environmental conditions become more clement during planetary engineering such organisms will compete with terrestrial organisms. Therefore, a thorough search for "life" on Mars will perhaps be necessary before the wide spread introduction of terrestrial organisms.
IX. The dynamics of Martian environmental change versus the capabilities of a biological engine
For the "biological engine" to facilitate any planetary engineering effort certain environmental conditions discussed in section two will have to modified by non-biological means before organisms can be introduced. Most importantly a decrease in UV radiation and an increase in surface temperature above the freezing point of water. As discussed in section four, these conditions could both be accomplished by an increase in the atmospheric pressure. Undoubtedly the biological engine is very powerful, witness the conversion of the anaerobic environment on the early Earth to an aerobic biosphere via photosynthesis, a biological mechanism. Although, as Thomas (1995) points out, concrete data in the area of the biological engine is lacking and comparisons with terrestrial equivalents may be difficult to draw. Such predictions as to the effectiveness of a biological engine on Mars are hampered by four main factors; the composition, state and distribution of the volatile inventory and the performance of organisms under Martian conditions (Haynes, 1990). The forth coming Mars Pathfinder and Surveyor missions may provide some answers to the former three points and Marsjar simulations to the later.
X. Colonists/greenhouses and planetary engineering
Colonists and planetary engineering are very interrelated. The presence of colonists on the Martian surface has been proposed to be the main driving force behind the ultimate terraforming of Mars (Fogg, 1993). However, colonists and colonies on Mars will provide an integral role in assessing the feasibility of a planetary engineering scenario in a number of ways:
1. Simulating biological systems and planetary engineering in greenhouses. In order to become less dependent on supplies from Earth, such colonies are likely to utilize greenhouses for a number of purposes including food production and waste processing/recycling. Such greenhouses could be viewed as giant Marsjars as the atmosphere inside the vessels might, in part, resemble the atmosphere at some point during planetary engineering, such as the Terrariums proposed by the Obayashi Corporation (Ishikawa et al. 1990; 1993). For example, the spread of organisms throughout the Martian soil, biomass production and plant growth e.g. respiration versus photosynthesis in a high CO2 environment could be simulated and modeled.
The composition of a planetary engineered atmosphere has not been modeled in detail and colonist's greenhouses would probably contain more water than would be liberated by near term planetary engineering scenarios. One point to note is that H2O2 release by the Martian "top soil" may be toxic for organisms in the greenhouse (Zent and McKay, 1994). To overcome this problem efficient venting may be used, at least until the H2O2 production decreases to more tolerable levels. Alternatively, deeper soil deposits that do not contain oxides (Bullock et al. 1995) could be used.
2. Detailed volatile inventory. Colonists/explorers will be best able to assess the volatile inventory and distribution of materials essential for planetary engineering on Mars (Haynes, 1990; Haynes and McKay, 1992; Fogg, 1995c) and Antarctic research outposts may provide a useful model for this process (Andersen et al. 1990).
XI. From Vitanova to Terranova
Almost certainly, given near term technology, some form of ecopoiesis can be accomplished on Mars and Haynes (1990) suggested such a planet may be named Vitanova. Terraforming is more dependent on sufficient volatile inventory and is thus more uncertain than ecopoiesis. However, if terraforming is possible, i.e. to create Terranova (Haynes, 1990), then one of the main biological problems to be faced may be the environmental change from an anaerobic to an aerobic biosphere.
On the early Earth a stepwise improvement in anaerobic metabolism allowed cells to survive and multiply wherever they could find simple nutrients in solution. A similar process may occur during ecopoiesis. However, after several billion years on the early Earth, the accumulation of free oxygen in the atmosphere brought about a radical change in the biosphere. The anaerobes retreated to unaerated environments and newly evolved aerobes took over the surface. Bacteria that could survive the toxic effects of oxygen could also capitalize on the more efficient metabolism it supported. This luxury may not be afforded to organisms that have prospered during ecopoiesis. McKay et al. (1991b) calculated an oxygen biosphere may be obtained in 21,000 to 100,000 years via photosynthesis. This is considerably less time than the switch from an anaerobic to an aerobic biosphere in the history of the Earth. Therefore, anaerobic organisms may perish and ecosystems and the biosphere disrupted. The remains of these organisms may provide biomass for the organisms that remain or those that are to come. However, the consequences and benefits of such a decision to proceed with terraforming Vitanova must be carefully weighed with the risk of failure (Haynes, 1990).
In conclusion, in full agreement with McKay (1982), Haynes (1990) and Fogg (1995d) the relationship between biology and the planetary engineering of Mars can only be more accurately investigated when the volatile inventory, chemical state and geological distribution is determined. Also, extensive analysis of the performance of GEMOs and terrestrial microorganisms using Marsjars will be required. However, given the suitable abundance of such volatiles and moderate advances in technology, there is no biological reason why the goal of at least Vitanova cannot be realized.
I wish to extend my thanks to the following people for providing both valuable discussions, suggestions and advice: Martyn Fogg, Imre Friedmann, Bob Haynes, Lee Lindner, Chris McKay and Tom Meyer.
| Roswell or Bust - Part 20 of 43 ||Â© 2008 by Henry Melton|
The Cottonwood Motel. Joe nodded. It was a nice place, a collection of small two-story wood-frame buildings circling a separate office building. It was a shady place, probably because the trees were a lot older and larger than when the property was put together. Two or three dozen units altogether, depending on whether there were some entrances on the back side.
Interestingly, there was a âNo Vacancyâ sign, here in the middle of the day, and few cars in the parking lot.
He hesitated, then walked up to the office. There was a large Harley-Davidson motorcycle, resplendent in chrome, parked inside the office.
The door opened at his touch.
âYes, can I help you?â The lady at the desk asked.
Joe felt very strange to be on the receiving end of that phrase.
âPardon me. I was just looking over your place.â
She was attentive and older than his mother. He flushed.
âIâm sorry, I was just in town and this place attracted my attention. Iâm in the motel business myself.â
He strode up to her desk, âYes. Iâm Joe Ferris. I live in Las Vegas, New Mexico. My family owns the Railroad Motel there.â He shrugged, âI mind the office, do maid service, and general errands.â
âIâm Alice North. Iâm the owner here. Nice to meet you.â
He succumbed to curiosity. âWhy no vacancies in the middle of the day?â
âThings changed. Thereâs a building boom here in town, mainly due to the oil business. Currently all my rooms are on monthly contract to workers here.â
âThatâs interesting.â He glanced around the office. It was pleasant. Not as big as his, but designed to make the guests comfortable.
âCould I sit here for a while? Iâm waiting for someone.â
She gestured to the chair. âWhat are you doing in Wyoming?â
âThatâs a long story.â He sat down where he could keep watch on the traffic. Maybe sheâd never come back, but he had to be ready if she did.
Blake reported, âThe tower at Rock Springs Airport reports that Valet is preparing for take-off.â
âCan they be stopped?â
âNot on our say-so.â
âHow far are we out?â
âThirty minutes yet.â
Carl fumed. They had to land BellBoy to refuel. There was no way they could chase the other plane, nor force it to land.
âGet them on the radio.â
Blake looked at him to confirm, then turned the frequency to 122.75. âValet, this is BellBoy. Please respond.â
It was a couple of minutes before there was an answer.
Blake handed over the headset to his boss.
He pressed the push-to-talk button. âThis is Carl Morris.â
There was another delay, and then a familiar voice came over the earphones.
âI thought it would be you, Oscar. Although I canât understand what youâre doing here.â
He released the talk button. Heâd have to be careful. This was radio. Anyone could listen in.
âNo, I guess you wouldnât. Having fun flying around wasting the companyâs fuel? I thought you were Mr. Economize.â
âBetter than attempting to destroy everything in a bid for power. Turn back. Weâll be at Rock Springs shortly. Letâs talk this thing out face to face before something happens that canât be un-done.â
âSorry, Sonny. I donât know what you think youâre doing, and honestly I donât care, but Iâm racing the clock.â
âThereâs nothing you should be doing, Whitfield. I thought I was being kind putting you on retirement. But let me make it clear. Your department is SHUT DOWN. You are fired. Iâve already sent out the code. You and all your crew of traitors are banned from company activities.â
âTraitors, eh? Maybe traitors to you and your new generation, bean counter, shortsighted yes-men! Although why I should have any loyalty to someone who would sell out his own father, I donât know.â
Carl clenched his teeth. Whitfieldâs battle to reactivate the exobiology research group had been loud and angry on both sides. His claims for new breakthroughs in medicine were unsubstantiated and frankly pathetic attempts to keep his department alive long after the Trustâs dwindling resources couldnât support it. And Whitfieldâs claim that budget cuts would condemn Luke Morris to death had been the last straw. Carl wouldnât put up with the dirty insider politics.
But Whitfield wasnât finished.
âYouâve banned me, Mr. Junior Executive? How are you going to enforce that?â
The signal was fading. By now, the planes were separating at many hundreds of miles per hour, and they were using the aircraft version of a party line. Other conversations between pilots were breaking up the signal, and what was worse, the others were listening in to their private fight.
Carl didnât bother to answer the jab. He signaled to Blake, who switched the radio off the air-to-air channel and took the headset back.
Better to stop talking now. Theyâd had this argument before, behind closed doors, which is where it belonged.
The problem was that Whitfield had a point. He had no way to enforce his ban. The Trust was built on loyalty. His father and his number one, Whitfield, had built the organization carefully, adding people only after long and careful screening.
When you were protecting the human race from the disruption of alien contact, and at the same time doing your best to put a good face before your alien Guests, you needed good people who took their duty seriously.
He couldnât go to the police, not even for something as blatant as the theft of an airplane.
They began their descent into the Rock Springs - Sweetwater County Airport.
âBlake, did we get a direction finder on Valet?â
âYes, the plane did some weaving when you were talking, but I still think theyâre on route back to Roswell.â
Whitfield had been arrogant, confident. Heâd gotten what he came to Rock Springs for.
âGet us refueled and turned around as fast as possible.â He needed to be ready for the next twist in Whitfieldâs power grab.
âYou mean youâre here alone?â
Joe looked sheepish. âYes, Maâam. My ride... left.â
After a nice long talk, where Alice told him all about the town, the motorcycle in the office, and the motel business in Rock Springs, sheâd finally uncovered why he was sitting in her chair. He had nowhere else to go.
She was concerned. âHave you called your family?â
Joe rubbed his nose, âAh, not yet. She might come back for me.â
âJoe, your girl friend dumped you a thousand miles from home. You have to call your family.â
He shook his head, âNot yet. Itâs not like you think. Weâre not like âromantically involvedâ or anything. Itâs not even her that asked me to come. Her dad asked.
âYou might even know him. A regular. About once a week. John Smith is his name. Drives a silver Lexus SUV. He had an accident. The carâs all scraped up, but it was a nice one. Ring any bells?â
Mrs. North shook her head. âWeâve had several John Smithâs, of course, but I donât remember the car. Not that it means anything. No overnight business lately, remember.
âJoe, you can use my phone. Your parents need to know youâre okay.â
âItâs not that. Iâve got phone money. Iâm just not ready to give up on her yet. Really. Sheâs got her own reasons for how she does things.â
Joe looked toward the street again.
âIf I call home, Dad will make a fuss and try to send money for a bus ticket or something. If I can just wait it out, and she comes back, then weâll be able to drive back and itâll be okay.â
âJoe! You think youâre old enough....â
He jumped to his feet. âHey! There she is!â He dashed out the door.
Coming down the street at a snailâs pace was the travel-worn Lexus. There was a squeal as the tire scraped up against the curb. The vehicle jerked and the tire jumped up on the concrete. The car behind it honked and passed by.
Joe ran out into the street, waving. He couldnât see inside, due to the tinted glass, but raced around and grabbed the passenger side door. It wasnât locked.
Across the street, he noticed that Alice North had come to the door to watch.
He jumped in. âJudith, where....â
It wasnât Judith in the driverâs seat.
Joe stared at the large dark eyes of a three-foot tall alien. A Roswell Gray in a dusty polo shirt and baggy shorts was driving the car. With both hands, it shifted the car into park. The car lurched to a stop in the middle of the street.
A thin voice like a parrotâs croaked, âHelp.â
Joe just froze, staring. The alien climbed up, standing on the seat and pointed long thin fingers to the back.
Judith was sprawled out, sleeping, in the back seat. Sheâd slid into an uncomfortable position.
âHelp,â the alien pointed to her.
âJudith?â Joe reached over and shook her. She was warm, and he could see her breathe, but she was unconscious.
âI need a talkie.â
A lot of pieces came together in one secondâdecades old secret organizations, mysterious men dressed in black, strange cargo that must not be seen, Roswell, and most importantlyâa gadget that translated between different people, even different species. It was like a bad movie come to life.
The alien watched him. âHelp.â
âIs... is Judith okay?â
The alien blinked. He pointed to the map screen. A line traced the path of the car. The alien moved its finger from their current position north to the place where the car had been. âHelp.â
Joe checked Judith again, but there was nothing he could do.
Out the window, he could see Alice North walking his way.
âGet in the back seat.â He said, pointing. Hesitantly, the alien did so.
Joe climbed over the center console and put the car into drive. He pushed the window button. He waved and smiled to Alice, but drove off before she could reach them.
He closed the window and glanced at the rear. The alien was struggling to get Judith back upright in the seat.
Honk. Joe snapped his attention back to the road.
He glanced at the map and turned to the north. The first empty parking lot he could find, he pulled in and stopped.
The alien looked at him expectantly. He was sitting in the seat, his seatbelt properly strapped in place.
Judithâs hair was a mess and obscured her face, but she had been strapped in place as well. Sheâll have a neck cramp when she wakes up.
If she woke up.
âWho are you?â He didnât know what else to say. Could the alien even talk, other than to say the one word, âHelpâ.
With an exaggerated gesture, thin fingers pointed at its chest. âBob Four.â It was still parrot-like, but clearly recognizable.
Joe nodded, feeling a little on familiar ground. âMy name is Joe Ferris. Nice to meet you.â
Bob Four tapped the side of his head, where there should have been an ear, and tried to repeat his name. What came out was like, âOris.â
Joe pointed to Judith. âWhatâs wrong with her?â
Bob tapped his head. Stiffly, he shook his head. âNo.â
What do I do now?
The alien Bob seemed to be waiting for him.
Judith was unconscious, but Bobâs reaction was reassuring. Heâd made sure she was safe, but once he did that, there was no sign of concern.
Of course, he couldnât read an alienâs body language, but if she were in danger, wouldnât he do something?
Things Judith had said now made more sense. The cargo had to have been something important for the alien. She had been concerned. It had been something more than just a duty. She cared about the alien. Hopefully, the alien cared about her too.
Bob pointed past his head. Joe looked. The navigation map.
âCome up here and show me.â Joe gestured an invitation. How much English did he know? He couldnât say many words, but he seemed to understand more.
Bob Four scrambled up into the front seat, his long arms and legs giving him motion more like a large spider than a monkey.
Bob made sure he had his attention, and then slowly and carefully traced the line from their current location to that destination a few miles to the north. Bob tapped the gearshift lever.
âOkay. Weâll go there.â
Bob scrambled back to his seat and clicked himself in.
Joe circled back to the route Judith had taken north, and Bob had retraced.
If he drove her into town, why does he want to go back now? He wished hard for the talkie.
Driving with the map, he set the scale so he could see every street and every turn. At close zoom, he could see that there were two traces, and he had no doubt which was Bobâs. One was direct. The other wove all over the place, taking side roads, backtracking in illogical ways.
The guy was only three feet tall. How could he have kept his feet on the pedals and looked out the windshield at the same time? Maybe he hadnât. The thought gave Joe the shivers.
Driving, his mind was a whirlwind of speculation. The Roswell story was true? Heâd never have believed it. Tall tales were a staple of the Southwest, and when he heard a new one, he could usually tell when one was based on history and when it was wishful thinking by a tourist bureau. Dad had even said how much he wished they had something like Roswellâs UFO Museum to draw people to the town.
Guests had talked to him about Roswell plenty of times. The town had all the markings of a place that knew how to milk a gimmick. The museum there was on his personal to-do list.
Had the government been able to keep a lid on this all these years by making it look ridiculous?
That didnât feel right. How could the government keep it a secret? There were too many people whoâd blow the whistle.
Iâve even got the urge to get out of the car and run around screaming, myself.
He moved his head and saw the mop of Judithâs hair. âSecrecy is a big part of our family job,â Sheâd said. âEven if Dad hadnât made me promise to keep this delivery run a secret, Iâve grown up with secrets.â
Was that how they did itâpeople growing up with the secret, never letting outsiders know anything?
âOris.â Bob pointed.
Joe nodded. The track on the map took a sharp turn. Joe followed the way onto Bekker Ranch. What in the world would they find here?