Excursion Chapter 1: The Origin Of Life
Outline of the Pandas Chapter
Scientists today propose two general explanations:
- The natural origin of life on earth from nonliving matter according to chemical laws.
- Origin of life in outer space and subsequent colonization of earth (see Shapiro, 1986; Hoyle and Wickramasinghe, 1981).
Origin by an intelligent designer (creator) is tenaciously held by certain religious groups who, for political reasons, pretend that it is a scientific explanation. Everything about the creation is claimed to be supernatural (Morris, 1974, pp. 11-12) which means the creator and its activities is beyond human understanding (Bassinger and Bassinger, 1978). Hence this idea is not an explanation (let alone a scientific one) but a reaffirmation of a religious miracle. Any scientists that espouse this idea do it for religious reasons (i.e. the Bible says so) and not because of any scientific evidence for it. They have admitted this in court proceedings (Lewin, 1982a ). In fact, creationists have stated that it is impossible to know anything scientific about the origin of life (Morris, 1963, p. 56; Morris, 1967, p. 19, 59-60; Morris, 1972, p. 16; Morris, 1974, p. 4; Gish, 1973, p. 8).
Spontaneous Generation — Science Does A "Double Take"
Spontaneous generation as "a process of self-organization without outside intelligence" (Pandas, p. 41, 43) is a modern-day creationist-concocted definition. For many centuries, spontaneous generation was the more-or-less instantaneous appearance of complex organisms. For many Christians, it was the visible, present-day creation of organisms by God (the creator, intelligent designer, etc.).
Spontaneous generation is a belief that has persisted throughout history. People believed that spontaneous generation came about as the result of secondary supernatural creative acts of God. This belief was incorporated into Christian theology and, beginning in the 4th century A.D., appears in the writings of all the great Christian theologians, including Basil, Gregory, Augustine, Bede, Isidore, Lombard and Aquinas (White, 1960, vol. 1, pp. 42, 46, 52-56; Oparin, 1953, chapter 1). Thus it is really the creationists who, for centuries, believed in spontaneous generation.
Although Pasteur proved that spontaneous generation of present-day organisms from inorganic matter did not occur, "he nevertheless believed in the possibility of abiogenesis and attempted to produce life artificially in the laboratory." This belief "stemmed from his conception of an 'asymmetric force,' the intervention of which he considered essential to the production of asymmetric molecules and, hence, of life." Pasteur's main opponent in the spontaneous generation controversy, Pouchet, was a creationist who believed that spontaneous generation was part of God's grand design, and a vitalist—only organic chemicals, that still retained some "force plastique" could give rise to organisms (Farley, 1977, pp. 108-119 for Pasteur's various views on the matter; pp. 114-115, 117-118 in particular for asymmetric forces; pp. 98, 116 for Pouchet).
In Pasteur's time, scientists had a variety of opinions about spontaneous generation; many of the creationist catastrophist geologists accepted it while many evolutionists didn't. The last sentence of Darwin's Origin of Species reads:
"There is grandeur in this view of life, with its several powers, having been originally breathed by the Creator into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being evolved."
This quote clearly demonstrates that the natural origin of life and evolution (that living creatures may exhibit "descent with modification") are two separate notions. The fact that there is much to learn about how the first living creatures originated has little to do with the truth or falsity of evolution. Thus an intelligent designer could have made the first forms and then they evolved. But, as I have previously discussed, that doesn't explain anything.
A Theory Is Born
The modern scientific hypothesis that living creatures arose by a step-wise series of chemical interactions is so fundamentally different from the old idea of spontaneous generation that the British biochemist Pirie suggested that it be given a different name: biopoesis (Pirie, 1954, p. 43; Gaffron, 1960, p. 40).
Oparin's hypothesis is described in terms of seven assumptions. These assumptions are formulated by the Pandas authors, not Oparin, and several of them are superfluous or incorrect (3, 4, 6, 7) as will be discussed below. Although these assumptions state that various mechanisms "originated gradually" (presumably in stages), Pandas later criticizes the hypothesis (see section on problems with proteinoid microspheres) by discussing the unlikelihood that all the mechanisms arose instantaneously in their full complexity! Oparin did further experiments with various types of coacervates and discovered simple systems that could reproduce, carry out simple metabolic functions, mimic the electron-transport system or mimic photosynthesis (Dickerson, 1978).
What Experimental Studies Of The Origin Of Life Can Tell Us
The Miller-Urey Experiments
Problems With The Assumptions Of The Oparin Hypothesis
Contrary to the assertion of Pandas, the geological evidence supports the fact that free oxygen was rare or not present in the atmosphere of the early earth. Sedimentary deposits older than two billion years contain no ferric oxides or other highly oxidized minerals. In fact, the evidence seems to indicate that the earth's oxygen atmosphere was produced by the activities of prokaryote photosynthetic organisms (Day, W. 1979, p. 74; Schopf, 1978, p. 60). Thaxton et al (1984, chapter 5) suggest that oxygen was present in the atmosphere at an earlier time based on the age of early prokaryote fossils judged to be photosynthetic. This would still put oxygen in the atmosphere at a time after the prebiotic chemical evolution phase of the origin of life. There is controversy about the exact nature of the early reducing atmosphere but a Urey-Miller type of experiment works just as well in atmospheres of various mixtures of gases—hydrogen, nitrogen, carbon monoxide and carbon dioxide—as long as free oxygen is not present (Dyson, 1985).
Pandas insists that "traps" did not exist on the primitive earth, but this is not true. For example, thunderstorms and lightning can occur at night. Amino acids and other monomers would be carried to the earth's surface in the rain where they might accumulate in shallow pools. Those under rocks, or in the interstitial spaces of the gravel, sandy or mud bottoms of the pools would be shielded from the ultraviolet rays of the next day. Also, only a tiny portions of the sun's output is at wavelengths shorter than 2,000 Angstrom units where it could be absorbed by such compounds as CH4, H2O and NH3. Possibly H2S, activated by the longer UV wavelengths, instituted synthesis reactions among these small molecules, the products then being washed into the oceans or freshwater bodies by rain (Fox and Dose, 1977, p. 78; Orgel, 1973, pp. 116-117). There, the more complex compounds would have been protected from the longer UV wavelengths. The primitive ocean would have been rendered even more opaque to UV by the layer of organic compounds near the surface (Miller and Orgel, 1974, p. 59). Recently it has been suggested that other sulphur compounds high in the atmosphere might have functioned similarly to today's ozone layer (Science News, 1988; 134(26,27):423). Ultraviolet light was not necessarily the major energy source for the prebiotic synthesis of organic compounds.
One remarkable fact about Miller-Urey type experiments is that, out of the thousands of possible compounds they could have produced, they produced relatively few substances and most of these are important compounds, amino acids, etc. found in all living organisms! And they are formed with surprising ease under prebiotic conditions (Orgel, 1973, pp.127-130; Miller and Orgel, 1974, p. 84; Fox and Dose, 1977, pp. 86, 141). Pandas' vision of tens of thousands of varieties of chemicals tying up useful chemicals in cross-reactions is incorrect. The large yields of "non-biological goo" mentioned on p. 5 has never been analysed, although there is evidence that it might be proteinaceous (Life Signs, 1984). Polymerization of the simple monomers would be facilitated by concentration caused by evaporation or freezing of the water or by the adsorption of the organic materials on clays. Fox (see below) polymerized mixtures of amino acids by drying and heating them (Dickerson, 1978).
Contrary to Pandas' assertion about the prevalence of "clay deposits of the time", early Precambrian sediments, unchanged by heating and metamorphosis, are rare. Many of those that do exist already contain microfossils similar to protein microspheres, representing early prokaryote organisms. The organic materials in these rocks have properties indicating a biological origin (Fox and Dose, 1977, pp. 292 fol.; Day, 1979, pp. 80 fol.). Many simple organic compounds are abundant in interstellar space and in comets. Organic material including racemic mixtures of amino acids (Fox and Dose, 1977, chapter 11; Miller and Orgel, 1974, chapter 15) and lipid-like organics able to self-assemble into membranes (Raloff, 1986) have been found in meteorites, indicating that prebiotic syntheses of organic monomers can and did occur in nature.
There are no biochemical reasons that the primordial living forms could not have been mixtures of the left- and right-handed amino acid forms, and that later, one form was selected by catalytic action of inorganic surface catalysts (certain clays) or biological enzymes (Dickerson, 1978, p. 36). Proteins can be made from racemic mixtures. Gaffron (1960, pp. 66, 72) discusses why forms using only one isomeric form of amino acids would be selected over those utilizing mixtures. Right-handed amino acids do occur today in certain bacterial proteins (Downes, 1962). Several right-handed amino acids (tryptophane, phenylalanine, methionine, histidine) will support growth in rats (West and Todd, 1951, p. 1151).
The results of hundreds of research projects over the last 30 years by scientists working in the field of protobiochemistry have established the following facts. Under very simple, straightforward circumstances, that must have been a common natural occurrence in the history of the earth, amino acids and nucleic acids do form from simpler common chemical compounds. The amino acids polymerize into peptides that in turn aggregate into larger, protein microspheres (protocell-like structures). All these steps occur by definite, deterministic (non-random) chemical processes (Fox, 1981b). Intensive study of the properties of the protein microspheres by many different protobiochemists have revealed that, while they are definitely not full-blown modern living cells, they exhibit many of the properties of living cells, including membrane structures with semipermeable properties, enzymatic activity associated with various metabolic reactions, synthesis of protein linkages as well as nucleic acid linkages, growth, excitability (neuro-electric phenomena similar to those in nerve cells), motility and conjugation (Fox, 1981a; 1984; Peterson, 1985).
Problems With The Proteinoid Microspheres
We have already dealt with Pandas' assertion about many cross-reactions in dealing with their discussion of Oparin's assumption no. 3. One can form proteinoids very easily (high school students have done it in science fair projects). It is accomplished in the lab with heat and they are not destroyed. Only gentle heating is required. Furthermore, once they coalesce into microspheres they are very stable. Creationist criticisms of microspheres are dealt with by Fox (1984).
In judging the impossibility of the origin of a first protocell by natural means, Pandas consistently assumes that it must have the full complexity of a modern cell. This is about as intelligent as an aeronautical engineer insisting that a functional airplane must have the technological sophistication and complexity of a modern jumbo jet, thereby refuting the historical assertion that the first airplane was constructed in a bicycle shop. Certainly the first protocells were as simple and primitive relative to modern day cells as the Wright flyer was to a Boeing 747.
The present-day complex mechanism of protein synthesis was probably preceded by something much simpler. Some researchers think that the earliest protocells used RNA, because nucleic acid bases can polymerize into nucleic acids which reproduce themselves without the aid of the complicated enzyme systems found in modern cells (Beibricher, 1983; Eigen et al, 1981; Lewin, 1982b). Some RNAs even display catalytic properties (Cech, 1986). By further evolution, RNA molecules encoding protein enzymes aiding RNA reproduction could be added. The chemist D. H. White has shown theoretically that the simplest such self-replicating system or "autogen" consists of two RNA fragments, each encoding a simple peptide catalyst, one to assist in RNA replication and the other to drive the translation of RNA information into the peptides. The RNA chains could have been as short as 10 units (Garmon, 1981; Trachtman, 1984).
Other researchers postulate, because of the ease with which amino acids and peptides can be produced by abiotic means, that the first protocells contains protein only (like Fox's protein microspheres) and only acquired nucleic acids later for more efficient information storage and reproduction (Dyson, 1985). Could protocells based on proteins only have reproduced themselves by some autocatalytic process? There are some bacterial products that are noncoded peptides (Day, 1979, p. 369). Also there are infectious "virus-like" particles called prions, that are apparently devoid of nucleic acid (Dyson, 1984, p. 26 fol.; Prusiner, 1982; Prusiner, 1984). Nucleic acid particles may have entered into symbiosis with the protein protocells and subsequently specialized in information storage and protein synthesis—much like mitochondria and chloroplasts are thought to originated as symbiotic prokaryote organisms, eventually giving rise to the eukaryote cell (Margulis, 1974; Avers, 1989, pp. 115 fol.)
Enzymes could very well have evolved gradually and in stages. The earliest catalysts could have been metal ions (which function as cofactors for many modern enzymes, hydrous iron and manganese minerals (Science News 131(10): 152. March 7, 1987) or clay minerals that absorb organic materials on their surfaces. The enzyme catalase that catalyzes the decomposition of hydrogen peroxide to water and oxygen consists of a polypeptide attached to a heme (porphyrin) group that in turn contains ferric ion. The bare aqueous iron ion can catalyze the reaction but very inefficiently. Combining the iron ion with a heme group increases the catalytic ability by a thousandfold. Finally adding the polypeptide increases the catalytic function even further (Calvin, 1975). As we shall see in chapter 6 with respect to cytochrome c, there are many polypeptide sequences with the same functional properties and probably even more with similar properties. Thus any one of many polypeptides might have increased catalase activity; this being increased by natural selection of the more efficient variants during subsequent evolution. Waiting for a rare, unique polypeptide sequence to occur by chance is unnecessary. Even among present-day organisms, genetic variations of many enzymes are known (Koehn and Eanes, 1978).
The earliest cells were probably metabolically simple, getting all their necessary compounds from the prebiotic soup. As the supply of say, compound F dwindles, any cell with the capacity to synthesize it from a simpler precursor, E would have a selective advantage. When E becomes scarce, evolution of a new enzyme might allow some cells to use precursor D to make E and then F. By extension of such sequences, the step-wise development of more complex metabolism could have occurred (Avers, 1989, p. 82 fol.; Horowitz, 1945; Orgel, 1973, p. 174; Miller and Orgel, 1973, chapter 14). The evolution of new enzymes and enzymatic functions by mutation and natural selection has been demonstrated in bacterial cultures (Hall, 1982; Mortlock, 1982).
Cell membranes form spontaneously (self-assemble) like liquid crystals as a result of the chemical properties of their phospholipid molecules (Ambrose, 1982, p. 33). Such membranes will naturally absorb organic materials to form "protocells" (Trachtman, 1984). The biopoesis hypothesis asserts that living organization arose gradually in stages from very simple beginnings. It does not assert that modern-type cells with their great complexity arose instantaneously and spontaneously. That is what the intelligent design proponents (creationists) assert and they have no idea at all as to how it was accomplished! In fact they assert that it was a supernatural event forever beyond human understanding.
The key feature of photosynthesis is the photochemical splitting of water as a source of chemical energy to synthesize carbon compounds. Very simple coacervate drops containing chlorophyll can accomplish this and drive simple reducing reactions (Dickerson, 1978). Pandas' assertion that the process could not have developed by natural means is unjustified.
Scientific Evidence For The Intelligent Design Of Life
Pandas claims that there is a reasonable explanation for life's origin that has scientific support. It can't be intelligent design! We have already mentioned that this supernatural belief denies the possibility of understanding life's origin.
The embryogenesis of an organism is only vaguely like the process of building a house. The important and fundamental differences will be discussed below.
What scientific evidence exists to support intelligent design? The only direct evidence for intelligent design, spontaneous generation, has been disproved! Pandas claims that only intelligent design can yield amino acids of only one stereo isomeric form. I have already explained how that might have occurred naturally (see section above on the problems with the assumptions of the Oparin hypothesis).
An Analogy (And Problems With Intelligent Design)
Pandas doesn't discuss any weaknesses or problems associated with the intelligent design hypothesis (they obviously consider it perfect), so I will point out a few basic ones:
Their case depends on a questionable and logically faulty analogy. The analogy between organisms and manufactured articles is quite weak. Some manufactured devices do exhibit complexity, but they also display many fundamental differences from organisms that will be explored below. If the pickup truck left at the native village has, say, a sheep dog sitting in the cab—an animal we shall assume they never saw before—what would they conclude? That this animal was manufactured in some kind of celestial factory in the same way that they fabricate bows and arrows? Hardly. They would assume that it had been born of some appropriate parents! That is the proper conclusion following from an application of the "principle of uniformity." All organisms come from preexisting life. Pandas spent some pages disproving the possible exception (i.e. spontaneous generation). It is puzzling that the Pandas' authors should resort to David Hume's law of uniformity. Hume, in his book Dialogues Concerning Natural Religion, shows that the "Argument from Design," which is what Pandas is using here, is illogical and contrived. Norman Kemp Smith, late professor of Metaphysics at Edinburgh, in his introduction to Hume, explicitly points out the organisms are not like designed, manufactured objects (Hume, 1947, p. 102). Kaufmann gives his own brief version of Hume's argument (Kaufmann, 1958, section 45, pp. 114-115). Even Augros and Stanciu (1987), a book recommended by Pandas, makes this point (Augros and Stanciu, 1987, chapter 2). See the supplement: The Illogical Argument From Design, for further details.
Pandas claims that living cells are more like pickup trucks that microspheres! An internal combustion engine may not come into existence because of the physics of the metals from which it is made. But cell membranes do come into existence because of the chemical properties of the phospholipid molecules of which they are made. They are self-assembling, as are protein microspheres. Molecular self-assembly makes possible the chemical industry. Chemical are not manufactured by having workers screwing or bolting atoms together on an assembly line. No, the appropriate reactants are mixed in a vat under the appropriate conditions of concentration, temperature, pH, etc. and they assemble themselves into the product! There is no way DuPont can manufacture a chemical substance unless the atoms can be cajoled to form it on their own. The other structures of organisms come into being in similar fashion. Embryologists can watch closely the development of a frog or chick embryo. Structures form without the aid of artisans forming and assembling the parts. In this fundamental way organisms and protein microspheres are alike—their structures comes from the properties of the molecules of which they are made—and pickup trucks are quite different.
The nature of the information in DNA is not in the form of blueprints or specifications, but is more of the nature of a recipe (Dawkins, 1986, pp. 295 fol.). In development, appropriate substances are produced at the right time and these produce structures through their self-assembly. The genetic information can reproduce itself. In sexual reproduction, this information is reorganized into new forms. Note that in sexually reproducing species, no two individuals are identical (unless they are "twins" coming from the division of a single zygote—which is a form of asexual reproduction.) Manufactured items are all alike. You can't mix up the plans for two different automobiles and build a new car from them without a lot of engineers and mechanics making modifications.
The above considerations illustrate another fundamental difference between the reproduction of organisms and the production of manufactured items. The parts of the latter are formed independently of one another and only fit together on an assembly line because they were built to the specifications of a plan. The parts of an organism are formed during embryogenesis, in situ, where they can constantly interact with one another and adjust their sizes and shapes so that a functional organism results, even if that particular combination of genes produced at random from those of the two parents has never occurred before. Clearly intelligent activity is not needed in embryogenesis. Besides reproduction, organisms can repair themselves and grow and change by evolution. Even Pandas admits the reality of microevolution.
Given these facts and the principle of uniformity, it follows much more logically that the succession of fossil forms found in the sedimentary strata are descended from one another, rather than continually created anew by some kind of spontaneous generation (creation by an external intelligence) which has been proven not to occur in the present!
Modern ideas about the gradual step-by-step evolution of living things from nonliving components (which is not spontaneous generation) may not yet have come anywhere near answering all our questions about the process, but at least they involve hypotheses that can be tested and investigated by scientific means. A great deal of biogeochemical knowledge has resulted. (There is a journal, Origins of Life, devoted to publication of the results of biopoesis research.) None of this research has indicated that biopoesis is impossible. On the contrary, much of it has revealed how various necessary aspects of biopoesis might have readily come about along with tantalizing hints as to how protein synthesis and the genetic code might have arose! Also, such scientific research may have unexpected ramifications. The discovery that RNA could act as an enzyme was not only of great interest to scientists working on the origin of life but it led to the development of RNA enzymes to fight viral diseases (Radetsky, 1990). On the other hand, the intelligent design hypothesis has been around for several centuries and nothing has come of it! Until intelligent design proponents flesh out their vague, supernatural belief with testable ideas as to the nature of the designer(s) and how it (they) work, there will not and cannot be any scientific research along that line.
Pandas points out that Shapiro, 1986 (see Suggested Reading/Resources) gives a good critique of chemical evolution. He also provides a devastating critique of creationism. Good modern summaries of biopoesis research are given by Avers (1989), Kutter (1987) and Mason (1991). Older references are Day (1979), Orgel (1973), Miller and Orgel (1974). A more technical and biochemical review is given by Fox and Dose (1977).
Ambrose, E. J. 1982. The Nature and Origin of the Biological World. Ellis Horwood, Limited.
Augros, R. and G. Stanciu. 1987. The New Biology: Discovering the Wisdom in Nature. New Science Library of Shambhala Publications Inc.
Avers, C. J. 1989. Process and Pattern in Evolution. Oxford University Press.
Bassinger, D. and R. Bassinger. 1978. Science and the concept of miracle. Journal of the American Scientific Affiliation 30(4): 164-168.
Biebricher, C. K. 1983. Darwinian selection of self-replicating RNA molecules. Evolutionary Biology. 16:1-52.
Calvin, M. 1975. Chemical Evolution. American Scientist 63(2): 169-177 (March/April)
Cech, T. R. 1986. RNA as an Enzyme. Scientific American 255(5): 64-75 (November).
Dawkins, R. 1986. The Blind Watchmaker. W. W. Norton and Company
Day, W. 1979. Genesis on Planet Earth. House of Talos Publishers.
Dickerson, R. E. 1978. Chemical Evolution and the Origin of Life. Scientific American 239(3): 31-46.
Downes, H. R. 1962. The Chemistry of Living Cells. 2nd Edition. Harper and Row.
Dyson, F. 1985. Origins of life. Cambridge University Press
Eigen, M., W. Gardiner, P. Schuster and R. Winkler-Oswatitsch. 1981. The Origin of Genetic Information. Scientific American 244(4):88-119 (April).
Farley, J. 1977. The Spontaneous Generation Controversy from Descartes to Oparin. Johns Hopkins Univ. Press.
Fox, S. W. 1981a. From Inanimate Matter to Living Systems. American Biology Teacher 43(3): 127-135, 140 (March).
Fox, S. W. 1981b. Creationism, the Random Hypothesis and Experiments. Science 213: 290 (17 July).
Fox, S. W. 1984. Creationism and evolutionary protobiogenesis. In: Montagu, A. (Ed.) Science and Creationism. Oxford Univ. Press. pp. 194-239.
Fox, S. W. and K. Dose. 1977. Molecular Evolution and the Origin of Life. Revised Edition. Marcel Dekker Inc.
Gaffron, H. 1960. The Origin of Life. In: Tax, S. Evolution After Darwin. Volume 1. The Evolution of Life: its origin, history and future. University of Chicago Press. pp. 39-84.
Garmon, L. 1981. As It Was In The Beginning. Science News 119(5):72-74.
Gish, D. T. 1973. Evolution The Fossils Say NO! 2nd Edition. Creation-Life Publishers.
Hall, B. G. 1982. Evolution on a Petri Dish: The Evolved Beta-Galactosidase System as a Model for Studying Acquisitive Evolution in the Laboratory. Evolutionary Biology 15: 85-150.
Horowitz, N. H. 1945. On the evolution of biochemical syntheses. Proceedings of the National Academy of Sciences 31(6): 153-155.
Hoyle, F. and N. C. Wickramasinghe. 1981. Evolution from Space. Simon and Schuster.
Hume, D. 1947. Dialogues Concerning Natural Religion. Thomas Nelson and Sons, Ltd. (First printed in 1779. This edition edited with an introduction by N. K. Smith, late Prof. of Logic and Metaphysics, the University of Edinburgh)
Kaufmann, 1958. Critique of Religion and Philosophy. Harper and Bros.
Koehn, R. K. and W. F. Eanes. 1978. Molecular Structure and Protein Variation within and among Populations. Evolutionary Biology 11: 39-103.
Kutter, G. S. 1987. The Universe and Life: Origins and Evolution. Jones and Bartlett.
Lewin, R. 1982a. Where is the Science in Creation Science? Science 215: 142-146 (8 January)
Lewin, R. 1982b. RNA can be a catalyst. Science 218:872-874 (26 November).
Life Signs. 1984 (A note on the origin of proteins). Discover 5(6):11 (June).
Margulis, L. 1974. Five-Kingdom Classification and the Origin and Evolution of Cells. Evolutionary Biology 7: 45-78.
Mason, S. F. 1991. Chemical Evolution: Origins of the Elements, Molecules and Living Systems. Clarendon Press.
Miller, S. L. and L. E. Orgel. 1974. The Origins of Life on the Earth. Prentice-Hall, Inc.
Morris, H. M. 1963. The Twilight of Evolution. The Craig Press.
Morris, H. M. 1967. Evolution and the Modern Christian. The Presbyterian and Reformed Publishing Co.
Morris, H. M. 1972.The Remarkable Birth of Planet Earth. Institute for Creation Research.
Morris, H. M. (Editor). 1974. Scientific Creationism. Creation-Life Publishers.
Mortlock, R. P. 1982. Regulatory Mutations and the Development of New Metabolic Pathways by Bacteria. Evolutionary Biology 14: 205-268.
Oparin, A. I. 1953. The Origin of Life. 2nd Edition. Dover Publications.
Orgel, L. E. 1973. The Origins of Life: Molecules and Natural Selection. John Wiley and Sons.
Peterson, I. 1985. Proteinoids: Clues to Cellular Origins? BioScience 35(2):74-76. (February).
Pirie, N. W. 1954. On Making and Recognizing Life. New Biology 16: 41-53.
Prusiner, S. B. 1982. Novel Proteinaceous Infectious Particles Cause Scrapie. Science 216: 136-144. (9 April).
Prusiner, S. B. 1984. Prions. Scientific American 251(4): 50-59 (October).
Radetsky, P. 1990. Genetic Heretic. Discover 11(11): 78-84 (November).
Raloff, J. 1986. Clues to life's cellular origins. Science News 130(5): 71 (August 2)
Shapiro, R. 1986. Origins: A Skeptics Guide to the Creation of Life on Earth. Bantam Books.
Schopf, W. 1978. The Evolution of the Earliest Cells. Scientific American 239(3): 48-64.
Thaxton, C. B., W. L. Bradley and R. L. Olsen. 1984. The Mystery of Life's Origin: Reassessing Current Theories. Philosophical Library.
Trachtman, P. 1984. The Search for Life's Origins — and a first ‘synthetic cell' Smithsonian 15(3):42-51 (June).
West, E. S. and W. R. Todd. 1951. Textbook of Biochemistry. Macmillan Co.
White, A. D. 1960 (1895) A History of the Warfare of Science with Theology in Christendom. Dover Pub. in 2 vols.
(from Frank Sonleitner's critique of Of Pandas and People)