1. INTRODUCTION

The existence of initial life and its ability to replicate, would have depended on the availability of a variety of organic molecules that would have been present on an early sterile Earth, and which would have provided the support that allowed life to start. Once life began, these were supplanted later by inherently "biochemical" synthetic mechanisms.

For life to start required a variety of astrophysical and geological events to take place in the right location and at the right time (Joseph and Schild 2010). However, life did not become life, until it acquired the ability to reproduce. An essential feature of life, is its ability to reproduce, and to create identical and variable copies of itself. From consideration of contemporary biology, the initial event which triggered the creation of life, required that several necessary systems functioned together within a single phospholipid-like vesicle. This position is known as the "Vesicle First" principle. It is the position of this paper that the creation of a lipid vesicle provided the necessary environment for these events to take place simultaneously, coalescing to form self-replicating life.

Life's emergence was not gradual, but an all-or-none event; I suggest that it occurred when the processes for (1) metabolic energy generation, (2) for replication of nucleic acids, and for (3) catalysis were able to occur in concert inside a single vesicle in a suitable environment. At this point, cell growth and Darwinian evolution by mutation and selection could start and the cells, over generations, would become progressively more functional as additional "biochemical" systems were developed and incorporated.

2. THE FIRST CELL

Three systems, which would have arisen abiotically, were probably sufficient to start autocatalytic growth when they became present within a single closed vesicle. When they became embedded within a single "protocell", it became the First Cell and life began to replicate and to evolve. With less than these three different kinds of systems, life could not progress. It would fail to propagate, and not be able to evolve. I argued that with these few systems, growth and reproduction could occur and this made Darwinian evolution possible and for life to expand and to diversify.

3. THIS WORLD'S BIOHISTORY

The history of the life on Earth can be divided into many periods, e.g. prebiological, the first proto cell, the age of prokaryotes, followed by eukaryotes and increasingly complex life. Biological growth started once the ability to reproduce arose. The critical period that is discussed in this paper is how the reproduction ability might have arisen.

Only after a single vesicle became self-sufficient and self-reproducing could evolution in the Darwinian sense become possible. Then a biological version of at least seven more important abilities evolved. These are:

There are however, three other systems which must have originated spontaneously in a lifeless world: 1) The exploitation of environmental chemical energy for biological purposes via chemiosmosis, 2) Patterning of informational molecules by copying a strand of nucleic acids, 3) the synthesis of functional macromolecular catalysts first by nuclei acids and then by proteins. These three systems had to also become an an integral part in the earliest living cell. The other seven would likely have arisen by mutation and selection in later organisms that by then could replicate and evolve.

These seven processes, but on a non-biotic basis, must have functioned earlier, although poorly, prior to when life began. All (3 plus 7) were, and are, needed by all life forms in the modern biological world. The important thesis of this paper is that while the start of life had to wait until at least these three abiotic processes became associated with a single vesicle (or pre-cell), only after that could other systems have evolved a biological basis to support a diversity and the wealth of life forms.

4. THE NATURE OF THE MINIMUM PROCESSES THAT WERE NEEDED FOR LIFE TO START

The thesis presented here is that self-reproducing life did develop, but did not start full bloom. Initially, it was only poorly functional, and had only a few cellular systems that had minimal abilities that were needed for life to begin. Initially, these also had severe limitations and starting life must have depended to a large degree on additional support from environmental (abiotic) processes of many kinds. Although these three initial functions were the results of spontaneous chemical processes, later on when evolution could take place under the aegis of living and growing organisms operating under the Darwinian "mutation and selection" paradigm, they acquired a genetic basis. Thus, the position of this article is "Vesicles First" and "Genes Second." As cellular processes took over and became more effective and more varied, the functions developed further, and then individual cells of different kinds developed and came to behave as they do today.

Thus life began when all the essential elements and conditions were combined within one vesicle and this led to the First Cell and to growth and self-reproduction and then life as we know it.

4.1. The Processes for Trapping Energy from the Environment into a Usable Form. The mechanism of chemiosmosis would develop naturally on an early Earth (see Koch, 1985; Koch and Schmidt, 1991; Koch and Silver, 2005). This earliest energy transducing system depended on a closed vesicular structure and membrane components that could diffuse through it to carry components across. Vesicle could have arisen abiotically on a planet like earth, because the physical equivalent of phospholipids would have existed in this early, lifeless world. Those lipids, composed of a hydrocarbon chain with a polar group at one end, would spontaneously form into bilayers and that in turn would form closed bilayer vesicles. Formation of vesicles would occur in an aqueous environment due to physical forces, for example, from storm and wave action. The vesicular structure would make it possible to capture spontaneous bioenergy from the reaction of substances in the environment by chemiosmosis. Therefore, bioenergy in the environment made it possible for these vesicles to function long before the evolution of other bioenergy transduction mechanisms which are characteristic of life today. The lipid bilayers could have been permeated by non-polar molecules which could bind and transport polar molecules across the membrane.

All machines, living or not, require energy to make the essential processes go in the 'needed' way. If this is in the non-thermodynamic direction (i.e., not down-hill, but the up-hill), then energy input is needed. The major bioenergy mechanisms that have been considered (several kinds of fermentation, several kinds of photosynthesis, and respiration), could not apply to the First Cell and possibly not even to the Last Universal Common Ancestor (LUCA) and its earliest descendents. This is because photosynthesis, and probably, fermentation and oxygen-based respiration, almost certainly, evolved after the period of the LUCA. Moreover, all of the usual bioenergy couplings in today's systems are very complex processes and could not reasonably be imagined to have arisen in an abiotic environment. For example, fermentation requires a supply of fermentable resources, which are almost completely produced as the result of oxygenic photosynthetic systems, and therefore such resources were present in negligible amounts before oxygen producing photosynthesis developed.

Two possible original sources of biologically useable energy have been proposed. Both of these postulated first processes depended a chemiosmotic mechanism and do not have a phospho-anhydride basis, as mainly employed in most of the energetics carried on by Prokaryotes and Eukaryotes. One possible source was from extracting bioenergy from the coupling during the formation of iron pyrites (Koch, 1985; Koch and Schmidt, 1991; Koch and Silver, 2005) and is not further discussed here. The other proposed process is addressed below. It probably developed first and was the coupling of the reaction of CO₂ and H₂ to produce CH₄ and H₂O. These two exergonic processes are both quite different than the mechanisms of fermentation, photosynthesis, and the kinds of respirations that developed later. Both of these postulated 'early processes' depended on a chemiosmotic mechanism and do not have a phospho-anhydride basis, as mainly employed in most of the energetics carried on by modern Prokaryotes and Eukaryotes.

4.1.1 Methanogenesis as the first bioenergetic source energy. Methanogenesis must have arisen earlier than anaerobic or oxygen-producing photosynthesis or respiration. This chronology seems to be indicated by the geological record and the fact that the CO₂ and H₂ would have been abundant on the early Earth. Methogenesis occurs with a Free Energy of -310 kC/mole. This negative free energy is sufficient to favor life's needed processes.

Modern Archaea synthesizes the cofactors for the biochemical steps for the Archaeal process internally. Presumably, the cofactors originally arose abiotically. A set of cofactors was needed to react one molecule of carbon dioxide with four molecules of molecular hydrogen to form methane and water. The most important job of the entire set of cofactors in a biological system is to function to trap the energy from this reaction for use in growth and biosynthesis. Such transduction could allow the flow of Free Energy into a form that the organism could use to favor its growth.

This negative free energy is sufficient to favor life's needed biological processes. However of course, only if this energy can be trapped and metabolically coupled to needed exergonic (synthetic) reactions would the biology of life be supported. Wolfe (1996) and Thauer (1998) analyzed the very complex process of methanogenesis in Archaea, but neither author explicitly looked at it as a source of energy transduction from the environment to the biosphere. However, these are key features which made possible the onset of life.

Methanogenesis involves various complex organic cofactors. These are needed for the total methanogenesis process as it is carried out today by Archaea. These Archaeal chemistries are quite different than most biochemical processes familiar to students of bacteria, plants, and animals. The steps in methanogenesis, leading to life, involved much more elaborate cofactors than those in glycolysis or in the Krebs' cycle where the mechanism of substrate level phosphorylation is dominant. Nevertheless, they allowed the flow of Free Energy for the first time into a form that could favor the growth of the organisms.

The process of biological methanogenesis from CO₂and H₂ by Archaebacteria (see Fig. 4) starts with activation of the CO₂ by one of a unique organic molecule cofactor (methanofuran). In the first step, this reduction of carbon dioxide with molecular hydrogen produces a formyl group that is then transferred to another cofactor. Then, it is reacted with a second H₂ and thus further reduced. Then, with or without the aid of another cofactor, but together with third molecule of H₂ it is still further reduced. Finally, an enzyme transfers the product to another cofactor, which is then disproportionated into methane with a final input of reducing power from a fourth molecule of H₂. Note, that four hydrogen molecules are needed to make one methane molecule and that the net reaction is the conversion of carbon dioxide and molecular hydrogen to methane and water, and nothing more; that is, except the energy that is trapped and redirected for biological purposes.

The thrust is that before life could start, many ubiquitous organic molecules were involved in a series of organic reactions that generated methane and water. Methane formation would couple energy in this process by chemiosmosis into the biosphere of the primitive cell, by these or earlier versions of them, and thus become the energy source for life's start. This would be done somehow involving the cofactors of these steps.

This is quite different than chemical methane formation in the earlier lifeless Earth. But it is also quite different from the more modern biochemistries of plants, animals, and prokaryotes. Energy derived from methanogenesis does not involve phosphate, but does require a closed cell structure and action of the chemiosmotic process. The absence of phosphate on early Earth has been used as an argument against an Earthly abiogenesis (Joseph and Schild 2010). Methanogenesis as an energy source helps to over come these objections and supports the possibility that life began on Earth and permitted life to start.

4.1.2 Energy Coupling by Methanogenesis. To understand how organisms can extract useable energy, we must consider how Archaea operate. The scheme is shown in Figure 4. Methanogenesis involves a complex system of many steps, many cofactors, and catalysts to carry out methane formation. Thus, in the Archaea, these cofactors use many special organic molecules (and protein catalysts). One can hope to infer from the study of the processes in living Archaeal systems, how the energy available in methane formation could have been trapped in a way to drive cellular processes toward synthesis, growth, and cellular functions in the primordial first living system.

Hence, the process of basic reaction; i.e., CO₂ + 4H₂ → 2H₂O + CH₄, must have arisen earlier than anaerobic or oxygen-producing photosynthesis and oxygen use by respiration. This chronology seems to be indicated by the geological record (Joseph 2010), and the fact that the reactants needed for methanogensis would have been abundant on the early Earth. This reaction occurs with a Free Energy of -310 kC/mole. This negative free energy is sufficient to favor life's needed processes. However of course, only if this energy can be trapped and metabolically coupled to needed exergonic (synthetic) reactions would the processes of life be supported.

Archaeal chemistries are quite different than most biochemical processes familiar to students of bacteria, plants, and animals. The steps in methanogenesis involve much more elaborate cofactors than those in glycolysis or in the Krebs' cycle where the mechanism of substrate level phosphorylation is dominant. Modern Archaea synthesizes the cofactors for the biochemical steps of the Archaeal process internally. Presumably these cofactors originally arose abiotically by random assembly of atoms in a lifeless world. But the set are needed to react one molecule of carbon dioxide with four molecules of molecular hydrogen to form methane and water. The key job of this entire set of processes is to trap energy for growth and biosynthesis. For the earliest living creatures on earth, this transduction could have allowed the flow of Free Energy for the first time into a form that could favor the growth of the organisms.

The process of biological methanogenesis from CO₂ and H₂ by Archaebacteria starts with activation of the CO₂ by one of a unique organic molecule cofactor (methanofuran). In the first step, this reduction of carbon dioxide with molecular hydrogen produces a formyl group that is then transferred to another cofactor. Then, it is reacted with a second H₂ and thus further reduced. Then, with or without the aid of another cofactor, but together with third molecule of H₂, it is still further reduced. Finally, an enzyme transfers the product to another cofactor, which is then disproportionated into methane with a final input of reducing power from a fourth molecule of H₂. Note, that four hydrogen molecules are needed to make one methane molecule and that the net reaction is the conversion of carbon dioxide and molecular hydrogen to methane and water, and nothing more; that is, except the energy that is trapped and redirected for biological purposes.

The thrust is that before life could start many ubiquitous organic molecules were involved in a series of organic reactions that generated methane and water. This methane formation coupled energy by chemiosmosis into the biosphere of the primitive cell.

4.1.3. Coupling from methanogenesis to biochemistry of growth Evidently, the coupling depends on the flux inward of reactants and the outward flux of product this is where the thermodynamic energy develops. But more mechanistically, it depends on some of processes of the multi-step chemical processes of the conversion (see the bottom area of Fig. 4). From the free energy of these steps it follows that from CH₂-H₃MPT reaction onwards the bulk of the potential energy of the process is coupled.

4.2. Synthesis of informational molecules Since Watson and Crick's (1953) work, we have understood the importance of the existence of a kind of molecule that is capable of storing and then relaying information, i.e. DNA. From the ideas of Delbrück, this requires a unique polymeric structures and its ability to code for its self-replication. The variety of structures that can be formed of nucleic acids chains composed of four special kinds of purines and pyrimidines nucleotides is large and this variety can serve diverse purposes. While the variety is large, the dimension of the double-stranded helix is constant and this is an important constraint both for function and replication.

What does it take to do make a meaningful sequence that can be duplicated? The information-bearing chemical structure of nucleic acids requires two purine and two pyrimidine molecules. Polymeric strands of these function because the nucleic acid bases have heterocyclic rings with planar aromatic rigid structure of that gives them a fixed physical structure, and this together with the shape and rigidity of the sugar rings and the functional connective abilities of the phosphate groups is enough for the stability needed for accurate replication and information transfer of the coding strand of the duplex polymer.

Although that is a part of the role of nucleic acid chains, it is not sufficient: The key suggestion of Delbrück was that a double-stranded nucleic acid molecule is necessary that contains in one of its strands the coded message and in the other the template or pattern of the anti-message. When the strands are separated both can be copied to form two double-stranded helices. For the paired nucleic acid structure at any position on its length there are only four possibilities for the nucleotide pairs: A-T, T-A, G-C and C-G. Each of these hydrogen-bonded pairs has the same total length between the bonds of the phosphates at their ends. Thus the end-to-end distance is the same no matter which pair of heterocyclic bases or in which of the two possible orientations the pair is positioned. Thus, the adenine nucleotide (A) when hydrogen bonded to the thymidine nucleotide (T) creates the same phosphate-to-phosphate length as the guanine-cytosine pair (G-C). For this reason from the outside, the double stranded helix has the same width, no matter which pair is present. This is necessary, especially for the reproduction of the double-stranded molecule that has to be duplicated with its component hydrogen-bonded base pairs positioned in either of two orientations with either of the two different kinds of base pairs. Such a consistent phosphate-to-phosphate spacing would be important for the copying the structure. This anatomic arrangement also mediates the opening of the double-stranded helix and makes possible the nucleotide addition to growing replicative chains. Half of the possible errors, e.g., formation of Py/Py and Pu/Pu pairs, are avoided, thereby, because double stranded helices with these groupings would require different phosphate-to-phosphate spacing across the local diameter of the double helix. This would be, also, an important requirement for fusing a new nucleotide pair into a growing chain. Also note, that these two purine and the two pyrimidine bases employed in DNA or in RNA are special and other heterocyclic bases are, and were, somehow excluded from the living systems on earth. It can be presumed because this would result in the nucleic acid that could not be accurately copied and, therefore, a chain with them would not persist.

The pieces (nucleic acid bases, sugars, phosphates) only fit together in one way to elongate the growing nucleic acid chains. This allows both nucleic acid sister chains of a double-stranded structure to have the same information, although in a complementary form. Again, this property depends on the longer purines molecules uniquely binding to the shorter pyrimidines molecules. This is part of the biological reason that adenine only goes with thymine while guanine only goes with cytosine. The other part of the reason, of course, depends on the ability to donate and accept hydrogen bonds.

For this paper, the point is that in an abiotic early world, the ATGC scheme could work to cause growth, but reproductive life would permit no other heterocyclic base in the structure. The nucleic acid bases would have been initially formed chemically and the pairing to form double-stranded structure depends only on the principles of organic chemistry.

4.3. Synthesis of specific functional macromolecules using catalysts. Long linear molecules of amino acids in proteins or long single strands of polynucleotides of RNA can coil up in specific ways to form unique three-dimensional shapes that are dependent on their detailed base sequence. They will have various chemically functional groups projecting from their surfaces, which can form hydrogen bonds and possess charges to attach themselves to other molecules. Because of these factors, three-dimensional nucleic acid (and later) protein structures would arise that caused specific chemical reactions to the molecules that bind to them. Such polymers could arise abiotically, but could not be the generator of life until they could be heritably reproduced.

Such catalytic entities could speed reactions of molecules that might bind to them to go to lower energy levels (i.e., downhill, or spontaneously). What about reactions uphill? That is why an utilizable bioenergy source was so important for the start of life, and of course, needed for its continuation. So one of the essential steps in the initiation of life was the mechanism enabling external metabolic energy to be coupled to a substrate to raise it to a higher energy state so it would spontaneously couple to another molecule.

By the splitting of a 'high-energy' compound; the hydrolysis can force a second reaction to go in the endergonic direction; and in some sense, to go 'up-hill' to yield the compound that the cell needs for constructive biosynthesis. Additionally, it can be used for other kinds of cell processes. Chemiosomosis can do the same coupling (or driving) of biochemical reactions though less efficiently, but importantly, it can work only in a cell that has a closed plasma membrane. However, this process does not use a phosphate-linked coupling mechanism and special enzymes to drive a reaction as done later in time, when the more modern biochemistry came to function.

The essential point is that for the beginning of life, and of course, today, the driving of chemical reactions in their unfavorable direction was essential.

5. HOW LONG WAS THE MONOPHYLETIC PERIOD

Astrobiologists have usually suggested that life may have taken root on this planet about 4.2 billion years ago (Joseph, 2009, Joseph and Schild 2010), with definitive evidence of life dated to 3.8 billion years ago (Mojzsis, et al., 1996; Pflug, 1978). Most scientists agree that Earth was formed by 4.6 billion years ago (bya). On this basis, if life appeared by 4.2 billion years (Joseph and Schild, 2010; Nemchin et al. 2008; O'Neil et al. 2008), and was definitely present by 3.8 billion years, then there was at least 300 million years (beginning 4.6 bya) to encompass the monophyletic period in which the seven physiological systems already enumerated arose. Even if we accept that Earth could not have sustained life until around 4.2 bya, and given evidence of life by 3.8 bya, this would still provide the three, initially abiotic, systems essential for the start life and about the seven other systems, a 300 million year interval between the start and end of the monophyletic period. However, as many scientists have noted, 300 million years may not appear to have been sufficiently long for the development of a functional state of some cellular enzymes systems (Joseph and Schild 2010). During this time also, a variety of enzymes serving in the intermediary metabolism of a large variety of organic molecules had to evolve, including DNA. Following the evolution of DNA, life could rapidly diversity and evolve, aided by horizontal gene transfer (Joseph 2010, Joseph and Schild 2010). I have argued (Koch, 1985) that cell-to-cell transmission could not occur until viruses and transmissible plasmid were able to carry the genes from one cell to another cell and that this did not occur until after the earth's biosphere became diverse (i.e., well after the time of LUCA), and this position has been accepted by others (Joseph 2010).

Recent studies of zircon crystals (Valley, 2005; Valley et al., 2006) found in Australia, showed that that liquid water was first present on the earth's surface about 4.4 billion years ago. This was earlier than had been thought. The new information means that there was up to 300 million additional years for the monophyletic period to have lasted than had been estimated. This may well have been long enough for development of these seven additional systems without invoking either special 'supernatural' processes, those overcoming Joseph's (2009, Joseph and Schild 2010) objection to an Earthly abiogenesis, or an extra terrestrial origin of genes as advocated by Joseph (2009, 2010).

6. CONCLUSIONS

Assuming that life originated on Earth and followed a process that started with chemical reactions in an abiotic earth, at some point, an entity developed that was capable of autocatalytic growth and evolution: The First Cell.

The First Cell probably arose at the instant of time when, at least, three quite different processes came to function within a single lipid vesicle. All three are necessary for it's growth and reproduction. At that instant evolution started in the Darwinian sense. On this logic, energy-generation initially depended on chemiosmosis that could occur spontaneously in an enclosed vesicle to utilize (transduce) reactants available in an abiotic world, and trap the energy to favor biology. This new ability would be the basis of the generation of progressive evolution and stable diversity that was needed for the development of metabolic versatility, the development of effective cell physiological systems, and the diversity of living systems.

An important point proposed here is that the generation of this primeval First Cell was not dependent on having all the metabolic system that do function in modern organisms, but was dependent on the simultaneous inclusion of several systems of non biological, spontaneous origin within a single phospholipid-like vesicle. These abilities together could create the functional autocatalytic life process that gave rise to growth and, then, to division and, also, to heritable changes. These systems must have arisen from the chemistry and physics of natural processes on the Earth surface and must have functioned in the most primitive, earliest organism, but to begin with had no biological basis, as they do after evolution by the survival if the fittest became possible.