Darwin’s main contribution to modern biology was to make clear that all history of life on earth is dominated by a simple principle, which is usually summarised as 'descent with modification'. However, interpretations about how this modification is produced have been controversial. In light of the data provided by recent studies on molecular biology, developmental biology, genomics, and other biological disciplines we discuss, in this paper, how Darwin's theory may apply to two main 'types' of evolution: that occurring in the (...) prebiotic world and that regarding the acquisition of major key-innovations differentiating higher-taxa, which makes up part of the so-called macroevolution. We argue that these studies show that evolution is a fascinating, complex and multifaceted process, with different mechanisms drivin it on different occasions and in different places. (shrink)

We hypothesize that life began not with the first self‐reproducing molecule or metabolic network, but as a prebiotic ecology of co‐evolving populations of macromolecular aggregates (composomes). Each composome species had a particular molecular composition resulting from molecular complementarity among environmentally available prebiotic compounds. Natural selection acted on composomal species that varied in properties and functions such as stability, catalysis, fission, fusion and selective accumulation of molecules from solution. Fission permitted molecular replication based on composition rather than linear structure, while fusion (...) created composomal variability. Catalytic functions provided additional chemical novelty resulting eventually in autocatalytic and mutually catalytic networks within composomal species. Composomal autocatalysis and interdependence allowed the Darwinian co‐evolution of content and control (metabolism). The existence of chemical interfaces within complex composomes created linear templates upon which self‐reproducing molecules (such as RNA) could be synthesized, permitting the evolution of informational replication by molecular templating. Mathematical and experimental tests are proposed. BioEssays 28: 399–412, 2006. © 2006 Wiley Periodicals, Inc. (shrink)

Even the simplest cell exhibits a high degree of functional differentiation (FD) realized through several mechanisms and devices contributing differently to its maintenance. Searching for the origin of FD, we briefly argue that the emergence of the respective organizational complexity cannot be the result of either natural selection (NS) or solely of the dynamics of simple self-maintaining (SM) systems. Accordingly, a highly gradual and cumulative process should have been necessary for the transition from either simple self-assembled or self-maintaining systems of (...) functionless structural components to systems with FD. We follow results of recent in vitro experiments with respect to competition among protocells, where a primitive type of selection begins to operate among them accompanied by a parallel evolution of their functional domain. We argue that minimal forms of FD should be established within the evolution of SM processes in protocells as they undergo a simpler selection process for stability and persistence in a prebiotic environment. We then suggest the concept of closure of constraints (CoC) as a way to identify and describe minimal FD in a far-from-equilibrium SM organization. We show in detail how the concept of CoC together with the conditions for its fulfillment can be applied in the case of a simple protocellular system that begins to couple internal chemical reactions with the formation of its membrane components. Finally, we discuss how such SM systems can evolve towards significantly higher levels of FD, suggesting this is mainly the result of functional recombination (formation of mechanisms) in the context of a modular SM organization. (shrink)

Lately there has been a growing interest in evolutionary studies concerning how the regularities and patterns found in the living cell could have emerged spontaneously by way of self-assembly and self-organization. It is reasonable to postulate that the chemical compounds found in the primitive Earth would have mostly been very simple in nature, and would have been immersed in the natural dynamics of the physical world, some of which would have involved self-organization. It seems likely that some molecular processes self-organized (...) spontaneously into a hierarchy of complex behaviours. Our conceptual search herein reaches back to the time when prebiotic phenomena began to take shape. This was before the origin of life, so in this paper we hope to shed new light on some of the theoretical issues that surround the ways in which cellular organization might have evolved without the aid of replicated information. (shrink)

In this chapter we offer a critical analysis of organizational models about the process of origins of life and, thereby, a reflection about life itself (understood in a general, minimal sense). We begin by demarcating the idea of organization as an explanatory construct, linking it to the complex relationships and transformations that the material parts of (proto-)biological systems establish to maintain themselves under non-equilibrium dynamic conditions. The diverse ways in which this basic idea has been applied within the prebiotic field (...) are then reviewed in relative detail. We distinguish between “network” and “protocell” approaches, discussing their specific implications and explaining the greater relevance of the latter in the current state of affairs. Despite the key role that such organizational approaches play (and should keep playing) to advance on the problem of primordial biogenesis, the second half of our contribution is devoted to argue that they must be combined with other explanatory accounts, which go beyond the physiology of any single (proto-)organism. With that aim, we underline the fundamental differences between the autonomous, metabolic dynamics that individual (proto-)cells perform and the evolutionary and ecological dynamics that take place in a collective and trans-generational dimension. Apart from obvious gaps in the characteristic temporal and spatial scales involved, the corresponding causal and interactive regimes also reveal themselves as neatly distinct, what is reflected in the unpaired functional integration and the agent behavior displayed by biological individuals. Nevertheless, any living organism (and life in a wider, general sense) derives from the deep interweaving of those two phenomenological domains: namely, the “individual-metabolic” and the “collective-evolutionary” domains. At the end of the chapter, we propose the principle of dynamical decoupling as the core idea to develop a more comprehensive theoretical framework to understand how this intricate, causally asymmetric connection must be articulated during the actual process of biogenesis (as it happened here on Earth or anywhere else in the universe), so that life’s minimal complexity threshold is reached. (shrink)

We extend the comparatively simple processes of group symmetry-breaking in physical systems to groupoid/equivalence class phase transitions characterizing adiabatically, piecewise stationary, information transmission in prebiotic, biological, and social phenomena: High vs. Low probability paths $$\rightarrow$$ Interior and Exterior Interact $$\rightarrow$$ Multiple Interacting Tunable Workspaces Application to nonstationary processes seems possible via generalizations of the symmetry algebra, for example, to semigroupoids. The dynamic probability models explored here can be transformed into statistical tools for the analysis of real-time and other data across (...) a spectrum of important disciplines confronted by biological and other forms of cognition and their dysfunctions. (shrink)

Dietary fiber and prebiotics consistently modulate microbiota composition and function and hence may constitute a powerful tool in microbiota-gut-brain axis research. However, this is largely ignored in Hooks et al.’s analysis, which highlights the limitations of probiotics in establishing microbiome-mediated effects on neurobehavioral functioning and neglects discussing the potential of prebiotics in warranting the microbiota's role in such effects.

Since Darwin it is widely accepted that natural selection (NS) is the most important mechanism to explain how biological organisms—in their amazing variety—evolve and, therefore, also how the complexity of certain natural systems can increase over time, creating ever new functions or functional structures/relationships. Nevertheless, the way in which NS is conceived within Darwinian Theory already requires an open, wide enough, functional domain where selective forces may act. And, as the present paper will try to show, this becomes even more (...) evident if one looks into the problem of origins. If there was a time when NS was not operating (as it is quite reasonable to assume), where did that initial functional diversity, necessary to trigger off the process, come from? Self-organization processes may be part of the answer, as many authors have claimed in recent years, but surely not the complete one. We will argue here that a special type of self-maintaining organization, arising from the interplay among a set of different endogenously produced constraints (pre-enzymatic catalysts and primitive compartments included), is required for the appearance of functional diversity in the first place. Starting from that point, NS can progressively lead to new (and, at times, also more complex) organizations that, in turn, provide wider functional variety to be selected for, enlarging in this way the range of action and consequences of the mechanism of NS, in a kind of mutually enhancing effect. (shrink)

Our understanding of the complexity of the oral biome and of the role of the various constituent bacteria in the aetiology of dental disease is growing. Probiotics and their relationship with prebiotics, as well as other microbiome‐based interventions, could be useful in preventing and treating dental disease and in promoting oral health. However, given the promise and early stage of this treatment approach, there are also a number of ethical, social and regulatory issues associated with innovative probiotic therapy. In (...) this article, a brief update is given on contemporary theories of the aetiology and management of the two commonest dental diseases, and on the roles of pre‐ and probiotics and oral biome transplant in the management of these diseases. The focus is primarily on four core issues: informed consent, risk–benefit assessment, how to determine suitable healthy donors, and commercialization and regulation. We discuss the safety and benefits of oral probiotics, not only concerning the products and quality control during their manufacture, but also regarding the depth of public knowledge about this topic. We point out that the requirement of listing ingredients honestly might be insufficient, and that the prevalent rhetoric of ‘natural’ and ‘organic’ as well as some health claims in the translational, innovative probiotic industry and markets are themselves misleading and should be carefully scrutinized. Finally, we suggest an ethical imperative to find a balance between scientific research and industry, and public health in the regulation of probiotics. (shrink)

SummaryThe meaning of prebiotic evolution is first considered and analysed. The conclusion reached is that the phenomenon is both universal and predetermined, bringing interstellar molecules to the stage of proteins and DNA.Two important properties of living beings, evolution and senescence, are also discussed in depth from a new viewpoint.From this, dialectically, it is suggested that the first of the two phenomena corresponds to a progressive increase in the molecular weight of DNA, whereas the second is dependent on a decrease in (...) this.The theory on which the present research is based is in contradiction to that of the neo‐Darwinists. (shrink)

This paper calls attention to a philosophical presupposition, coined here the continuity thesis which underlies and unites the different, often conflicting, hypotheses in the origin of life field. This presupposition, a necessary condition for any scientific investigation of the origin of life problem, has two components. First, it contends that there is no unbridgeable gap between inorganic matter and life. Second, it regards the emergence of life as a highly probable process. Examining several current origin-of-life theories. I indicate the implicit (...) or explicit role played by the continuity thesis in each of them. In addition, I identify the rivals of the thesis within the scientific community — the almost miracle camp. Though adopting the anti-vitalistic aspect of the continuity thesis, this camp regards the emergence of life as involving highly improbable events. Since it seems that the chemistry of the prebiotic stages and of molecular self-organization processes rules out the possibility that life is the result of a happy accident, I claim that the almost miracle view implies in fact, a creationist position. (shrink)

Microbes in the gastrointestinal tract are under selective pressure to manipulate host eating behavior to increase their fitness, sometimes at the expense of host fitness. Microbes may do this through two potential strategies: (i) generating cravings for foods that they specialize on or foods that suppress their competitors, or (ii) inducing dysphoria until we eat foods that enhance their fitness. We review several potential mechanisms for microbial control over eating behavior including microbial influence on reward and satiety pathways, production of (...) toxins that alter mood, changes to receptors including taste receptors, and hijacking of the vagus nerve, the neural axis between the gut and the brain. We also review the evidence for alternative explanations for cravings and unhealthy eating behavior. Because microbiota are easily manipulatable by prebiotics, probiotics, antibiotics, fecal transplants, and dietary changes, altering our microbiota offers a tractable approach to otherwise intractable problems of obesity and unhealthy eating. (shrink)

Jakob von Uexküll's theories of life -- Biography and historical background -- Nature's conformity with plan -- Umweltforschung -- Biosemiotics -- Concluding remarks -- Marking a path into the environments of animals -- The essential approach to the organism -- Heidegger and the biologists -- Paths to the world -- Disruptive behavior : Heidegger and the captivated animal -- The worldless stone -- The poor animal -- For example, three bees and a lark -- Animal morphology -- A shocking wealth (...) -- A fine line in the rupture of time -- An affected body -- The theme of the animal melody : Merleau-Ponty and the umwelt -- The structure of behavior -- A pure wake, a quiet force -- A leaf of being -- Interanimality -- The-animal-stalks-at-five-oclock : Deleuze's affection for Uexküll -- Problematic organisms -- Uexküll's ethology of affects -- The body without organs, the embryonic egg, and prebiotic soup -- Nature's refrain sung across milieus and territories -- The animal stalks. (shrink)

A simple molecular system is described consisting of the reciprocal linkage between an autocatalytic cycle and a self-assembling encapsulation process where the molecular constituents for the capsule are products of the autocatalysis. In a molecular environment sufficiently rich in the substrates, capsule growth will also occur with high predictability. Growth to closure will be most probable in the vicinity of the most prolific autocatalysis and will thus tend to spontaneously enclose supportive catalysts within the capsule interior. If subsequently disrupted in (...) the presence of new substrates, the released components will initiate production of additional catalytic and capsule components that will spontaneously re-assemble into one or more autocell replicas, thereby reconstituting and sometimes reproducing the original. In a diverse molecular environment, cycles of disruption and enclosure will cause auto-cells to incidentally encapsulate other molecules as well as reactive substrates. To the extent that any captured molecule can be incorporated into the autocatalytic process by virtue of structural degeneracy of the catalytic binding sites, the altered autocell will incorporate the new type of component into subsequent replications. Such altered autocells will be progenitors of “lineages” with variant characteristics that will differentially propagate with respect to the availability of commonly required substrates. Autocells are susceptible to a limited form of evolution, capable of leading to more efficient, more environmentally fitted, and more complex forms. This provides a simple demonstration of the plausibility of open-ended reproduction and evolvability without self-replicating template molecules or maintenance of persistent nonequilibrium chemistry. This model identifies an intermediate domain between prebiotic and biotic systems and bridges the gap from nonequilibrium thermodynamics to life. (shrink)

The role of evolutionary theory at the origin of life is an extensively debated topic. The origin and early development of life is usually separated into a prebiotic phase and a protocellular phase, ultimately leading to the Last Universal Common Ancestor. Most likely, the Last Universal Common Ancestor was subject to Darwinian evolution, but the question remains to what extent Darwinian evolution applies to the prebiotic and protocellular phases. In this review, we reflect on the current status of evolutionary theory (...) in origins of life research by bringing together philosophy of science, evolutionary biology, and empirical research in the origins field. We explore the various ways in which evolutionary theory has been extended beyond biology; we look at how these extensions apply to the prebiotic development of (proto)metabolism; and we investigate how the terminology from evolutionary theory is currently being employed in state-of-the-art origins of life research. In doing so, we identify some of the current obstacles to an evolutionary account of the origins of life, as well as open up new avenues of research. (shrink)

Life appears to be a natural property of matter, but the problem of its origin only arose after early scientists refuted continuous spontaneous generation. There is no chance of life arising ‘all at once’, we need the standard scientific incremental explanation with large numbers of small steps, an approach used in both physical and evolutionary sciences. The necessity for considering both theoretical and experimental approaches is emphasized. After describing basic principles that are available (including the Darwin-Eigen cycle), the search for (...) origins is considered under four main themes. These are the RNA-world hypothesis; potential intermediates between an RNA-world and a modern world via the evolution of protein synthesis and then of DNA; possible alternatives to an RNA-world; and finally the earliest stages from the simple prebiotic systems to RNA. The triplicase/proto-ribosome theory for the origin of the ribosome is discussed where triples of nucleotides are added to a replicating RNA, with the origin of a triplet code well-before protein synthesis begins. The length of the code is suggested to arise from the early development of a ratchet mechanism that overcomes the problem of continued processivity of an RNA-based RNA-polymerase. It is probable that there were precursor stages to RNA with simpler sugars, or just two nucleotides, but we do not yet know of any better alternatives to RNA that were likely to arise naturally. For prebiotic stages (before RNA) a flow-reactor model is suggested to solve metabolism, energy gradients, and compartmentation simultaneously – thus the intense interest in some form of flow reactor. If an autocatalytic cycle could arise in such a system we would be major steps ahead. The most likely physical conditions for the origin of life require further clarification and it is still unclear whether the origin of life is more of an entropy (information) problem (and therefore high temperatures would be detrimental), rather than a kinetic problem (where high temperatures may be advantageous). (shrink)

The goal of synthetic biology is to create artificial organisms. To achieve this it is essential to understand what life is. Metabolism-replacement systems, or (M, R)-systems, constitute a theory of life developed by Robert Rosen, characterized in the statement that organisms are closed to efficient causation, which means that they must themselves produce all the catalysts they need. This theory overlaps in part with other current theories, including autopoiesis, the chemoton, and autocatalytic sets, all of them invoking some idea of (...) closure. A simple model of an (M, R)-system has been implemented in the computer, and behaves in ways that may shed light on the requirements for a prebiotic self-organizing system. In addition to a trivial steady state in which nothing happens, it can establish a non-trivial steady state in which all intermediates have finite concentrations, with their rates of degradation balanced by their rates of synthesis. The system can be regenerated from the set of food components plus a single intermediate, and maintain itself in that state indefinitely, despite continuous degradation. At the very low compartment volumes that may have existed in prebiotic conditions, for example in cavities in minerals, or in micelles formed by simple amphiphiles, statistical fluctuations in the numbers of molecules need to be taken into account. With the stochastic approach there is no non-trivial steady state in strict mathematical terms, because the system will always collapse to the trivial state after sufficient time. However, the average time before collapse is so long for volumes greater than $10^{-19}\;{\textsc{l}}$ (much smaller than the volume of the order of $10^{-15}\;{\textsc{l}}$ for a typical bacterial cell) that for practical purposes the self-maintaining state of non-null concentrations becomes significant, recalling the situation of bistability that is observed in deterministic analysis. In turn, there exists a minimum size below which the self-organizing system cannot maintain itself on chemically relevant time scales. The value of the critical volume depends on the particular concentrations and rate constants assumed, but the principle could apply generally. (shrink)

During the last two decades, a new understanding of life emerged at the forefront of science.The development of complexity theory, technically known as nonlinear dynamics, has allowed scientists and mathematicians to model the complexities of living systems in new ways that have yielded many important discoveries. In this article, the author reviews the basic concepts, current achievements and status of complexity theory from the perspective of the new understanding of biological life. Models and theories discussed include the theory of dissipative (...) structures for nonlinear chemical systems, the application of bifurcation theory to genetic networks and cell differentiation, the study of the origin of biological form, a new approach to the understanding of developmental stability in embryology, and a model of the ‘origin of life’ and prebiotic evolution in tiny, membrane-bounded vesicles in the primeval oceans. (shrink)

The term biology is of Greek origin meaning the study of life. On the other hand, chemistry is the science of matter, which deals with matter and its properties, structure, composition, behavior, reactions, interactions and the changes it undergoes. The theory of abiogenesis maintains that chemistry made a transition to biology in a primordial soup. To keep the naturalistic ‘inanimate molecules to human life’ evolution ideology intact, scientists must assemble billions of links to bridge the gap between the inanimate chemicals (...) that existed in the primordial soup and anatomically modern humans. Even though the proponents of a natural origin of life expressed much optimism for providing their theories, presently there is a detailed compilation of information seriously questioning this doctrine. This reductionistic ideology has always failed to answer two simple questions: (1) What is the minimum number of parts that are essential for a living organism to survive? (2) By what mechanism do these parts get assembled together? Evolutionists say a series of prebiotic processes and developments guide networks of dynamically linked small molecules and amphiphiles to form biological macromolecules, membraneous compartments, and finally primitive cells. However, none of these proposed pathways to life appears to be credible. The continuous advancement in various fields of science are not only providing major challenges to reductionistic ideology but are supplying increasing evidence for a systemic concept of life as an organic whole. Several leading researchers in the field of ‘origin of life’ are continually concluding that there are major scientific problems attached with all existing naturalistic ‘origin of life’ hypothesis. Only by taking into account all biological activities collectively as a system can a satisfactory elucidation of the living state be realized. In this present paper an attempt has been made to present a few significant challenges to the theory of abiogenesis based on the peer reviewed scientific literature. Subsequently, a non-reductionistic concept of life as a system is proposed as an alternative for resolving some of the problems inherent in origin of life research. (shrink)

This volume is the latest in a series of books and articles stretching back more than three decades on a theme quite startling in its claims and implications: that terrestrial life did not originate on Earth but arrived in the form of cells or bacteria from outer space. The idea of “panspermia,” that the seeds of life are spread from planet to planet, dates to the 19th century with the ideas of Lord Kelvin. It was championed by the Swedish physicist, (...) chemist, and Nobelist Svante Arrhenius at the beginning of the 20th century. Once scientists recognized the difficulties of life surviving in the conditions of interplanetary and interstellar space, by the 1960s a neo-panspermia became popular: not life itself, but prebiotic chemicals were the new seeds of life, made more likely by the discovery of numerous complex organic molecules in meteorites, comets, and interstellar molecular clouds. But the difficulties of synthesizing anything more complicated than amino acids in the wake of the famous Miller-Urey experiment in 1953 kept alive the idea that life itself may be spread throughout the universe. At the center of this work is Chandra Wickramasinghe, a research student of the maverick astronomer Fred Hoyle. In 1962 Hoyle became interested in the origin and nature of interstellar dust, in particular as found in dense molecular clouds, and he and Wickramasinghe set to work on the problem. They became convinced that dust could not form inside molecular clouds, but must have originated in the atmospheres of cool stars, protoplanetary discs, or supernova ejecta, a theory now widely accepted. It was the next steps that became increasingly controversial: that the spectroscopic signature of dust was best explained by complex biomolecules such as cellulose; that biomolecules were assembled into still more complex forms inside comets; and that the living cells and bacteria generated there were responsible for the origin of life on Earth. And not only that: Hoyle and Wickramasinghe argued that the delivery of bacteria from space continues, affecting both the origin and the ongoing evolution of life, and may even be responsible for certain diseases on Earth. These theories were not only reported in reputable scientific journals such as Nature, but also in popular books including Lifecloud (1978), Diseases from Space (1979), and Evolution from Space (1981). Biologists were not impressed; Lynn Margulis, not known for the timidity of her own theories such as endosymbiosis, called the first book “wanton, amusing, promiscuous fiction.”. (shrink)

Here, I propose a new hypothesis: sex originated from an archaic gene transfer process among prebiotic bubbles without the prerequisite for reproduction. This de‐coupling from reproduction might make the thorny problem of accounting for the evolution of sex, despite the apparent advantages of parthenogenicity, more tractable.

Some theoretical examples of possibilities for natural selection in a prebiotic organic medium at the molecular level are given. These examples, presented in the form of simple kinetic models, are based on the idea that the occurrence of autocatalysis and self-duplication broke through the limitations imposed by contacts by chance with rare but essential molecules in the surrounding medium. It is shown that many regulatory mechanisms and the development of organization are logical consequences of this selection process. Symbiogenetic associations might (...) play a role in producing more efficiently duplicating systems. The peculiar circumstances prevailing during pre-biological evolution, including the chance of irregular duplications and the possibilities for the uptake of systems from the surrounding medium, suggest the accumulation in this phase of evolution of a vast amount of genetic information whose potentialities became manifest during the subsequent biological evolution. (shrink)

It is a most commonly accepted hypothesis that life originated from inanimate matter, somehow being a synthetic product of organic aggregates, and as such, a result of some sort of prebiotic synthetic biology. In the past decades, the newly formed scientific discipline of synthetic biology has set ambitious goals by pursuing the complete design and production of genetic circuits, entire genomes or even whole organisms. In this paper, I argue that synthetic biology might also shed some novel and interesting perspectives (...) on the question of the origin of life, and that, in addition, it might challenge our most commonly accepted definitions of life, thereby changing the ways we might think about life and its origin. (shrink)

This paper follows the circuitous path of theories concerning the origins of viruses from the early years of the twentieth century until the present, considering RNA viruses in particular. I focus on three periods during which new understandings of the nature of viruses guided the construction and reconstruction of origin hypotheses. During the first part of the twentieth century, viruses were mostly viewed from within the framework of bacteriology and the discussion of origin centered on the “degenerative” or the “retrograde (...) evolution theory.” However, concomitantly, in the context of origin-of-life theorizing, the notion that viruses are vestiges of a prebiotic world was also being contemplated. In the 1960s the idea that viruses were genetic elements that “escaped” from cells became prevalent. These traditional hypotheses are being revisited nowadays by evolutionary virologists, who have placed them within a new conceptual framework that is supported by cutting-edge genomic and proteomic data. Two current, opposing scenarios of virus origin are presented. The philosophical dimensions of “revisiting” the original hypotheses are briefly discussed. (shrink)

Modern cells present no signs of a putative prebiotic RNA world. However, RNA coding is not a sine qua non for the accumulation of catalytic polypeptides. Thus, cellular proteins spontaneously fold into active structures that are resistant to proteolysis. The law of mass action suggests that binding domains are stabilized by specific interactions with their substrates. Random polypeptide synthesis in a prebiotic world has the potential to initially produce only a very small fraction of polypeptides that can fold spontaneously into (...) catalytic domains. However, that fraction can be enriched by proteolytic activities that destroy the unfolded polypeptides and regenerate amino acids that can be recycled into polypeptides. In this open system scenario the stable domains that accumulate and the chemical environment in which they are accumulated are linked through self coding of polypeptide structure. Such open polypeptide systems may have been the precursors to the cellular ribonucleoprotein (RNP) world that evolved subsequently. (shrink)

Life is characterized by a selectivity for asymmetric molecules. A great deal of theoretical and experimental work has yet to explain why living organisms utilize only L‐amino acids in proteins and D‐sugars in RNA and DNA. Also unknown is how a form of life based on asymmetric molecules evolved from an environment containing a racemic mixture of prebiotic molecules. By what mechanism did this selectivity for asymmetric molecules take place?

One of the most influential physics books of the twentieth century was actually about biology. In a series of lectures, Erwin Schrödinger described how he believed that quantum mechanics, or some variant of it, would soon solve the riddle of life. These lectures were published in 1944 under the title What is life? and are credited by some as ushering in the age of molecular biology. In the nineteenth century, many scientists thought they knew the answer to Schrödinger’s rhetorical question. (...) Life, they maintained, was some sort of magic matter. The continued use of the term ‘organic chemistry’ is a hangover from that era. The belief that there is a chemical recipe for life led to the hope that, if only we knew what it was, we could mix up the right stuff in a test tube and make life in the lab. Most research on biogenesis has followed that tradition, by assuming that chemistry was a bridge — and a long one at that — linking matter with life. Elucidating this chemical pathway has been a tantalizing goal, spurred on by the famous Miller–Urey experiment of 1952, in which amino acids were made by sparking electricity through a mixture of water and common gases. But the concept has turned out to be something of a blind alley, and further progress with prebiotic chemical synthesis has been frustratingly slow. The origin of life remains one of the great outstanding mysteries of science. To take up Schrödinger’s suggestion, a radical solution to the problem, ‘What is life?’ could be that quantum mechanics enabled life to emerge directly from the atomic world, without the need for complex intermediate chemistry. Life must have a chemical basis: organic molecules provide the hardware for biology. But what about the software? When Schrödinger asked, ‘What is life?’ he could already glimpse the central significance of the cell’s information storage and replication processes, even though the role of DNA and the genetic code was yet to be discovered.. (shrink)

Emmanuel Davoust, an internationally known specialist on galaxies, explores such major themes and topics of debate as prebiotic chemistry and paleovisits, in this lucid investigation of the continuing search for extraterrestrial life.

The Oparin hypothesis from 1936 was a milestone in the origin of life research, making a model that was at least in part empirically testable, and changing the course of life studies from a long tradition of metaphysics to a scientific domain of investigation. His hypothesis is based on the idea of the prebiotic synthesis of macromolecules as a fundamental step on the road to first life. Although the Oparin hypothesis brought fresh ideas and concepts, in its description of the (...) steps in the hypothesized transition from the inorganic to the organic world in detail, today some premises are considered unconfirmed, uncertain, or even rejected. With high respect to its metatheoretical reach and scientific impact on prebiotic chemistry, pushing the origin of first life research into an empirical context, from a contemporary viewpoint, its contribution is highly limited in the area of history of science and history of philosophy (of science). Keywords: biology, history of science, Oparin, origin of life, philosophy of science. (shrink)

If the coming of the last universal cellular ancestor marks the crossing of the “Darwinian Threshold”, pre-LUCA evolution must have been pre-Darwinian. But how did pre-Darwinian evolution actually operate? Bringing together and extending insights from both earlier and more recent contributions, this essay advances three principal arguments regarding the pre-Darwinian evolution. First, in the pre-Darwinian epoch, survival essentially meant persistence within the prebiotic system, and it depended mostly on chemical variation and interaction. Second, selection operated upon four different properties: chemical; (...) chemical-physical; vesicles’ capacities in absorbing, engulfing, and merging; and protocells’ coupling of metabolism, replication, and division. Third, division evolved from a state without tight coupling of replication with division to a state of tight coupling. Eventually, protocells with a tight coupling of replication with division became the First Universal Cellular Ancestors and then LUCA. (shrink)

This book aims at providing a brief but broad overview of biosignatures. The topics addressed range from prebiotic signatures in extraterrestrial materials to the signatures characterising extant life as well as fossilised life, biosignatures related to space, and space flight instrumentation to detect biosignatures either in situ or from orbit. The book ends with philosophical reflections on the implications of life elsewhere. In the 15 chapters written by an interdisciplinary team of experts, it provides both detailed explanations on the nature (...) of biosignatures as well as useful case studies showing how they are used and identified in ancient rocks, for example. One case study addresses the controversial finding of traces of fossil life in a meteorite from Mars. The book will be of interest not only to astrobiologists but also to terrestrial paleontologists as well as any reader interested in the prospects of finding a second example of life on another planet. (shrink)

RésuméCet exposé repose essentiellement sur des idées originates déjà développées par ľauteur. En fait, les concepts en cause, à savoir ľévolution prébiotique et biotique, ainsi que la sénescence et le cancer, sont rassemblés dans une théorie profoundément unitaire résultant, soit de ľaccroissement, soit de la diminution, du poids moléculaire du DNA.Ceci s'apparente singulièrement à la révolution de la physique dans ce premier quart de siècle qui a conduit àľélaboration de la théorie de la relativité et de la mécanique ondulatoire.SummaryThis paper (...) is based essentially on original ideas already developed by the author. In fact the concepts considered, that is to say prebiotic and biotic evolution as well as ageing and cancer, are brought together into a highly unified theory resulting from the increase or the lowering of the molecular weight of DNA.This is closely in agreement with the revolution in physics which took place in the first quarter of this century and which led both to the theory of relativity and of wave mechanics.ZusammenfassungDie Arbeit beruht im wesentlichen auf vom Verfasser schon früher entwickelten Originalge‐danken. Die involvierten Begriffe, die vorbiotische und die biotische Evolution sowie das Altern und die Wucherung, finden sich in der Tat in einer einheitlichen Theorie vereinigt, die aus der Zunahme oder Abnahme des Molekulargewichts des DNA resultiert.Dies stimmt auffällig mit der Revolution in der Physik überein, die im ersten Viertel unseres Jahrhunderts zur Ausarbeitung der Relativitätstheorie und der Wellenmechanik geführt hat. (shrink)

It is commonly presumed that abiotic membranes were colonized by proteins later on. Yet, hydrophobic peptides could have formed primordial protein‐dominated membranes on their own. In a metabolism‐first context, “autocatalytically closed” sets of statistical peptides could organize a self‐maintaining protometabolism, assisted by an unfolding set of ribotide‐related cofactors. Pairwise complementary ribotide cofactors may have formed docking guides for stochastic peptide formation, before replicating RNA emerged from this subset. Tidally recurring wet‐drying cycles and an early onset of photosynthetic activities are considered (...) most likely to meet the thermodynamic requirements. Conceivably, the earliest peptide‐dominated vesicles were engaged in light harvesting, together with isoprenoid‐tethered pigments, rather than providing an external boundary. Early on, the bulk of prebiotic organic matter can have formed a contiguous layer covering the mineral sediment, held in place by colloidal coherence of a hydrogel matrix. This unconventional scenario assumes a late onset of cellular individualization – perhaps from within, resembling endosporogenesis. (shrink)

Molecular imprints of organisms serving as both the agents and the products of the underlying sign activities are quantum mechanical in their origins. In particular, molecules in any reaction networks constituting a biological organism are semiotic or context-dependent in the sense that their activities reside within the proper coordination of the entire networks. The origin of life could have been related to a specific aspect of molecular semiotics, especially in the transition from molecules as the physical symbols of material units (...) to molecules as the semiotic signs having the capacity of pointing to something else other than the molecules themselves. Quantum mechanical underpinning of the molecular imprints leading to the emergence of life is in the appraisal of the material capacities of both coherent assimilation and decoherent dissociation already latent in the imprints. One empirical evidence suggesting the likelihood of both coherent assimilation and decoherent dissociation in prebiotic settings could have been found in synthetic chemical reactions running in hydrothermal circulation of seawater through hot vents in the Haedean ocean on the primitive Earth. (shrink)

The central dogma of molecular biology dictates that, with only a few exceptions, information proceeds from DNA to protein through an RNA intermediate. Examining the enigmatic steps from prebiotic to biological chemistry, we take another road suggesting that primordial peptides acted as template for the self-assembly of the first nucleic acids polymers. Arguing in favour of a sort of archaic “reverse translation” from proteins to RNA, our basic premise is a Hadean Earth where key biomolecules such as amino acids, polypeptides, (...) purines, pyrimidines, nucleosides and nucleotides were available under different prebiotically plausible conditions, including meteorites delivery, shallow ponds and hydrothermal vents scenarios. Supporting a protein-first scenario alternative to the RNA world hypothesis, we propose the primeval occurrence of short two-dimensional peptides termed “selective amino acid- and nucleotide-matching oligopeptides” (henceforward SANMAOs) that noncovalently bind at the same time the polymerized amino acids and the single nucleotides dispersed in the prebiotic milieu. In this theoretical paper, we describe the chemical features of this hypothetical oligopeptide, its biological plausibility and its virtues from an evolutionary perspective. We provide a theoretical example of SANMAO’s selective pairing between amino acids and nucleosides, simulating a poly-Glycine peptide that acts as a template to build a purinic chain corresponding to the glycine’s extant triplet codon GGG. Further, we discuss how SANMAO might have endorsed the formation of low-fidelity RNA’s polymerized strains, well before the appearance of the accurate genetic material’s transmission ensured by the current translation apparatus. (shrink)

Emergence, a hot topic of discussion for the last several years, has implications not only for the study of science but also for theology. I survey Philip Clayton's book Mind & Emergence , drawing from it and applying some of its philosophical principles to a theological interpretation of emergence. This theological interpretation is supplemented by a brief examination of relevant biblical usages of the term kenosis. From this exploration of kenosis, I assert that the Spirit is kenotically poured into creation, (...) which onsets the long and laborious process of prebiotic evolution, leading to biological evolution toward increasing complexity. The complexification of matter, then, has its ontological origin in and through the agency of the Spirit of God. As such, the concept of creatio continua , continuing creation, is defended. The Spirit enables emergence by endowing creation and creatures with the ability to unfold by apparent natural processes according to their own inherent potentialities and possibilities. This essay contributes to a systematic theology of creation by constructing a theological synthesis between kenosis and emergence. (shrink)

In this review, we describe some of the central philosophical issues facing origins-of-life research and provide a targeted history of the developments that have led to the multidisciplinary field of origins-of-life studies. We outline these issues and developments to guide researchers and students from all fields. With respect to philosophy, we provide brief summaries of debates with respect to (1) definitions (or theories) of life, what life is and how research should be conducted in the absence of an accepted theory (...) of life, (2) the distinctions between synthetic, historical, and universal projects in origins-of-life studies, issues with strategies for inferring the origins of life, such as (3) the nature of the first living entities (the “bottom up” approach) and (4) how to infer the nature of the last universal common ancestor (the “top down” approach), and (5) the status of origins of life as a science. Each of these debates influences the others. Although there are clusters of researchers that agree on some answers to these issues, each of these debates is still open. With respect to history, we outline several independent paths that have led to some of the approaches now prevalent in origins-of-life studies. These include one path from early views of life through the scientific revolutions brought about by Linnaeus (von Linn.), Wöhler, Miller, and others. In this approach, new theories, tools, and evidence guide new thoughts about the nature of life and its origin.We also describe another family of paths motivated by a” circularity” approach to life, which is guided by such thinkers as Maturana & Varela, Gánti, Rosen, and others. These views echo ideas developed by Kant and Aristotle, though they do so using modern science in ways that produce exciting avenues of investigation. By exploring the history of these ideas, we can see how many of the issues that currently interest us have been guided by the contexts in which the ideas were developed. The disciplinary backgrounds of each of these scholars has influenced the questions they sought to answer, the experiments they envisioned, and the kinds of data they collected. We conclude by encouraging scientists and scholars in the humanities and social sciences to explore ways in which they can interact to provide a deeper understanding of the conceptual assumptions, structure, and history of origins-of-life research. This may be useful to help frame future research agendas and bring awareness to the multifaceted issues facing this challenging scientific question. (shrink)

The systems view on life and its emergence from complex chemistry has remarkably increased the scientific attention on metabolism in the last two decades. However, during this time there has not been much theoretical discussion on what constitutes a metabolism and what role it actually played in biogenesis. A critical and updated review on the topic is here offered, including some references to classical models from last century, but focusing more on current and future research. Metabolism is considered as intrinsically (...) related to the living but not necessarily equivalent to it. More precisely, the idea of “minimal metabolism”, in contrast to previous, top‐down conceptions, is formulated as a heuristic construct, halfway between chemistry and biology. Thus, rather than providing a complete or final characterization of metabolism, our aim is to encourage further investigations on it, particularly in the context of life's origin, for which some concrete methodological suggestions are provided. Also see the video abstract here:https://youtu.be/DP7VMKk2qpA. (shrink)