Biogenesis

Precursor compounds for abiotic proto cellular membranes are necessary for the origin of life. Amphipathic compounds such as fatty acids and acyl glycerols are important candidates for micelle/bilayer/vesicle formation. Two sets of experiments were conducted to study dehydration reactions of model lipid precursors in aqueous media to form acyl polyols and wax esters, and to evaluate the stability and reactions of the products at elevated temperatures. In the first set, mixtures of n-nonadecanoic acid and ethylene glycol in water, with and without oxalic acid, were heated at discrete temperatures from 150 • C to 300 • C for 72 h. The products were typically alkyl alkanoates, ethylene glycolyl alkanoates, ethylene glycolyl bis-alkanoates and alkanols. The condensation products had maximum yields between 150 • C and 250 • C, and were detectable and thus stable under hydrothermal conditions to temperatures <300 • C. In the second set of experiments, mixtures of n-heptanoic acid and glycerol were heated using the same experimental conditions, with and without oxalic acid, between 100 • C and 250 • C. The main condensation products were two isomers each of monoacylglycerols and diacylglycerols at all temperatures, as well as minor amounts of the fatty acid anhydride and methyl ester. The yield of glyceryl monoheptanoates generally increased with increasing temperature and glyceryl diheptanoates decreased noticeably with increasing temperature. The results indicate that condensation reactions and abiotic synthesis of organic lipid compounds under hydrothermal conditions occur easily, provided precursor concentrations are sufficiently high.

Dehydration/condensation reactions between organic molecules in the prebiotic environment increased the inventory and complexity of organic compounds available for self-assembly into primitive cellular organisms. As a model of such reactions and to demonstrate this principle, we have investigated the esterification reaction between glycerol and decanoic acid that forms glycerol monodecanoate (GMD). This amphiphile enhances robustness of self-assembled membranous structures of carboxylic acids to the potentially disruptive effects of pH, divalent cation binding and osmotic stress. Experimental variables included temperature, water activity and hydrolysis of the resulting ester product, providing insights into the environmental conditions that would favor the formation and stability of this more evolved amphiphile. At temperatures exceeding 50 degrees C, the ester product formed even in the presence of bulk water, suggesting that the reaction occurs at the liquid interface of the two reactants and that the products segregate in the two immiscible layers, thereby reducing hydrolytic back reactions. This implies that esterification reactions were likely to be common in the prebiotic environment as reactants underwent cycles of wetting and drying on rare early landmasses at elevated temperatures.

Because of the continuous focusing of thermal and chemical energy, ancient submarine hot springs are contenders as sites for the origin of life. But it is generally assumed that these would be of the acid and high-temperature 'black smoker' variety (Corliss et al., 1981). In fact today the greater part of the ocean circulates through off-ridge springs where it issues after modification at temperatures of around 40 °C or so but with the potential to reach 200 °C. Such offridge or ridge-flank springs remind us that there are other candidate sites for the origin of life. Although there is no firm indication of the pH of these off-ridge springs we have argued that the solutions are likely to be alkaline rather than acid. We test the feasibility of this idea using EQ geochemical water-rock interaction modelling codes (Wolery 1983) and find that for a range of possible initial chemistries of Hadean seawater, the pH of issuing solutions at around 200 °C is around one or more units alkaline. Such pH values hold for interaction with both basaltic and komatiitic crust. The robustness of this result suggests to us that alkaline submarine springs of moderate temperature, carrying many hundreds of ppm HS-to the ocean basins, are also serious contenders as sites for the origin of life, particularly as Hadean seawater was probably slightly acid, with a dissolved iron concentration approaching 100 ppm. On mixing of these solutions, supersaturation, especially of iron sulphide, would lead to the precipitation of colloidal gels. In our view iron sulphide was the likely substance of, or contributor to, the first vesicle membranes which led to life, as the supply of organic molecules would have been limited in the Hadean. Such a membrane would have had catalytic properties, expansivity, and would have maintained the natural chemiosmotic gradient, a consequence of the acid ocean and the alkaline interior to the vesicles.

Questions concerning the nature and origin of living systems and the hierarchy of their evolutionary processes are considered, and several problems which arise in connection with formerly developed theories--the autopoiesis of Maturana & Varela, the POL theory of Haukioja and the earlier developed evolutionary theory of Csfinyi--are discussed. The organization of living systems, the use of informational terms and the question how reproduction can enter into their characterization, problems of autonomy and identity are included in the list. It is suggested that replication--a copying process achieved by a special network of interrelatedness of components and component-producing processes that produces the same network as that which produced them--characterizes the living organization. The information "used" in this copying process, whether it is stored by special means or distributed in the whole system, is called replicative information. A theoretical model is introduced for the spontaneous emergence of replicative organization, called autogenesis.

The complexity of life boils down to the definition: "self-sustained chemical system capable of undergoing Darwinian evolution" [1]. The term "self-sustained" implies a set of chemical reactions capable of harnessing energy from the environment, using it to carry out programmed anabolic and catabolic functions. We briefly present our opinion on the general validity of this definition.

There is no broadly accepted definition of &#39;life.&#39; Suggested definitions face problems, often in the form of robust counter-examples. Here we use insights from philosophical investigations into language to argue that defining &#39;life&#39; currently poses a dilemma analogous to that faced by those hoping to define &#39;water&#39; before the existence of molecular theory. In the absence of an analogous theory of the nature of living systems, interminable controversy over the definition of life is inescapable.

It is commonly accepted among origin-of-life scientists that the emergence of life was an evolutionary process involving at one stage or other the working of natural selection. Researchers disagree, however, on the nature of the chemical infrastructure that could have formed prebiotically, enabling the evolutionary process. The division of the origin-of-life research community into ‘geneticists’ and ‘metabolists’ usually revolves around the issue whether the first to arise prebiotically was a genetic polymer or a primitive metabolic system. In this paper I offer an alternative classification based on the attitude to the onset of natural selection. From this perspective I add to the conventional division between gene-first and metabolism-first groups a position I call “preparatory metabolism”. By this line of thought, an RNA or an RNA-like polymer could not have emerged prebiotically. Nevertheless, the onset of natural selection had to wait until such a polymer had arised. This paper examines the RNA-first, RNA-later, metabolism-first and preparatory-metabolism scenarios, assessing the weaknesses and strengths of each. I conclude that despite the recent theoretical advances in all these lines of research, and despite experimental breakthroughs, especially in overcoming several RNA-first hurdles, none of the examined paradigms has yet attained decisive experimental support. Demonstrating the evolvability of a potentially prebiotic infrastructure, whether genetic or metabolic, is a most serious challenge. So is the experimental demonstration of the emergence of such an infrastructure under prebiotic conditions. The current agenda before origin-of-life researchers of all stripes and colors is the search for the experimental means to tackle all these difficulties.

The discovery of hydrothermal vents at oceanic ridge crests and the appreciation of their importance in the element balance of the oceans is one of the main recent advances in marine geochemistry 1 . It is likely that vents were present in the oceans of the primitive Earth because the ...

The origins of life on Earth required the establishment of self-replicating chemical systems capable of maintaining and evolving biological information. In an RNA world, single self-replicating RNAs would have faced the extreme challenge of possessing a mutation rate low enough both to sustain their own information and to compete successfully against molecular parasites with limited evolvability. Thus theoretical analyses suggest that networks of interacting molecules were more likely to develop and sustain life-like behaviour. Here we show that mixtures of RNA fragments that self-assemble into self-replicating ribozymes spontaneously form cooperative catalytic cycles and networks. We find that a specific three-membered network has highly cooperative growth dynamics. When such cooperative networks are competed directly against selfish autocatalytic cycles, the former grow faster, indicating an intrinsic ability of RNA populations to evolve greater complexity through cooperation. We can observe the evolvability of networks through in vitro selection. Our experiments highlight the advantages of cooperative behaviour even at the molecular stages of nascent life.

Astrobiologists are aware that extraterrestrial life might differ from known life, and considerable thought has been given to possible signatures associated with weird forms of life on other planets. So far, however, very little attention has been paid to the possibility that our own planet might also host communities of weird life. If life arises readily in Earth-like conditions, as many astrobiologists contend, then it may well have formed many times on Earth itself, which raises the question whether one or more shadow biospheres have existed in the past or still exist today. In this paper, we discuss possible signatures of weird life and outline some simple strategies for seeking evidence of a shadow biosphere.

The discovery of extra-solar planets is one of the greatest achievements of modern astronomy. The detection of planets with a wide range of masses demonstrates that extra-solar planets of low mass exist. In this paper we describe a mission, called Darwin, whose primary goal is the search for, and characterization of, terrestrial extrasolar planets and the search for life. Accomplishing the mission objectives will require collaborative science across disciplines including astrophysics, planetary sciences, chemistry and microbiology. Darwin is designed to detect and perform spectroscopic analysis of rocky planets similar to the Earth at mid-infrared wavelengths (6 to 20 µm), where an advantageous contrast ratio between star and planet occurs. The baseline mission lasts 5 years and consists of approximately 200 individual target stars. Among these, 25 to 50 planetary systems can be studied spectroscopically, searching for gases such as CO 2 , H 2 O, CH 4 and O 3. Many of the key technologies required for the construction of Darwin have already been demonstrated and the remainder are estimated to be mature in the near future. Darwin is a mission that will ignite intense interest in both the research community and the wider public.

Antropología Filosófico-teológica tiene como objeto reflexionar sobre el ser humano y tiene cuatro campos que se corresponden con las intencionalidades que son: 

- Mostrar los orígenes y la realidad universo como el campo donde el ser humano estira y ahonda su raíz. El universo, y en él la tierra, que es anterior a todo viviente, constituye la patria y casa en la que la vida es. (Primera parte).

- Exponer las visiones de ser humano que van desde las filosofías orientales (Confucianismo, Hinduismo y Budismo), pasando brevemente por las visiones que se tienen en la filosofía griega (Sócrates, Platón y Aristóteles), en la filosofía patrística (Agustín de Hipona y Tomás de Aquino), en la filosofía moderna (Descartes y Kant), en la filosofía cristiana, hasta la visión del mismo en la en las historias y cosmovisiones en el Continente América. (Segunda parte).

- Explicitar al ser humano como un ser integral y pluridimensional que se hace en la historia y en el tiempo concretos. (Tercera parte).

- Presentar al Hombre Jesús de Nazareth quien a partir de su praxis y su proyecto liberador que tienen como objeto la construcción de un mundo justo y como destinatarios a los excluidos, se constituye en la revelación y panificación de la historia del ser humano en la historia del mundo y en la historia de Dios. (Cuarta parte).

Consciente de que ni el universo ni el ser humano están concluidos, este trabajo que trata de realidades inconclusas tampoco queda concluido, está abierto a toda crítica y aporte interdisciplinario.

Vicente Plasencia LLanos

Sumario 1. Raíces etimológicas y concepto de antropología 2. El lugar de la antropología en el concierto de las ciencias 3. Horizontes de la ciencia antropología 4. Teorías que explican el origen del universo y del ser humano 5. El recorrido de la pregunta del ser humano por el ser humano 6. Cuestiones antropológicas polémicas 7. Una aclaración al ¿por qué de una antropología personalista y cristiana? Introducción La antropología es una ciencia que nace con el ser humano pero que se ha sistematizado en los siglos XVII y XVIII y, sin embargo, sigue siendo una ciencia inacabada. Dicha ciencia tiene muchas acentuaciones y todas ellas convergen en las preguntas y respuestas que el ser humano se plantea para sí mismo tratando de comprender su identidad. En este horizonte, la pregunta que ha sido y es conductora de estas plurales y diferentes investigaciones es: ¿qué es el hombre?. Sin embargo, para responder a la cuestión del ser humano por el ser humano, son necesarios unos marcos conceptuales comunes que nos permitan contextualizar el fenómeno en cuestión, por eso, en este apartado trataré de presentar unas nociones generales de la ciencia objeto de estudio. Así entonces, empezaré por las raíces etimológicas y el esbozo de un posible concepto de la antropología; seguidamente pasaré a ver una contextualización científica de la ciencia antropología en el cosmos de las demás ciencias; continuaré con las teorías que explican el origen del ser humano; abordaré el recorrido de la pregunta conductora del tema macro y, con ella abriré la puerta hacia una antropología biológica, cultural y religiosa. Puesto que he sostenido que abriré la puerta hacia una antropología religiosa, quiero precisar que no estoy refiriéndome de ninguna manera a una visión necesariamente cristiana sino a esa actitud de apertura por parte de todo ser humano hacia la Trascendencia, experiencia humana que permitirá re-conocer algunos elementos que más tarde orientarán hacia la comprensión de una antropología que quiere ser de corte cristiana. (Ver Parte IV de este texto)

Here we argue that life emerged on Earth from a redox and pH front at c. 4.2 Ga. This front occurred where hot (c. 150 C), extremely reduced, alkaline, bisulphide-bearing, submarine seepage waters interfaced with the acid, warm (c. 90 C), iron-bearing Hadean ocean. The low pH of the ocean was imparted by the ten bars of CO 2 considered to dominate the Hadean atmosphere/hydrosphere. Disequilibrium between the two solutions was maintained by the spontaneous precipitation of a colloidal FeS membrane. Iron monosulphide bubbles comprising this membrane were inflated by the hydrothermal solution upon sulphide mounds at the seepage sites. Our hypothesis is that the FeS membrane, laced with nickel, acted as a semipermeable catalytic boundary between the two fluids, encouraging synthesis of organic anions by hydrogenation and carboxylation of hydrothermal organic primers. The ocean provided carbonate, phosphate, iron, nickel and protons; the hydrothermal solution was the source of ammonia, acetate, HS , H 2 and tungsten, as well as minor concentrations of organic sulphides and perhaps cyanide and acetaldehyde. The mean redox potential (Eh) across the membrane, with the energy to drive synthesis, would have approximated to 300 millivolts. The generation of organic anions would have led to an increase in osmotic pressure within the FeS bubbles. Thus osmotic pressure could take over from hydraulic pressure as the driving force for distension, budding and reproduction of the bubbles. Condensation of the organic molecules to polymers, particularly organic sulphides, was driven by pyrophosphate hydrolysis. Regeneration of pyrophosphate from the monophosphate in the membrane was facilitated by protons contributed from the Hadean ocean. This was the first use by a metabolizing system of protonmotive force (driven by natural pH) which also would have amounted to c. 300 millivolts. Protonmotive force is the universal energy transduction mechanism of life. Taken together with the redox potential across the membrane, the total electrochemical and chemical energy available for protometabolism amounted to a continuous supply at more than half a volt. The role of the iron sulphide membrane in keeping the two solutions separated was appropriated by the newly synthesized organic sulphide polymers. This organic takeover of the membrane material led to the miniaturization of the metabolizing system. Information systems to govern replication could have developed penecontemporaneously in this same milieu. But iron, sulphur and phosphate, inorganic components of earliest life, continued to be involved in metabolism.

All known cosmic and geological conditions and laws of chemistry and thermodynamics allow that complex organic matter could have formed spontaneously on pristine planet Earth about 4,000 mya. Simple gasses and minerals on the surface and in oceans of the early Earth reacted and were eventually organized in supramolecular aggregates and enveloped cells that evolved into primitive forms of life. Chemical evolution, which preceded all species of extant organisms, is a fact. In this review, we have concentrated on experimental and theoretical research published over the last two decades, which has added a wealth of new details and helped to close gaps in our previous understanding of this multifaceted field. Recent exciting progress in the molecular and genetic analyses of existing life, in particular microorganisms of ancient origin, even supports the possibility that a cellular, self-reproducing common ancestor might be assembled and resurrected in anaerobic cultures at some time in the future. Charles Darwin did not, and indeed, could not, address and specify the earliest phases of life which preceded the Origin of Species. However, in a famous letter, he sketched “a warm little pond with all sorts of… (chemicals, in which) …a protein was chemically formed.” We try to trace the impact of his charming clear-sighted metaphor up to the present time.

¿Qué es el hombre? es la pregunta en la que el ser humano se revela a sí mismo como un problema y, el intento de aproximarse a una respuesta “conduce a mantenerse en alerta en su proceso, históricamente contextualizado, de humanización”. En este texto el autor realiza un acercamiento al problema del ser humano desde una perspectiva filosófica y teológica, mostrándolo como parte del entramado del proceso de la evolución cósmica que, habiendo llegado hasta la consciencia y la libertad en la cima de la evolución, se humaniza de modo contextualizado y plural; este ser humano, en su complejidad constitutiva, es uno y pluridimensional y, su realización historizada se da en el despliegue de sus dimensiones corporeo-sexuada, mundano-historizada, racio-intelectiva, psico-afectiva, intersubjetiva/social, de libertad, ético-política y trascendente y; cuanto ser espiritual y trascendente, esto es perspectiva cristiana, encuentra su derrotero en la historia de Jesús de Nazareth quien desde la historia concreta traza el camino de emancipación y liberación desde las víctimas. El texto responde radicalmente a los diálogos inter-pluri-trans-disciplinares ejercidos en las cátedras del Área Razón y Fe de la Universidad Politécnica Salesiana-Ecuador. El autor deja abierto el desafío de reflexión sobre el “Ser humano: Un pro-yecto inconcluso”. (Tomado del original de la contratapa del texto)

In 1858, two naturalists, Charles Darwin and Alfred Russel Wallace, independently proposed natural selection as the basic mechanism responsible for the origin of new phenotypic variants and, ultimately, new species. A large body of evidence for this hypothesis was published in Darwin's Origin of Species one year later, the appearance of which provoked other leading scientists like August Weismann to adopt and amplify Darwin's perspective. Weismann's neo-Darwinian theory of evolution was further elaborated, most notably in a series of books by Theodosius Dobzhansky, Ernst Mayr, Julian Huxley and others. In this article we first summarize the history of life on Earth and provide recent evidence demonstrating that Darwin's dilemma (the apparent missing Precambrian record of life) has been resolved. Next, the historical development and structure of the "modern synthesis" is described within the context of the following topics: paleobiology and rates of evolution, mass extinctions and species selection, macroevolution and punctuated equilibrium, sexual reproduction and recombination, sexual selection and altruism, endosymbiosis and eukaryotic cell evolution, evolutionary developmental biology, phenotypic plasticity, epigenetic inheritance and molecular evolution, experimental bacterial evolution, and computer simulations (in silico evolution of digital organisms). In addition, we discuss the expansion of the modern synthesis, embracing all branches of scientific disciplines. It is concluded that the basic tenets of the synthetic theory have survived, but in modified form. These sub-theories require continued elaboration, particularly in light of molecular biology, to answer openended questions concerning the mechanisms of evolution in all five kingdoms of life. Dedicated to Prof. Dr. Dr. hc mult. Ernst Mayr on the occasion of his 100th birthday U. Kutschera ( ) )

Spectacular advances in structural and molecular biology have added support to the 'RNA world' hypothesis, and provide a mandate for chemistry to explain how RNA might have been generated prebiotically on the early earth. Difficulties in achieving a prebiotically plausible synthesis of RNA, however, have led many to ponder the question posed in the title of this paper. Herein, we review recent experimental work on the assembly of potential RNA precursors, focusing on methods for stereoselective C-C bond construction by aldolisation and related processes. This chemistry is presented in the context of a broader picture of the potential constitutional self-assembly of RNA. Finally, the relative accessibility of RNA and alternative nucleic acids is considered.

Mitochondria are essential organelles for cellular integrity and functionality maintenance and their imparement is implicated in the development of a wide range of diseases, including metabolic, cardiovascular, degenerative and hyperproliferative pathologies. The identification of different compounds able to interact with mitochondria for therapeutic purposes is currently becoming of primary importance. Indeed, it is well known that foods, particularly those of vegetable origin, present several constituents with beneficial effects on health. This review summarizes and updates the most recent findings concerning the mechanisms through which different dietary compounds from plant foods affect mitochondria functionality in healthy and pathological in vitro and in vivo models, paying particular attention to the pathways involved in mitochondrial biogenesis and apoptosis.

The Astrobiology Primer has been created as a reference tool for those who are interested in the interdisciplinary field of astrobiology. The field incorporates many diverse research endeavors, but it is our hope that this slim volume will present the reader with all he or she needs to know to become involved and to understand, at least at a fundamental level, the state of the art. Each section includes a brief overview of a topic and a short list of readable and important literature for those interested in deeper knowledge. Because of the great diversity of material, each section was written by a different author with a different expertise. Contributors, authors, and editors are listed at the beginning, along with a list of those chapters and sections for which they were responsible. We are deeply indebted to the NASA Astrobiology Institute (NAI), in particular to Estelle Dodson, David Morrison, Ed Goolish, Krisstina Wilmoth, and Rose Grymes for their continued enthusiasm and support. The Primer came about in large part because of NAI support for graduate student research, collaboration, and inclusion as well as direct funding. We have entitled the Primer version 1 in hope that it will be only the first in a series, whose future volumes will be produced every 3-5 years. This way we can insure that the Primer keeps up with the current state of research. We hope that it will be a great resource for anyone trying to stay abreast of an ever-changing field. If you have noticed any errors of fact or wish to be involved in future incarnations of the project, please contact Lucas Mix (e-mail: [email protected]).

Fourteen sesquiterpenes, three monoterpenes and one diterpene natural product have been isolated from the seeds of Artemisia annua. The possible biogenesis of some of these natural products are discussed by reference to recently reported experimental results for the autoxidation of dihydroartemisinic acid and other terpenoids from Artemisia annua. #

The NASA Astrobiology Roadmap provides guidance for research and technology development across the NASA enterprises that encompass the space, Earth, and biological sciences. The ongoing development of astrobiology roadmaps embodies the contributions of diverse scientists and technologists from government, universities, and private institutions. The Roadmap addresses three basic questions: how does life begin and evolve, does life exist elsewhere in the universe, and what is the future of life on Earth and beyond? Seven Science Goals outline the following key domains of investigation: understanding the nature and distribution of habitable environments in the universe, exploring for habitable environments and life in our own Solar System, understanding the emergence of life, determining how early life on Earth interacted and evolved with its changing environment, understanding the evolutionary mechanisms and environmental limits of life, determining the principles that will shape life in the future, and recognizing signatures of life on other worlds and on early Earth. For each of these goals, Science Objectives outline more specific high priority efforts for the next three to five years. These eighteen objectives are being integrated with NASA strategic planning. Astrobiology 8, xxx-xxx.

Understanding the origin of cellular life on Earth requires the discovery of plausible pathways for the transition from complex prebiotic chemistry to simple biology, defined as the emergence of chemical assemblies capable of Darwinian evolution. We have proposed that a simple primitive cell, or protocell, would consist of two key components: a protocell membrane that defines a spatially localized compartment, and an informational polymer that allows for the replication and inheritance of functional information. Recent studies of vesicles composed of fatty-acid membranes have shed considerable light on pathways for protocell growth and division, as well as means by which protocells could take up nutrients from their environment. Additional work with genetic polymers has provided insight into the potential for chemical genome replication and compatibility with membrane encapsulation. The integration of a dynamic fatty-acid compartment with robust, generalized genetic polymer replication would yield a laboratory model of a protocell with the potential for classical Darwinian biological evolution, and may help to evaluate potential pathways for the emergence of life on the early Earth. Here we discuss efforts to devise such an integrated protocell model.

P rebiotic soup experiments have shown that the molecular building blocks of life can be built under prebiotically plausible conditions. From this starting point, researchers have launched continued studies of polymerization and explorations of the breadth of RNA function. Recently, effort has intensified to examine experimentally another stage of the origins of life: the assembly of the molecular parts into model protocells intended to represent the first primitive, cell-like systems to emerge on Earth.

The first systems of molecules having the properties of the living state presumably self-assembled from a mixture of organic compounds available on the prebiotic Earth. To carry out the polymer synthesis characteristic of all forms of life, such systems would require one or more sources of energy to activate monomers to be incorporated into polymers. Possible sources of energy for this process include heat, light energy, chemical energy, and ionic potentials across membranes. These energy sources are explored here, with a particular focus on mechanisms by which self-assembled molecular aggregates could capture the energy and use it to form chemical bonds in polymers. Based on available evidence, a reasonable conjecture is that membranous vesicles were present on the prebiotic Earth and that systems of replicating and catalytic macromolecules could become encapsulated in the vesicles. In the laboratory, this can be modeled by encapsulated polymerases prepared as liposomes. By an appr...

All cells contain much more potassium, phosphate, and transition metals than modern (or reconstructed primeval) oceans, lakes, or rivers. Cells maintain ion gradients by using sophisticated, energydependent membrane enzymes (membrane pumps) that are embedded in elaborate ion-tight membranes. The first cells could possess neither ion-tight membranes nor membrane pumps, so the concentrations of small inorganic molecules and ions within protocells and in their environment would equilibrate. Hence, the ion composition of modern cells might reflect the inorganic ion composition of the habitats of protocells. We attempted to reconstruct the "hatcheries" of the first cells by combining geochemical analysis with phylogenomic scrutiny of the inorganic ion requirements of universal components of modern cells. These ubiquitous, and by inference primordial, proteins and functional systems show affinity to and functional requirement for K + , Zn 2+ , Mn 2+ , and phosphate. Thus, protocells must have evolved in habitats with a high K + /Na + ratio and relatively high concentrations of Zn, Mn, and phosphorous compounds. Geochemical reconstruction shows that the ionic composition conducive to the origin of cells could not have existed in marine settings but is compatible with emissions of vapor-dominated zones of inland geothermal systems. Under the anoxic, CO 2 -dominated primordial atmosphere, the chemistry of basins at geothermal fields would resemble the internal milieu of modern cells. The precellular stages of evolution might have transpired in shallow ponds of condensed and cooled geothermal vapor that were lined with porous silicate minerals mixed with metal sulfides and enriched in K + , Zn 2+ , and phosphorous compounds.

From anarchism to artificial intelligence and genetics to global terrorism, BEGINNER'S GUIDES equip readers with the tools to fully understand the most challenging and important debates of our age. Written by experts in a clear and accessible style, books in this series are substantial enough to be thorough but compact enough to be read by anyone wanting to know more about the world they live in. anarchism ruth kinna anti-capitalism simon tormey artificial intelligence blay whitby biodiversity john spicer bioterror & biowarfare malcolm dando the brain ammar al-chalabi, martin r. turner & r. shane delamont criminal psychology ray bull et al. democracy david beetham energy vaclav smil evolution burton s. guttman evolutionary psychology robin dunbar, louise barrett & john lycett fair trade jacqueline decarlo genetics anthony griffiths, burton guttman, david suzuki & tara cullis global terrorism leonard weinberg NATO jennifer medcalf the palestine-israeli conflict dan cohn-sherbok & dawoud el-alami philosophy of mind edward feser postmodernism kevin hart quantum physics alastair i.m. rae religion martin forward the small arms trade matt schroeder, rachel stohl & dan smith FORTHCOMING: astrobiology lewis dartnell asylum pamela goldberg beat generation christopher gair bioethics heather widdows capitalism andrew kilmister, gary browning cloning aaron levine conspiracy theories alasdair spark existentialism thomas wartenburg extrasolar planets ian stevens forensic science jay siegel galaxies joanne baker gender & sexuality samuel a. chambers globalization simon lee human rights david beetham immigration liza schuster mafia & organized crime james finckenauer political philosophy christopher bertram racism alana lentin radical philosophy andrew collier time amarendra swarup Contents Preface viii Illustrations xi 10 Life in the Universe Figure 2 The chirality of amino acids. Only the left-handed version is used by terrestrial life. 'R' here denotes the side group, of which 20 different kinds are used by natural proteins.

Evolution requires the genotype-phenotype distinction, a primeval epistemic cut that separates energy-degenerate, rate-independent genetic symbols from the rate-dependent dynamics of construction that they control. This symbolmatter or subject-object distinction occurs at all higher levels where symbols are related to a referent by an arbitrary code. The converse of control is measurement in which a rate-dependent dynamical state is coded into quiescent symbols. Non-integrable constraints are one necessary condition for bridging the epistemic cut by measurement, control, and coding. Additional properties of heteropolymer constraints are necessary for biological evolution.

In every organism, translation of the genetic information into functional proteins is performed on the ribosome. In Escherichia coli up to 40% of the cell's total energy turnover is channelled toward the ribosome and protein synthesis. Thus, elaborate networks of translation regulation pathways have evolved to modulate gene expression in response to growth rate and external factors, ranging from nutrient deprivation, to chemical (pH, ionic strength) and physical (temperature) fluctuations. Since the fundamental players involved in regulation of the different phases of translation have already been extensively reviewed elsewhere, this review focuses on lesser known and characterized factors that regulate the ribosome, ranging from processing, modification and assembly factors, unusual initiation and elongation factors, to a variety of stress response proteins.

[Pre-print of a paper published in Progress of Biophysics and Molecular Biology, September 2012]

]The fundamental problem posed by Darwin distinguishes his theory from any transformism of the past as well as any evolutionism to come: since variation is inherent to the living, it is a question of explaining, not at all why the living varies, but instead why the living does not vary in all directions to the point of constituting a continuum of forms varying ad infinitum. What limits and stabilizes this intrinsically unlimited variation, allowing certain forms to subsist and multiply to the detriment of others, is natural selection. This double principle of intrinsic variation/extrinsic selection constitutes a vector for the unification of reality that underlies Jean-Jacques Kupiec's ontophylogenesis as well as Deleuze and Guattari's global philosophy of Nature. Therefore, everything would potentially tend to incessantly vary. The work of Kupiec and others identifies an intrinsic random variation within ontogenesis itself. For Deleuze and Guattari, it is nothing but the figure, already selected by the organic stratum, of a more fundamental or pure variation. But, in fact, nothing really varies incessantly: everything undergoes a selective pressure according to which nothing subsists as such except what manages to endure through invariance (physical stratum) or reproduction (organic stratum). Thus, organic stratification only retains from variation what ensures and augments this reproduction. In this sense, every organism stratifies, i.e. submits to its imperative of subsistence and reproduction, a body without organs that varies in itself and always tends to escape the organism, for better (intensifications of life) or worse (cancerous pathologies).

Stable, hydrogen-burning, M dwarf stars comprise about 75% of all stars in the Galaxy. They are extremely long-lived and because they are much smaller in mass than the Sun (between 0.5 and 0.08 MSun), their temperature and stellar luminosity are low and peaked in the red. We have re-examined what is known at present about the potential for a terrestrial planet forming within, or migrating into, the classic liquid-surface-water habitable zone close to an M dwarf star. Observations of protoplanetary disks suggest that planet-building materials are common around M dwarfs, but N-body simulations differ in their estimations of the likelihood of potentially-habitable, wet planets residing within their habitable zones, which are only ~ 1/5 to 1/50 of the width of that for a G star. Particularly in light of the claimed detection of the planets with masses as small as 5.5 and 7.5 MEarth orbiting M stars, there seems no reason to exclude the possibility of terrestrial planets. Tidally locked synchronous rotation within the narrow habitable zone doesn't necessarily lead to atmospheric collapse, and active stellar flaring may not be as much of an evolutionarily disadvantageous factor as has previously been supposed. We conclude that M dwarf stars may indeed be viable hosts for planets on which the origin and evolution of life can occur. A number of planetary processes such as cessation of geothermal activity, or thermal and non-thermal atmospheric loss processes may limit the duration of planetary habitability to periods far shorter than the extreme lifetime of the M dwarf star. Nevertheless, it makes sense to include M dwarf stars in programs that seek to find habitable worlds and evidence of life.

During the Hadean to early Archean period (4.5-3.5 Ga), the surface of the Earth&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s crust was predominantly composed of basalt and komatiite lavas. The conditions imposed by the chemical composition of these rocks favoured the crystallization of Fe-Mg clays rather than that of Al-rich ones (montmorillonite). Fe-Mg clays were formed inside chemical microsystems through sea weathering or hydrothermal alteration, and for the most part, through post-magmatic processes. Indeed, at the end of the cooling stage, Fe-Mg clays precipitated directly from the residual liquid which concentrated in the voids remaining in the crystal framework of the mafic-ultramafic lavas. Nontronite-celadonite and chlorite-saponite covered all the solid surfaces (crystals, glass) and are associated with tiny pyroxene and apatite crystals forming the so-called &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;mesostasis&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;. The mesostasis was scattered in the lava body as micro-settings tens of micrometres wide. Thus, every square metre of basalt or komatiite rocks was punctuated by myriads of clay-rich patches, each of them potentially behaving as a single chemical reactor which could concentrate the organics diluted in the ocean water. Considering the high catalytic potentiality of clays, and particularly those of the Fe-rich ones (electron exchangers), it is probable that large parts of the surface of the young Earth participated in the synthesis of prebiotic molecules during the Hadean to early Archean period through innumerable clay-rich micro-settings in the massive parts and the altered surfaces of komatiite and basaltic lavas. This leads us to suggest that Fe,Mg-clays should be preferred to Al-rich ones (montmorillonite) to conduct experiments for the synthesis and the polymerisation of prebiotic molecules.

The continuity of abiotically formed bilayer membranes with similar structures in contemporary cellular life, and the requirement for microenvironments in which large and small molecules could be compartmentalized, support the idea that amphiphilic boundary structures contributed to the emergence of life. As an extension of this notion, we propose here a `Lipid World&#39; scenario as an early evolutionary step in

The phenomenon of pre-publication of research results is becoming common in some areas of science and several dedicated sites are available to authors who wish to establish priority for their data. The Editors of OLEB have become aware that an increasing fraction of manuscripts submitted to the journal have also been posted on web-sites such as arXiv or Nature Precedings prior to submission. While the desire of some authors to establish priority for their research results is understandable, the Editors of OLEB wish to discourage the abuse of this practice. We are thus establishing a clear policy regarding submission to the journal. Effective immediately, submitted manuscripts which are identical to online manuscripts will not be considered for publication. While the posting of a preliminary version of the manuscript will not necessarily disqualify it from being considered, the existence of a preposted version will be taken into account in evaluating whether or not the paper is suitable for submission, and submissions to OLEB should include links to or copies of previously posted versions of the material. Acceptability for submission assumes that manuscripts have not been submitted or published elsewhere in significantly duplicative form.

Replicators are fundamental to the origin of life and evolvability. Their survival depends on the accuracy of replication and the efficiency of growth relative to spontaneous decay. Infrabiological systems are built of two coupled autocatalytic systems, in contrast to minimal living systems that must comprise at least a metabolic subsystem, a hereditary subsystem and a boundary, serving respective functions. Some scenarios prefer to unite all these functions into one primordial system, as illustrated in the lipid world scenario, which is considered as a didactic example in detail. Experimentally produced chemical replicators grow parabolically owing to product inhibition. A selection consequence is survival of everybody. The chromatographized replicator model predicts that such replicators spreading on surfaces can be selected for higher replication rate because double strands are washed away slower than single strands from the surface. Analysis of real ribozymes suggests that the error threshold of replication is less severe by about one order of magnitude than thought previously. Surface-bound dynamics is predicted to play a crucial role also for exponential replicators: unlinked genes belonging to the same genome do not displace each other by competition, and efficient and accurate replicases can spread. The most efficient form of such useful population structure is encapsulation by reproducing vesicles. The stochastic corrector model shows how such a bag of genes can survive, and what the role of chromosome formation and intragenic recombination could be. Prebiotic and early evolution cannot be understood without the models of dynamics.

Dissolved H 2 concentrations up to the mM range and H 2 levels up to 9-58% by volume in the free gas phase are reported for groundwaters at sites in the Precambrian shields of Canada and Finland. Along with previously reported dissolved H 2 concentrations up to 7.4 mM for groundwaters from the Witwatersrand Basin, South Africa, these findings indicate that deep Precambrian Shield fracture waters contain some of the highest levels of dissolved H 2 ever reported and represent a potentially important energy-rich environment for subsurface microbial life. The ␦ 2 H isotope signatures of H 2 gas from Canada, Finland, and South Africa are consistent with a range of H 2 -producing water-rock reactions, depending on the geologic setting, which include both serpentinization and radiolysis. In Canada and Finland, several of the sites are in Archean greenstone belts characterized by ultramafic rocks that have undergone serpentinization and may be ancient analogues for serpentinite-hosted gases recently reported at the Lost City Hydrothermal Field and other hydrothermal seafloor deposits. The hydrogeologically isolated nature of these fracture-controlled groundwater systems provides a mechanism whereby the products of water-rock interaction accumulate over geologic timescales, which produces correlations between high H 2 levels, abiogenic hydrocarbon signatures, and the high salinities and highly altered ␦ 18 O and ␦ 2 H values of these groundwaters. A conceptual model is presented that demonstrates how periodic opening of fractures and resultant mixing control the distribution and supply of H 2 and support a microbial community of H 2 -utilizing sulfate reducers and methanogens.