This article is devoted to the origins of life from a scientific point of view. The mythical and religious aspects are treated in the article Cosmogonie. The preceding scientific theory of the origin of life is treated in the article spontaneous Generation .

The origins of life on Ground remain dubious. However, of many scientific theories exists to explain the appearance of the Vie, such as we know it today, which one thinks that it goes back to approximately 3,5 to 3,8 billion years.

This article treats events former to the appearance of the three great lines of alive the.

Appearance of the life

John Maynard Smith and Eörs Szathmáry defines eight major transitions from the evolution, of which three relate to the appearance of the life:

1. transition since molecules autoréplicantes towards a population from molecules in an isolated compartment;
2. passage of independent réplicateurs to the Chromosome S;
3. transition from a world to ARN - where the ARN plays the part of genome and enzyme - in a world with DNA and Protéine S.

John Desmond Bernal, as for him, suggests the three following stages:

1. appearance of organic monomers,
2. transitions towards organic polymers,
3. evolution since molecules towards the cell.

In fact, there does not exist “standard” model to describe the origin of life. However the model most usually accepted is founded on the supposed sequence of the following events:

1. Of the plausible prebiotic conditions involves the creation of simple organic molecules which are the building blocks of the alive one.
2. Of the Phospholipides spontaneously forms double-layers which are the basic structure of the cellular membranes.
3. the mechanisms which produce by chance molecules of ARN (ribonucleic acid), able to act like able ARN-enzymes, under certain very particular conditions, to duplicate itself. It is a first form of Génome, and we are then in the presence of protocellules.
4. the ARN-enzymes are gradually replaced by Protéine S Enzyme S, thanks to the appearance of the Ribozyme S, those being able to carry out the Synthèse of the proteins.
5. DNA appears and replaces the ARN in the role of support of the genome, in same time the ribozymes are supplemented by proteins, forming the Ribosome S. It is the appearance of the current organization of the living organisms.

Stages 2 and 3 are sometimes reversed, insulation in compartment being then presented after the appearance of the ARN autoréplicants.

The origin of the organic molecules

The oldest traces of organic molecules were found in 2006, in fossils of Crinoïde S. Âgés of 350 million years, it acts of made up being connected with Pigment S, discovered by Christina O' Malley and his/her colleagues of the Université of Ohio.

An explanation: condensation on mineral surfaces

The assembly of small molecules (like the amino-acids) in macromolecules (as proteins) requires the elimination of molecules of Eau. However, thermodynamics indicates that it is unfavourable to carry out such a condensation in water itself. It is possible to solve this contradiction to call upon mineral surfaces, like the Argile S or the Pyrite S. the Adsorption of the small molecules on these surfaces concentrates them and modifies them chemically, which can make the formation of macromolecules more favorable.

Clay, for example, is very abundantly on Earth and consists of a stacking of fine layers. Between the various beds of the clay can slip certain small organic molecules, which allows an important adsorption. Clay is also a very effective catalyst for many organic reactions, and could thus have allowed the polymerization of the amino-acids and/or the nucleic acids. The English chemist Cairns-Smith developed this assumption in Seven clues to the origin off life in 1985 (French translation: the enigma of the life , 1990).

The Urey-Miller experiment and the origin of the organic molecules

In 1953, Stanley Miller, accompanied by Harold Urey, wanted to reproduce the conditions of the primitive Ground. They locked up in a balloon of the gases (CH₄ methane, NH₃ ammonia, Hydrogène H₂ and Eau H₂O) and subjected the mixture to electric shocks during seven Jour S.

They obtained organic molecules, bricks of alive, and in particular of the Urée (IDIOT ₂H ₄), Formaldéhyde (H ₂CO), Hydrocyanic acid (HCN), bases and amino-acid (AA). Some compounds being present at more than 2%.

Miller and Urey used a reducing atmosphere (Méthane CH₄, NH₃, H₂, H₂O) such as it was on Earth at the time of the appearance of the life and not an oxidizing atmosphere. Since the experiment several times were remade, by varying the composition of the atmosphere and the energy source (use of the radiation Ultraviolet in particular). However, the oxidizing atmosphere (Carbon dioxide CO₂, Azote N₂, water H₂O) which comes from the volcanicity gives very bad outputs.

Exploitation of the idea of Miller

Following the experiments of Miller, it was necessary to determine the chemical reactions which occurred in the enclosure (the balloon in which it had locked up various gases). Thus Organic chemistry in water was born the .

These reactions require strong concentrations, fields of Température and very narrow pH which makes that these mechanisms are far from probable: a pond in process of draining could perhaps explain strong the concentration S.

The experiment at the time was very criticized because of that. Moreover, its reliability was called into question because the organic molecules obtained could a priori come from an external contamination. An external contamination does not hold however the road for the reasons evoked hereafter.

Asymmetry of the biomolécules

The chiral molecules “” are molecules being able to exist in two possible forms: laevogyrous ( left ) and dextrogyre ( right ), in the same way that the left hand and the right hand are the symmetrical image one of the other. One calls enantiomer S these various forms.

A thorough analysis of the molecules obtained in the experiment of Miller shows that one obtains a racemic Mélange of molecules (as many right forms than of left ), whereas one knows since the middle of the 19th century (in particular with work of Pasteur in 1847) that the natural amino-acids exist practically only under one of their two forms enantiomers (one speaks then about homochirality): the laevogyrous form.

One however found traces of amino-acids of dextrogyre in free form, in peptides or even of proteins. These forms, not very frequent, would have physiological functions in addition. In the alive world, one notes however that sugars present in DNA are only of dextrogyre type, or that the agents of savor have a different taste according to their form.

Theories on the origin of the homochirality

There exist two main categories of theories explaining the homochirality: the biotic theories and the abiotic theories .

In the first, one postulates that the life would have appeared starting from a mixture of enantiomers, and that the homochirality would have appeared only gradually during the evolution. According to Laurent Nahon, this type of theory is not however much any more constant, owing to the fact that it was discovered that the Protéine S cannot be folded up correctly if the amino-acids which compose them are not chiral. One would thus estimate that the homochirality would be rather former to the appearance of the life, they are the abiotic theories.

Crystals and enantiomers

The properties of the crystals make it possible to imagine a scenario: certain inorganic crystals expose faces having an intrinsic chirality, like calcite or quartz. These faces could adsorb preferentially one of the two forms enantiomer S and thus selectively concentrate it at the expense of the other. However, nothing indicates that the crystals could play a part in the formation of organic molecules.

Asymetricity and thermodynamics

It was discovered that the matter is intrinsically asymmetrical. “When one places Atome S of Cobalt in an asymmetrical geometry, i.e. in magnetic fields, the electron S product decay of Neutron always move in the direction opposed to their Spin (aligned at once). The electrons are thus intrinsically left. ” This experiment of Tsung CAD Lee and Chen Ning Yang which accepted the Nobel Prize in 1957 can be reproduced with any atom. A Gaz of vapor of Césium for example in a electromagnetic Champ has an optical activity. It is it on which Marie-Anne Bouchiat worked, research director CNRS with the ENS. This phenomenon is easily observable on the heavy atoms because the concerned force is the weak force of interaction between the core and the electron.

Thus it was calculated that the natural amino-acids are thermodynamically more stable than their image in a mirror.

Formation of enantiomers in space

In the years 1970, amino-acids were discovered in the Météorite of Murchison, but, they were present mainly in their laevogyrous form. 70 different amino-acids were thus discovered, of which 3 only belong to the 20 natural amino-acids. The exact percentage of laevogyrous molecules is however much discussed, because of possible contaminations, and varies between 50% and -5% following the research teams.

The idea that the homochirality would originate in of the molecules come from the space is thus developed.

The enantiomers absorb the Lumière differently when this one is polarized “circularly” right or left . However, these molecules are degraded after absorption, thus leading to an excess of an enantiomeric form.

It was discovered, in 1997, that the Nébuleuse of Orion produces polarized light circular with 17% in the Infrarouge (IR). The infra-red does not have enough energy to break covalent bonds, but one can suppose that the Ultraviolet S (UV) are also circularly polarized.

An experiment undertaken in 2005 by Uwe Meierhenrich and its colleagues, showed that a racemic mixture of a simple amino-acid, irradiated by a radiation UV led to a homochiral mixture. In this experiment, the Leucine is used in a solid state, reproducing the space conditions. After an irradiation by a radiation circularly polarized Synchrotron right (near the wavelength observed in space, in remote UV), the experiment makes it possible to obtain an excess of the laevogyrous enantiomer of 2.6%.

However, it is enough to an excess of 1% in reactions which discuss to lead to a homochiral mixture of 100%. According to Laurent Nahon, no experiment related to concurrent theories arrived to such an excess.

Organic molecules with the protocellules

Today, of many models solve the problem of the appearance of the organic molecules. The scientists manage to produce many small biological molecules (amino-acid, nucleic sugars, bases) under prebiotic conditions in laboratories.

The experiments of Miller and the models which of it are derived do not provide an explanation on the following stages which include the transition from the monomers to the biopolymères, then to the protocellules and finally to the alive cells having a Métabolisme basic. Also the scientists explored other ways of research.

Isolated compartments

The appearance of compartments isolated by a membrane poses serious problems. The membranes of the alive cells are made up of Lipide S, but one knows today fatty-acids with long chain which can spontaneously form small spherical membranes . Although one can produce such compartments in laboratories, these fatty-acids remain synthesized by enzymes. The process making it possible to form such compartments in the absence of these enzymes remains unknown.

Protocellules

A compartment isolated by a membrane does not form however a protocellule. According to Maynard Smith, two conditions are necessary to form true a protocellule:

1. the molecules able to retort the base form (the replicator S ) must bind between them of a “Chromosome”, thus forming a structural unit, guaranteeing to the réplicateurs to form a coherent whole after the replication;
2. the membrane must have mechanisms of exchange with the external medium, others that the current systems with proteins.

Appearance of the genome

Models “genes initially”

In this model, the appearance of the genome preceded the appearance of the metabolism. Molecules of DNA or ARN would have thus existed only, being autorépliquant starting from the molecules present in their environment. The “individuals” are thus represented by the nucleic acid molecules of themselves.

Models “metabolism initially”

Several models reject the idea of the autoreplication of a “naked” Gène and make the assumption of the appearance of a primitive Métabolisme which would have preceded emergence by the replication of the ARN. One of the first versions of this assumption was presented in 1924 by Alexander Oparin with its idea of primitive blisters able to be retorted, at one time when one did not know yet the structure of the DNA.

Other alternatives appeared in the Eighties and Nineties like the theory of Günter Wächtershäuser on a world thio-ferrous ore, or the models of Christian de Duve based on the chemistry of the Thioester S.

Other more abstract arguments were also presented. One can quote the mathematical model of Freeman Dyson with the beginning of the year 1980 on the probability of the emergence of a metabolism without presence of genes, or work of Stuart Kauffman on the overall autocatalytic units (see spontaneous Generation for a presentation of the ideas of Kauffman on the origin of life).

Metabolism and genome: a world with ARN

The assumption of the world with Ribonucleic acid (ARN) is that the ARN was the principal one - and undoubtedly only - form of life before the emergence of the first cell with DNA. It is Walter Gilbert which used for the first time the term “world with ARN” (“RNA world” in English) in 1986.

The assumption of a world with ARN has the favor of the scientists today and is founded on several elements. In particular on the fact that the ARN is in theory able as well to ensure of the metabolic tasks as to be the support of information Génétique.

Storage and replication

The ARN with the capacity to store information, by using a genetic Code similar to that of the DNA. The ARN can also behave like a Ribozyme (of the contraction of ribose and enzyme ) and to catalyze certain reactions, just like the proteins. From the point of view of the reproduction, this molecule thus has two paramount functions: the information storage and catalysis necessary to the autoreplication.

The DNA can also recopy itself, but only with the protein assistance. The proteins are very good catalysts but they are unable to store information necessary for their own replication. The ARN is him able at the same time of catalysis and autoreplication. Thus, the Ribosome is a ribozyme, in the direction where the person in charge of the synthesis of proteins is not a protein (as it is the case in the large majority of the catalyzes of an alive cell) but ribosomal ARN itself. These ribozymes can be folded up in space, revealing an active site for a catalysis, following the example proteins.

The DNA, forming a double rigid helix, cannot be folded up to play a part of catalyst.

Effectiveness of proteins

The Protéine S are very effective catalysts, much more than the ribozymes. In the same way, there exist 20 amino-acid in the alive world, but only four nucleotides, the proteins thus are diversified much than the ARN.

From an evolutionary point of view, it is thus not very probable that an protein-enzyme was replaced by an ARN-enzyme. Contrary, if the ARN appeared well before proteins, it is plausible that they were replaced by proteins, more effective.

This argument is supported by the fact that the ARN plays a part in the synthesis of proteins, via its fundamental role in current ribosomes. The ARN would thus to some extent have led to the appearance of proteins.

The proteins, used in the structure of ribosome, would thus have come later, in order to improve the system. The first proteins would thus have been selected from their activity improving operation of the ribozymes, for finally replacing them.

A phylogenetic large distribution

The ARN are present in the three lines of the alive world (Archée S, Procaryote S, Eucaryote S). They achieve in each one a great number of different tasks, most known are ARN messenger (ARNm, conveying information Génétique of DNA towards ribosomes), ARN of transfer (ARNt, establishing the link between Nucleic acid and Amino-acid) and ribosomal ARN (ARNr, component structural and functional of the Ribosome S). Beside those, one can find a great number of ARN implied in functions such as catalyzes, regulations of the gene expression, controls, viral defenses anti , extinctions of Gène S, inhibitions of protein syntheses, restorations genomic, etc It is the case of interfering ARN S (ARNs), whose certain researchers qualify the mechanism of “universal”. The ARNtm of the procaryotes, also have several functions: they play at the same time the parts of ARN of transfer and ARN messenger.

It is interesting to note that in spite of this great structural and functional diversity, the distribution of the ARN makes it possible to find the cutting of the alive one. Thus, small nucleolar ARN S is divided only by archées and the eucaryotes, the ARN of the télomérase is him present only at the eucaryotes whereas the procaryotes are the only ones to have of ARNtm. In the same way, the three great types of ARN (ARNt, ARNm and ARNr) are present in the three lines.

The case of the ARN of transfer

The role of ARNt is to transport an amino-acid towards ribosome, where the connection with another amino-acid will be carried out, to form a polypeptide (thus giving a protein). There exists several ARNt, having each one three nucleotides: the anticodon. The anticodon corresponds to a Codon, carried by ARNm which defines the order of assembly of the amino-acids by ribosome.

The characteristic of ARNt that it is, in spite of its small size, partly consists of many Nucléotide S which one does not meet elsewhere. These “exotic” nucleotides would have a prebiotic origin thus, vestiges of a world with ARN. One thus finds these components in all three field of the alive one.

Virus and ARNt

It is relatively frequent to observe Virus with ARN or Viroïde S carrying of the reasons similar to ARNt. Thus, in the viroïde PSTV ( Potato Spindle To tube Viroïd ) and ARNt of the Tyrosin, one finds the same reasons structural in “clover sheet”. For Marie-Christine Maurel, “the latter play a fundamental role in the alive one and their seniority is not a doubt”.

Another surprising structure: at virus TYMV ( Turnip Yellow Mosaic Virus ), the starter of the translation of the genome of the protein virus is done by the means of a structure of the ARNt type which starts its own translation and which fixes an amino-acid.

Directed evolution of ARN

In 1990, Larry Gold and Jack Szostak developed a method aiming at directing the evolution of ARN, in order to select those showing a catalytic activity. They since succeeded in obtaining ribozymes able to bind nucleotides between them, to bind amino-acids to of ARNs, to carry out reactions of Oxydo-réduction S, to bind to components of the membrane, etc

It is thus in possible theory, on this model, that the ARN alone is enough to establish a primitive metabolism. However, it still remains to discover a ARN able to retort itself.

ARN and heredity

The ARN plays a part in the transmission of the activity of genes: such a mechanism (qualified epigenetic ) is not related to the DNA, and would be a proof of the capacity of the ARN to be taken part in the Hérédité.

At the origin of the DNA in the cell

From the point of view of the cellular Biology, the DNA is produced by modification of a ARN: the Désoxyribonucléotide S (precursors of the DNA) are indeed produced starting from the Ribonucléotide S (precursors of the ARN). Moreover, the grouping Thymine (identified like T in the genetic Code), is built starting from a grouping Uracile (U). However, although uracil is specific to the ARN and the thymine with the DNA, the grouping U is, at the time of the synthesis, already fixed on a désoxyribonucléotide.

ARN with the DNA

On the assumption of the world with ARN, appear first of all Viroïde S resembling ARN autocatalytic, present in isolated compartments (which they are membrane or crystalline). Then protocellules, capable of antiquated metabolism, are subjected to an evolution Darwin ienne, thus evolving/moving worms of the cells with ARN, able to present a varied and complex activity.

Ribozymes or proteins?

Although the ARN is thus at the origin of the DNA in the cellular metabolism, this reaction is very difficult to realize. In fact, in the three lines, it is catalyzed by specialized proteins: the ribonucléotides-réductases. Moreover, this reaction is very expensive in energy, because of reduction of the Ribose, and it produces free radical , very reagents, on protein. The ARN being a fragile molecule, it appears improbable that it can support free radicals without the protein intervention.

Thus, the origin of the DNA finds probably its source after the appearance of proteins, essential to each stage of its synthesis starting from precursors of the type ARN, within the cell.

Interest of the DNA

The DNA presents a certain number of advantages on the ARN, in term of conservation of the integrity of genetic information.

First of all it breaks less easily, because the Désoxyribose of the DNA contains a Atome Oxygène of less than the ribose of the ARN. However the Oxygène can easily interact on the connections between Nucléotide S, posing a problem of stability then.

Then, the DNA allows the repair of a recurring problem: the transformation of the grouping Thymine (T) into uracil (U). Indeed, uracil is only present in the ARN, they are an anomaly in the DNA.

Selective advantage of the DNA: the assumption of the virus

The advantages in terms of stability of the DNA could not be enough to explain its adoption. Thus, Patrick Forterre advances the assumption that an additional selective advantage can be due to the conflicts between Virus and alive cells.

In this model, the first organization with DNA would be a virus. The DNA would confer on the virus the capacity to resist Enzyme S degrading the genomes ARN, arms with probable defense of the cells. One finds the same principle at current viruses, which deteriorate their DNA to resist enzymes produced by Bactérie S infected.

Currently, one can observe that the enzymes necessary to the translation of the ARN towards the DNA are very present at the Rétrovirus, whose genome is carried by ARN. In the same way, of many viruses their own enzymes of synthesis of the DNA code.

This assumption is also corroborated by the discovery of virus to DNA, of which this one contains, not groupings thymines, but of the groupings uracils. From the evolutionary point of view, there thus would have been initially appearance of the désoxyribonucléotides, then of the DNA with uracil (ADN-U), then of DNA with thymine (ADN-T), which would have gradually been essential. According to Patrick Forterre, it is even probable that the ADN-T “was invented twice”, at different viruses.

The viruses with ARN would be here relics of the world with ARN, the viruses with ADN-U would be then relics of the world having preceded that with ADN-T.

Viruses, first organizations with DNA

The viruses with DNA could be older than the first cell with DNA: the first cell with DNA would thus have borrowed it from one or more virus, under the pressure of an arms race (Théorie of the red queen).

Didier Raoult and Jean-Michel Claverie thus discovered the Mimivirus: a giant virus with DNA (its genome being twice longer than the smallest known bacterial genome). The characteristic of this virus is that it can produce proteins implied in the translation of the protein ARN (like enzymes charging with the amino-acids on of ARNt), it could thus have for ancestors of the viruses older than the first cell with DNA.

Eugene Koonin and his colleagues proposed, by comparing genomes sequences, that the majority of the enzymes implied in the replication of the DNA are different between the procaryotes and the eucaryotes (accompanied by archées). They conclude from it that the DNA would have been invented independently in the line of the procaryotes and that leading to the eucaryotes and to archées.

In the same way, the enzymes of réplications of the viruses with DNA are very different from one virus to another, like compared to the cellular enzymes playing the same part.

These indices let think that the enzymes related to the DNA appeared during a “first age” of the world with DNA, where existed cells with ARN and virus with ARN and DNA.

Passage de l'ADN in the cells

The nature of the genome of the most former ancestor common to all the living beings (than the scientists prénomment LUCA) remains unknown: did it still make part of the world with ARN, or had it already a genome with DNA? At all events, LUCA is the fruit of a long evolution. The genome of the first cells, which preceded LUCA, was undoubtedly consisted molecules of ARN and not of DNA. Contrary to the DNA, the ARN can indeed play at the same time the part of enzyme and genetic material. Stanley Miller and Christian de Duve think that the appearance of the ARN was itself a late event, indeed, this molecule does not seem to be able to be synthesized by the simple methods of prebiotic chemistry. The ARN would thus have been preceded by molecules of which we will undoubtedly know never true nature.

What leads the scientists to think that the ARN preceded the DNA results from this report: the three great lines of alive share only the system of synthesis of proteins, whereas they differ on the system from replication from the DNA.

There then exist several assumptions for the passage of the DNA (of origin viral) in the alive cells: either this passage occurred only once, or it could take place several times, independently in the various lines. In the first case, the first genes of the enzymes of réplications would thus have been replaced thereafter by those of another virus, thus forming the three lines.

The assumption of Patrick Forterre is that the three lines of alive find their sources in the replacement of the genome with ARN by the genome with DNA of three different viruses. One finds in particular here the assumption of a viral origin of the core of the eucaryotes.

Work of Carl Woese seems to support this assumption, by showing that the speed of evolution of proteins seems to have fallen at the time of the appearance of the three lines. This reduction would be due to the passage of the ARN with the DNA, the genomes with DNA being more stable, and thus less sensitive to the change S.

In this scenario, the appearance of three lines only is explained by the fact that the cells with DNA supplanted the cells with ARN little by little, thus preventing the appearance of new lines per passage ARN→ADN.

Other models

Hydrothermal sources: the world of sulfur

The hydrothermal sources were discovered in 1977 to 2600 meters of depth, where two tectonic plates separate.

The hydrothermal mounts are located on the sedimentary Couche. Their diameter at the base varies from 25 to 100 meters and their height varies from 70 to 100 meters. The chimneys of these smokers are sometimes covered with a crust of Oxyde of manganese. The smokers located on these mounts are composed of a friable solid whose color varies black gray with ocher, they are sulfides of iron, Cuivre and Zinc.

These sources are particularly interesting because one found the life there where it was believed impossible: private medium of oxygen, at high temperature, charged with metals and sulfur, in the most total darkness. However gradients of temperature important around these zones and fact that the Ultraviolet S destructors do not arrive so deeply (whereas they destroy any molecule formed on the surface) are good conditions for the appearance of the life.

These organizations have the same forms as those which one knows more close to surface (DNA, Protéine S, Sucre S…) but draw their energy of oxidation to transform the mineral carbon into Organic matter.

In addition, of the experiments were carried out, at the laboratory of geophysics of Washington, and showed that under the conditions which exist around the vents, there is formation of, reduced form of the Azote which is so much necessary to the formation of the organic molecules of the first part and which did not exist in the oxidizing atmosphere. The hydrothermal sources are thus of good sources of.

A primitive extraterrestrial origin (exogenèse)

An alternative assumption is that the life was initially formed out of the Ground. The organic compounds are relatively frequent in space, in particular in the remote zones of the solar system where the evaporation of the volatile compounds is very reduced. Some Comet S are coated in layers with dark matter, which one thinks of being a kind of Bitume formed by a combination of simple carbonaceous compounds and ultraviolet rays. The cometary material rain on the primitive Earth could have brought complex quantities of molecules organic, which would have caused the appearance of the life on Earth.

A broader assumption is the Panspermie: the life even would have appeared in space then disseminated on Earth. According to an alternative, the life would have appeared on Mars initially and of the impacts of comets and asteroids on Mars would have projected material of Martian surface on Earth. It is even more difficult to find indices to justify these assumptions than the more traditional theories.

These theories of an origin Extraterrestre do not explain directly how the life appeared, because they make a priori only defer the problem. However, they widen the conditions under which the life could appear in the universe. Perhaps the future samples of brought back grounds of Mars and comets will make it possible to obtain new brief replies.

Topicality On the planet Mars, terrestrial Spore S of Bactérie S were discovered, which proves in experiments the theoretical possibility of the transport of life in space. -->

External bonds

• To easily include/understand the origin of life on the Earth
• a site which explains with simple words the origins of life
• the three great theories of the appearance of the life on Earth

See too

• cellular Biology
• Exobiologie
• Habitability of a planet
• spontaneous Generation
• Protéinoïde

Sources

• John Desmond Bernal, The origin off life , Weidenfeld editions & Nicolson, 1967.
• Guillemette Lauters, Olivier Lenaerts, Daniel Rousselet and Eric Depiereux, Bioscope: The origin of life .
• John Maynard Smith, Eörs Szathmáry, the Origins of life , Dunod editions, 2000. ISBN 2100048600
• J. William Schopf, Anatoliy B. Kudryavtsev, David G. Agresti, Thomas J. Wdowiak, Andrew D. Czaja, “Laser−Raman imagery off Earth' S earliest fossils”, in Natural , volume 416, pages 73-76, March 2002.
• Marie-Christine Maurel, Birth of the life: prebiotic evolution with the biological evolution , Dunod editions, 2003 (3rd edition). ISBN 2100068822
• NR. Fujii, T. Saito, “Homochirality and life”, in The Chemical Records , volume 4,5, pages 267-78, 2004
• Uwe J. Meierhenrich, a step towards the origin of the homochirality… , November 2005.
• Patrick Forterre, “the origin of the genome”, in files of Research: history of the life, great stages of the evolution , 19, pages 34-40, May 2005.
• Marc-Andre Selosse, “Which relationship enters the three great lines of the alive one? ”, in files of Research: history of the life, great stages of the evolution , 19, pages 42-45, May 2005.
• “Laurent Nahon: “The asymmetry of the biomolécules comes from space””, remarks collected by Franck Daninos, in Research , 390, October 2005.
• U. Meierhenrich, L. Nahon, C. Alcaraz, J. Bredehöft, S. Hoffmann, B. Barber, A. Brack, “Asymmetric VUV photodecomposition off the amino acid D, It in the solid state”, in Angewandte Chemie International Edition , volume 44, pages 5630-5634, July 2005.

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