Origin of Life

Theories and evidence for chemical biopoieses

Astrobiology

Chemical evolution and the origin of life. : "During the last three decades major advances have been made in our understanding of the formation of carbon compounds in the universe and of the occurence of processes of chemical evolution. 1) Carbon and other biogenic elements (C,H,N,O,S and P) are some of the most abundant in the universe. 2) The interstellar medium has been found to contain a diversity of molecules of these elements. 3) Some of these molecules have also been found in comets which are considered the most primordial bodies of the solar system. 4) The atmospheres of the outer planets and their satellites, for example, Titan, are actively involved in the formation of organic compounds which are the precursors of biochemical molecules. 5) Some of these biochemical molecules, such as amino acids, purines and pyrimidines, have been found in carbonaceous chondrites. 6) Laboratory experiments have shown that most of the monomers and oligomers necessary for life can be synthesized under hypothesized but plausible primitive Earth conditions from compounds found in the above cosmic bodies. 7) It appears that the primitive Earth had the necessary and sufficient conditions to allow the chemical synthesis of biomacromolecules and to permit the processes required for the emergence of life on our planet. 8) It is unlikely that the emergence of life occurred in any other body of the solar system, although the examination of the Jovian satellite Europa may provide important clues about the constraints of this evolutionary process. Some of the fundamental principles of chemical evolution are briefly discussed."
Oro J. Chemical evolution and the origin of life. Adv Space Res. 1983;3(9):77-94.

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The universe: a cryogenic habitat for microbial life.

Entrez PubMed: "Panspermia, an ancient idea, posits that microbial life is ubiquitous in the Universe. After several decades of almost irrational rejection, panspermia is at last coming to be regarded as a serious contender for the beginnings of life on our planet. Astronomical data is shown to be consistent with the widespread distribution of complex organic molecules and dust particles that may have a biological provenance. A minuscule (10(-21)) survival rate of freeze-dried bacteria in space is all that is needed to ensure the continual re-cycling of cosmic microbial life in the galaxy. Evidence that terrestrial life may have come from elsewhere in the solar system has accumulated over the past decade. Mars is seen by some as a possible source of terrestrial life, but some hundreds of billions of comets that enveloped the entire solar system, are a far more likely primordial reservoir of life. Comets would then have seeded Earth, Mars, and indeed all other habitable planetary bodies in the inner regions of the solar system. The implications of this point of view, which was developed in conjunction with the late Sir Fred Hoyle since the 1970s, are now becoming amenable to direct empirical test by studies of pristine organic material in the stratosphere. The ancient theory of panspermia may be on the verge of vindication, in which case the entire universe would be a grand crucible of cryomicrobiology."

Wickramasinghe C. The universe: a cryogenic habitat for microbial life. Cryobiology. 2004 Apr;48(2):113-25.

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Possible steps to the emergence of life: the [GADV]-protein world hypothesis.

Possible steps to the emergence of life: the [GADV]-protein world hypothesis.: "Possible steps to the emergence of life: the [GADV]-protein world hypothesis.
Chem Rec. 2005; 5(2):107-18 (ISSN: 1527-8999)
Ikehara K
Department of Chemistry, Faculty of Science, Nara Women's University, Kita-uoya-nishi-machi, Nara, Nara 630-8506, Japan. ikehara@cc.nara-wu.ac.jp

Based on the fact that RNA has not only a genetic function but also a catalytic function, the RNA world theory on the origin of life was first proposed about 20 years ago. The theory assumes that RNA was amplified by self-replication to increase RNA diversity on the primitive earth. Since then, the theory has been widely accepted as the most likely explanation for the emergence of life. In contrast, we reached another hypothesis, the [GADV]-protein world hypothesis, which is based on pseudo-replication of [GADV]-proteins. We reached this hypothesis during studies on the origins of genes and the genetic code, where [G], [A], [D], and [V] refer to Gly, Ala, Asp, and Val, respectively. In this review, possible steps to the emergence of life are discussed from the standpoint of the [GADV]-protein world hypothesis, comparing it in parallel with the RNA world theory. It is also shown that [GADV]-peptides, which were produced by repeated dry-heating cycles and by solid phase peptide synthesis, have catalytic activities, hydrolyzing peptide bonds in a natural protein, bovine serum albumin. These experimental results support the [GADV]-protein world hypothesis for the origin of life."

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Metabolic Life Theory

Extremophiles 2002 -- Rossi et al. 185 (13): 3683 -- The Journal of Bacteriology: "most molecules with essential biological functions, such as nucleotides, some amino acids, and nucleic acids, are thermolabile. Miller's 'primitive soup' hypothesis, implying that the first living organisms used RNA as the information molecule, has been challenged by the 'metabolic life ' theory. This hypothesis suggests that primordial 'life' was nothing other than a series of self-catalyzed reactions based on simple compounds such as CO2 and CO. Since many reactions are thermodynamically more favorable at high temperatures, it has been suggested that hydrothermal environments were the cradle of this 'metabolic life.' "

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