Quote from Betapeg:
For anyone interested in what I am referring to when I say there is a pathway for abiogenesis and some of the steps have already been recreated in a laboratory, here is some of the experimental data I posted earlier in responding to jem's assertion that there is no proof of abiogenesis. Here it is. Undeniable evidence that a pathway exists in regards to abiogenesis. Scientists are still working on completing our understand of this process but what we have very much validates the fact of abiogenesis. Philosophical quotations and deceptive statistics are worthless against hard data such as this.
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An article in Discover Magazine points to research by the Miller group indicating the formation of seven different amino acids and 11 types of nucleobases in ice when ammonia and cyanide were left in a freezer from 1972â1997. This article also describes research by Christof Biebricher showing the formation of RNA molecules 400 bases long under freezing conditions using an RNA template, a single-strand chain of RNA that guides the formation of a new strand of RNA. As that new RNA strand grows, it adheres to the template.
http://discovermagazine.com/2008/fe...start:int=0&-C=
Levy, M.; Miller, S. L.; Brinton, K.; Bada, J. L. (June 2000). "Prebiotic synthesis of adenine and amino acids under Europa-like conditions". Icarus 145 (2): 609â13.
http://www.ingentaconnect.com/conte.../00005009#aff_1
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Evidence of the early appearance of life comes from the Isua supercrustal belt in Western Greenland and from similar formations in the nearby Akilia Islands. Carbon entering into rock formations has a ratio of Carbon-13 (13C) to Carbon-12 (12C) of about −5.5 (in units of δ13C), where because of a preferential biotic uptake of 12C, biomass has a δ13C of between −20 and −30. These isotopic fingerprints are preserved in the sediments, and Mojzis has used this technique to suggest that life existed on the planet already by 3.85 billion years ago.
Mojzis, S. J. et al. (1996). "Evidence for life on earth before 3,800 million years ago". Nature 384 (6604): 55â9.
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A graduate student, Stanley Miller, and his professor, Harold Urey, performed an experiment that demonstrated how organic molecules could have spontaneously formed from inorganic precursors, under conditions like those posited by the Oparin-Haldane Hypothesis. The now-famous "MillerâUrey experiment" used a highly reduced mixture of gasesâmethane, ammonia and hydrogenâto form basic organic monomers, such as amino acids.
Miller, Stanley L. (1953). "A Production of Amino Acids Under Possible Primitive Earth Conditions". Science 117 (3046): 528â9.
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Apart from the MillerâUrey experiment, the next most important step in research on prebiotic organic synthesis was the demonstration by Joan Oró that the nucleic acid purine base, adenine, was formed by heating aqueous ammonium cyanide solutions. In support of abiogenesis in eutectic ice, more recent work demonstrated the formation of s-triazines (alternative nucleobases), pyrimidines (including cytosine and uracil), and adenine from urea solutions subjected to freeze-thaw cycles under a reductive atmosphere (with spark discharges as an energy source).
Oró, J. (1961). "Mechanism of synthesis of adenine from hydrogen cyanide under possible primitive Earth conditions". Nature 191 (4794): 1193â4.
Menor-Salván C, Ruiz-Bermejo DM, Guzmán MI, Osuna-Esteban S, Veintemillas-Verdaguer S (2007). "Synthesis of pyrimidines and triazines in ice: implications for the prebiotic chemistry of nucleobases". Chemistry 15 (17): 4411â8.
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In the 1950s and 1960s, Sidney W. Fox studied the spontaneous formation of peptide structures under conditions that might plausibly have existed early in Earth's history. He demonstrated that amino acids could spontaneously form small peptides. These amino acids and small peptides could be encouraged to form closed spherical membranes, called proteinoid microspheres, which show many of the basic characteristics of 'life'.
http://nitro.biosci.arizona.edu/cou...fe/origins.html
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Geoffrey W. Hoffmann, a student of Eigen, contributed to the concept of life involving both replication and metabolism emerging from catalytic noise. His contributions included showing that an early sloppy translation machinery can be stable against an error catastrophe of the type that had been envisaged as problematical by Leslie Orgel ("Orgel's paradox") and calculations regarding the occurrence of a set of required catalytic activities together with the exclusion of catalytic activities that would be disruptive. This is called the stochastic theory of the origin of life.
Hoffmann, G. W. (1974). "On the Origin of the Genetic Code and the Stability of the Translation Apparatus". J. Mol. Biol. 86: pp. 349â362.
Orgel, L. (1963). "The Maintenance of the Accuracy of Protein Synthesis and its Relevance to Ageing". Proc. Nat. Acad. Sci. USA 49: pp. 517â521.
Hoffmann, G. W. (1975). "The Stochastic Theory of the Origin of Life". Annual Review of Physical Chemistry 26: pp. 123â144.
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While features of self-organization and self-replication are often considered the hallmark of living systems, there are many instances of abiotic molecules exhibiting such characteristics under proper conditions. For example Martin and Russel show that physical compartmentation by cell membranes from the environment and self-organization of self-contained redox reactions are the most conserved attributes of living things, and they argue therefore that inorganic matter with such attributes would be life's most likely last common ancestor.
Virus self-assembly within host cells has implications for the study of the origin of life, as it lends further credence to the hypothesis that life could have started as self-assembling organic molecules.
Martin, William; Russel, Michael J. (2003). "On the origins of cells: a hypothesis for the evolutionary transitions from abiotic geochemistry to chemoautotrophic prokaryotes, and from prokaryotes to nucleated cells". Phil. Trans. R. Soc. B 358 (1429): 59â83; discussion 83â5.
http://www.biology-direct.com/content/1//29
Vlassov AV, Kazakov SA, Johnston BH, Landweber LF (August 2005). "The RNA world on ice: a new scenario for the emergence of RNA information". J. Mol. Evol. 61 (2): 264â73.
http://www.sciencedirect.com/scienc...996e96f342023d3
read the last sentences.
In natural science, abiogenesis (pronounced /ˌeɪbaɪ.ɵˈdʒɛnɨsɪs/ ay-by-oh-jen-ə-siss) or biopoesis is the study of how biological life arises from inorganic matter through natural processes, and the method by which life on Earth arose. Most amino acids, often called "the building blocks of life", can form via natural chemical reactions unrelated to life, as demonstrated in the MillerâUrey experiment and similar experiments that involved simulating some of the conditions of the early Earth in a laboratory.[1] In all living things, these amino acids are organized into proteins, and the construction of these proteins is mediated by nucleic acids, that are themselves synthesized through biochemical pathways catalysed by proteins. Which of these organic molecules first arose and how they formed the first life is the focus of abiogenesis.
In any theory of abiogenesis, two aspects of life have to be accounted for: replication and metabolism. The question of which came first gave rise to different types of theories. In the beginning, metabolism-first theories (Oparin coacervate) were proposed, and only later thinking gave rise to the modern, replication-first approach.
In modern, still somewhat limited understanding, the first living things on Earth are thought to be single cell prokaryotes (which lack a cell nucleus), perhaps evolved from protobionts (organic molecules surrounded by a membrane-like structure).[2] The oldest ancient fossil microbe-like objects are dated to be 3.5 Ga (billion years old), approximately one billion years after the formation of the Earth itself.[3][4] By 2.4 Ga, the ratio of stable isotopes of carbon, iron and sulfur shows the action of living things on inorganic minerals and sediments[5][6] and molecular biomarkers indicate photosynthesis, demonstrating that life on Earth was widespread by this time.[7][8]
The sequence of chemical events that led to the first nucleic acids is not known. Several hypotheses about early life have been proposed, most notably the iron-sulfur world theory (metabolism without genetics) and the RNA world hypothesis (RNA life-forms).
http://en.wikipedia.org/wiki/Abiogenesis