Origin of life: Difference between revisions
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Because we must look backward to a time nearly four billion years ago, we will find little, but not nothing,<ref name=hazen>Hazen RM. (2005) Genesis: The Scientific Quest for Life's Origin. Washington,DC: Joseph Henry Press. ISBN 0309094321</ref> in the way of remains to examine. We can hypothesize, and submit those hypotheses to existing knowledge of earth's early conditions and to experiments attempting to reproduce those conditions. We can narrow our hypotheses and search-paths by dissecting out the most basic and essential physico-chemical processes common to all known living things — the universal biophysics,<ref name=schneider05> Schneider ED, Sagan D (2005) ''Into the Cool: Energy Flow, Thermodynamics, and Life.'' Chicago: The University of Chicago Press. ISBN 0-226-73937-6 [http://www.intothecool.com/ Chapter Excerpts and Reviews]</ref> biochemistry<ref name=pacepnas>[http://www.pnas.org/cgi/content/full/98/3/805 The universal nature of biochemistry, by Norman R. Pace]</ref> and metabolism<ref>Smith E., Morowitz HJ. (2004) Universality in intermediary metabolism. Proc Natl Acad Sci U S A 101:13168-13173. PMID 15340153 [http://dx.doi.org/10.1073/pnas.0404922101 Full-Text]</ref> of living things — because as conserved core processes they have the greatest probability of embryonic status. | Because we must look backward to a time nearly four billion years ago, we will find little, but not nothing,<ref name=hazen>Hazen RM. (2005) Genesis: The Scientific Quest for Life's Origin. Washington,DC: Joseph Henry Press. ISBN 0309094321</ref> in the way of remains to examine. We can hypothesize, and submit those hypotheses to existing knowledge of earth's early conditions and to experiments attempting to reproduce those conditions. We can narrow our hypotheses and search-paths by dissecting out the most basic and essential physico-chemical processes common to all known living things — the universal biophysics,<ref name=schneider05> Schneider ED, Sagan D (2005) ''Into the Cool: Energy Flow, Thermodynamics, and Life.'' Chicago: The University of Chicago Press. ISBN 0-226-73937-6 [http://www.intothecool.com/ Chapter Excerpts and Reviews]</ref> biochemistry<ref name=pacepnas>[http://www.pnas.org/cgi/content/full/98/3/805 The universal nature of biochemistry, by Norman R. Pace]</ref> and metabolism<ref>Smith E., Morowitz HJ. (2004) Universality in intermediary metabolism. Proc Natl Acad Sci U S A 101:13168-13173. PMID 15340153 [http://dx.doi.org/10.1073/pnas.0404922101 Full-Text]</ref> of living things — because as conserved core processes they have the greatest probability of embryonic status. | ||
We search for the origin of a system we recognize as living in virtue that it has the informational content and information-processing ability to remain as a compartmentalized near-steady-state self-organized dynamical system of hierarchical robust modular molecular networks, where the networks operate autonomously in their own behalf, to offset responses to perturbations, adapt to changing conditions, and facilitate the system's reproducing itself. We search for the origin of a system enabled by influx of energy and matter and by a more than compensatory efflux of waste (disorder), which thereby permits sustaining and exploiting a dynamically organized state far from the equilibrium state of randomness. Finally, we search for the origin of a system capable, through its self-reproductive ability, of participating in the evolutionary processes<ref name=jablonkalamb>Jablonka E, Lamb MJ (2005) ''Evolution in Four Dimension: Genetic, Epigenetic, Behavioral, and Symbolic Variation in the History of Life.'' Cambridge: The MIT Press</ref> that enable transgenerational evolution of the species to which it belongs, adapting to changing environments. | We search for the origin of a system we recognize as living in virtue that it has the informational content and information-processing ability to remain as a spatially compartmentalized near-steady-state self-organized dynamical system of hierarchical robust modular molecular networks, where the networks operate autonomously in their own behalf, to offset responses to perturbations, adapt to changing conditions, and facilitate the system's reproducing itself. We search for the origin of a system enabled by influx of energy and matter and by a more than compensatory efflux of waste (disorder), which thereby permits sustaining and exploiting a dynamically organized state far from the equilibrium state of randomness. Finally, we search for the origin of a system capable, through its self-reproductive ability, of participating in the evolutionary processes<ref name=jablonkalamb>Jablonka E, Lamb MJ (2005) ''Evolution in Four Dimension: Genetic, Epigenetic, Behavioral, and Symbolic Variation in the History of Life.'' Cambridge: The MIT Press</ref> that enable transgenerational evolution of the species to which it belongs, adapting to changing environments. | ||
Scientists do not know the origin of life on Earth. They do have pieces of the puzzle, however, and many conflicting plausible scientific scenarios. | Scientists do not know the origin of life on Earth. They do have pieces of the puzzle, however, and many conflicting plausible scientific scenarios. | ||
Revision as of 15:55, 1 June 2007
In a scientific context, in order to discuss, much less discover, the origin of life, we must first answer the question, "What is Life?" We can pose that question more coherently by asking, "What essential processes underpin the activity of living?" Knowing the fundamental physico-chemical processes that underpin the activity of all living systems gives us a starting point for making observations, generating hypotheses, and performing experiments in the search for life’s origin — for those processes somehow must have given rise to the earliest cells, the basic building blocks and working units of all living things on Earth. We must discover the characteristics of the earliest cells from which all current living things descended.
Because we must look backward to a time nearly four billion years ago, we will find little, but not nothing,[1] in the way of remains to examine. We can hypothesize, and submit those hypotheses to existing knowledge of earth's early conditions and to experiments attempting to reproduce those conditions. We can narrow our hypotheses and search-paths by dissecting out the most basic and essential physico-chemical processes common to all known living things — the universal biophysics,[2] biochemistry[3] and metabolism[4] of living things — because as conserved core processes they have the greatest probability of embryonic status.
We search for the origin of a system we recognize as living in virtue that it has the informational content and information-processing ability to remain as a spatially compartmentalized near-steady-state self-organized dynamical system of hierarchical robust modular molecular networks, where the networks operate autonomously in their own behalf, to offset responses to perturbations, adapt to changing conditions, and facilitate the system's reproducing itself. We search for the origin of a system enabled by influx of energy and matter and by a more than compensatory efflux of waste (disorder), which thereby permits sustaining and exploiting a dynamically organized state far from the equilibrium state of randomness. Finally, we search for the origin of a system capable, through its self-reproductive ability, of participating in the evolutionary processes[5] that enable transgenerational evolution of the species to which it belongs, adapting to changing environments.
Scientists do not know the origin of life on Earth. They do have pieces of the puzzle, however, and many conflicting plausible scientific scenarios.
The history of scientific 'origins' thinking
Origin of planet Earth and its pre-biotic characteristics
Pre-biotic chemical evolution
Pre-biotic chemical evolution as prelude to origin of living systems. See, for example:
The first replicators
Sources of energy
Community metabolism
Coding for amino acids
The RNA World
Rampant horizontal gene transfer hypothesis
RNA to DNA transition
Emergence of Darwinian struggle
Emergence of cells
Oldest fossils
References
Citations
- ↑ Hazen RM. (2005) Genesis: The Scientific Quest for Life's Origin. Washington,DC: Joseph Henry Press. ISBN 0309094321
- ↑ Schneider ED, Sagan D (2005) Into the Cool: Energy Flow, Thermodynamics, and Life. Chicago: The University of Chicago Press. ISBN 0-226-73937-6 Chapter Excerpts and Reviews
- ↑ The universal nature of biochemistry, by Norman R. Pace
- ↑ Smith E., Morowitz HJ. (2004) Universality in intermediary metabolism. Proc Natl Acad Sci U S A 101:13168-13173. PMID 15340153 Full-Text
- ↑ Jablonka E, Lamb MJ (2005) Evolution in Four Dimension: Genetic, Epigenetic, Behavioral, and Symbolic Variation in the History of Life. Cambridge: The MIT Press
- ↑ Dyson F (1982) A model for the origin of life. See Dyson (1982) J Mol Evol 18:344-350
- ↑ Post RL. (1990) The origin of homeostasis in the early earth. Journal of Molecular Evolution 31:257-64 Summary and Link to Full-Text.
- ↑ Galimov EM. (2004) Phenomenon of life: between equilibrium and non-linearity. Orig.Life Evol Biosph. 34:599-613.
- ↑ Danchin A, Fang G, Noria S. (2007) The extant core bacterial proteome is an archive of the origin of life. Proteomics 7:875-889 PMID 17370266
- ↑ Sayer RM. (2006) Self-organizing proto-replicators and the origin of life. Biosystems PMID 17014952
- ↑ Deamer D, Singaram S, Rajamani S, Kompanichenko V, Guggenheim S. (2006) Self-assembly processes in the prebiotic environment. Philos Trans R Soc Lond B Biol Sci 61:1809-1818 PMID 17008220
- ↑ Szathmary E. (2006) The origin of replicators and reproducers. Philos Trans R Soc Lond B Biol Sci 361:1761-1776 PMID 17008217
- ↑ Davies P. The FIFTH MIRACLE: The Search for the Origin and Meaning of Life (Paperback) Simon & Schuster ISBN-10: 068486309X ISBN-13: 978-0684863092
- ↑ Koonin EV. An RNA-making reactor for the origin of life. PNAS 2007;104:9105-6
- ↑ Baaske P, Weinert FM, Duhr S, Lemke KH, Russell MJ, Braun D. Extreme accumulation of nucleotides in simulated hydrothermal pore systems. PNAS 2007;104:9346-51.
External links
Further reading
- Goldenfeld N Woese C (2007) Essays: Connections. Biology's next revolution The emerging picture of microbes as gene–swapping collectives demands a revision of such concepts as organism, species and evolution itself. Nature 445:369 (25 January 2007) doi:10.1038/445369a
- Forterre P (2006) Three RNA cells for ribosomal lineages and three DNA viruses to replicate their genomes: A hypothesis for the origin of cellular domain PNAS 103:3669-3674
- Davies P. (2000) The Fifth Miracle: Search for the Origin and Meaning of Life. Simon & Schuster ISBN 978-0684863092
- From The New York Times Book Review, by Lee Smolin: "If you are going to read only one book on the origin of life, seriously consider this one. From Scientific American: "His thesis is that 'the first terrestrial organisms lived deep underground, entombed within geothermally heated rocks in pressure-cooker conditions.' Davies also looks at the theories that life began by chemical assembly in a watery medium and that it came to the earth from space in the form of already viable microbes--the panspermia hypothesis.