Emergence of life

8 Thordarson, R, Emergence of Life , in Encyclopedia of Supramolecular Chemistry, Atwood, J. L. and Steed, 

Modern life forms are based on DNA which is located within the cell nucleus and only self-replicates with the aid of enzymes that are synthesised based on instructions coded into the DNA and mediated by RNA. There is thns a chicken and egg paradox - which came first the DNA or the enzymes  

Theories for even earlier forms of mutateable transmission of genetic information have involved clay minerals. Montmorillonite clay particles have been demonstrated to catalyse the condensation of nucleotides and we discussed in Section 8.2.8 the Cairns-Smith hypothesis of how crystal dislocations could transmit some form of genetic information. Most hypotheses abont clays have yet to be demonstrated experimentally, however. 

Among the hot debate between theories concerning either a gradnal change from RNA self-replication to RNA-coded protein synthesis as in the RNA-world, or a merger of systems involving co-evolved RNA and catalytic peptides, another type of molecule - lipids - have until recently been overlooked. 

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Origin science a group which deals with processes which are non-recurring, such as the formation of the universe, historical events, the composition of a symphony, or the emergence of life. 

In 1963, Armin Weiss (then at the University of Heidelberg, Germany) reported the intercalation of amino acids and proteins in mica sheet silicates (Weiss, 1963). Some years later, U. Hoffmann, also from Heidelberg, published an article titled Die Chemie der Tonmineralien (The Chemistry of Clay Minerals), in which he mentioned possible catalytic activity of clays in processes which could have led to the emergence of life (Hoffmann, 1968). 

One important question is that of the order in which the basic mechanisms of evolution processes, leading eventually to the emergence of life, occurred. As far as the development of the genetic code is concerned, it is not clear whether the code evolved prior to the aminoacylation process, i.e., whether aminoacyl-tRNA synthetases evolved before or after the code. A tRNA species which is aminoacy-lated by two different synthetases was studied if this tRNA had important identity elements such as the discriminator base and the three anticodon bases for the two synthetases, this would be evidence that the aminoacyl-tRNA synthetases had developed after the genetic code. Dieter Soil s group, which is experienced in working with this family of enzymes, came to the conclusion that the universal genetic code must have developed before the evolution of the aminoacylation system (Hohn et al, 2006). 

The interpenetration of these phenomena, mediated by HGT, is also likely to be of great importance for evolution. According to the authors, the genetic code, which plays a key role in all forms of life, leads to the prediction that the first steps of the process of the emergence of life evolved in a Lamarckian manner, with vertical descent driven back by powerful early forms of HGT. 

Weber, B.H. (1998). Emergence of life and biological selection from the perspective of complex systems dynamics. In Van de Vigver et al. (eds.). Evolutionary Systems. Kluwer Academic Publishers, pp. 59-66... 

The period of emergence of life on Earth is constrained to be between the period 4.0-3.7 Gyr ago, for which there is no fossil record. Urey postulated that all of the planets formed from the same solar nebula and so the early Earth should have an atmosphere with a composition the same as that of Jupiter (known at the time),... 

Fry I. 1999. The Emergence of Life on Earth. Free Association Books London. 

Figure 1.1 An arbitrary scale of complexity towards the emergence of life.

Given the suitable initial conditions, the emergence of life is highly probable and governed by the laws of chemistry and physics... 

The hypothesis of an original emergence of life from inanimate matter. .. can at least offer the advantage of explaining natural things by natural pathways, thus avoiding the invocation of miracles, which are actually in contradiction with the foundations of science. 

Figure 2.2 The spontaneous self-aggregation of membranogenic surfactants into a vesicle, with an interior water pool that can host water-soluble molecules. If this self-aggregation takes place also in the presence of hydrophobic molecules, and/or ionic molecules, these can organize themselves into the bilayer or on the surface of the vesicle. A realistic scenario of the emergence of life can be based on a gradual transition from random mixtures of simple organic molecules to spatially ordered assemblies, displaying primitive forms of cellular compartmentation, selfreproduction, and catalysis.

You have extracted the nucleus from an oocyte. You have a nucleus and the rest of the cell. Neither of these two components is alive. Now you insert again the nucleus into the cell - or, in this respect - into a different enucleated cell (as in the cloning experiments). You get a living cell. Can this be taken as a demonstration for the emergence of life, to namely that hfe can be generated out of non-living components ... 

Luisi, P. L. (2006). The Emergence of Life From Chemical Origins to Synthetic Biology. Cambridge University Press. 

The value of the theory is to be assessed exclusively by its capacity for experimental test. Model experiments give quantitative standards by means of which the probability of each stage in the emergence of life may be estimated. 

Delsemme, A. (1998) Our Cosmic Origins from the Big Bang to the Emergence of Life and Intelligence, Cambridge University Press, Cambridge, p. 322. 

Figure 12.24 Proposed timescale for the emergence of life along with methodological approaches to its understanding according to Lahav.40...

The structure of energy makes the emergence of life inevitable if the proper reaction conditions prevail. This, the determinist s clarion always sounds true because its score is chiseled into the structure of energy manifest in atoms. It also is a useful sound for it tells us that, if we should learn how to get to another earthlike planet, our test for life should be based upon the very principles that led to life on this planet. 

Archer DG, Wang P (1990) The dielectric constant of water and Debye-Hiickel limiting law slopes. J Phys Chem Ref Data 19 371-411 Arrhenius G, Lepland A (2000) Accretion of Moon and Earth and the emergence of life. Chem Geol 169 69-82... 

Russell, M.J., and Hall, A.J. (1997) The emergence of life from iron monosulfide bubbles at a submarine hydrothermal redox and pH front. J. Geol. Soc. London 154, 377 102. 

That s the only way to get a lot of carbon out of the star and into space. But supernovas can t be too common or else they would destroy too many worlds. On the other hand, as I mentioned before, supernovas are important because the shock waves they produce can cause planetary systems to start to coalesce from dust clouds surrounding other stars. This means that there can t be too many supernovas or too few. Any substantial deviation would decrease planetary formation and the emergence of life. ... 

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