by Laurence D Smart B.Sc.Agr., Dip.Ed., Grad.Dip.Ed
[Free to print and distribute. Copy must be in full.]
The Time-Span for Pre-Biology
(1) The amount of time available for life to begin is getting shorter, making abiogenesis more impossible.
(2) Higher levels of carbon-12 in carbon chemicals extracted from rocks 3.8 billion years old is evidence that photosynthesis has been around for almost 4 billion years (by the evolutionary timescale). [Nature, Vol. 333, p:313-318 1988]
(3) "The finding of algal filaments dated at only slightly more than 1 billion years younger than the earth itself restricted the time required for the evolution of the living cell." [S. Aw, CEN Tech. J., Vol. 10, No. 3, p:302 1996, (see Nature, Vol. 284, p:441-443 1980; Nature, Vol. 284, p:443-445 1980; Nature, Vol. 291, p:218-220 1981; & Nature, Vol. 319, p:489-491 1986)]
(4) "The probability of forming the 2,000 or so enzymes needed by a cell lies in the realm of 1 in 1040,000. This makes the conceptual leap from even the most complex 'soup' to the simplest cell in the time available (that is about 500 million years) so dramatic that it requires some suspension of rationality in order to accept it." [S. Aw, CEN Tech. J., Vol. 10, No. 3, p:303 1996, (see Fred Hoyle, "The Intelligent Universe", Michael Joseph: London, p:16 1983)]
(5) "The time available for the origin of the cell has shrunk to one tenth or less than has been assumed." [S. Aw, CEN Tech. J., Vol. 10, No. 3, p:311 1996]
Urey & Miller's Simulation
(1) The 'proof' is still not proof.
(2) "Keep in mind, however, that there are valid scientific objections to this scenario as well as to the several others that have been seriously entertained so that we are far from certain as to how life arose." [D & J Voet, "Biochemistry", John Wiley and Sons: New York, p:21 1995]
(3) "Since then, workers have subjected many different mixtures of simple gases to various energy sources. The results of these experiments can be summarized neatly. Under sufficiently reducing conditions, amino acids form easily. Conversely, under oxidizing conditions, they do not arise at all or do so only in small amounts." [L.E. Orgel, Scientific American, Vol. 271, No. 4, p:56 1994]
(4) "Doubt has arisen because recent investigations indicate the earth's atmosphere was never as reducing as Urey & Miller presumed." [L.E. Orgel, Scientific American, Vol. 271, No. 4, p:53-61 1994]
(1) New experimental results cast doubt on the current DNA theory of life.
(2) "All this just means that hypotheses of the origin of the genetic code based on our understanding of the nature of the DNA, its transcription and translation have to be substantially revised." [S. Aw, CEN Tech. J., Vol. 10, No. 3, p:308 1996]
(1) DNA correlations are showing fewer relationships than first promoted.
(2) The C-Value Paradox is now apparent - There is no consistent correlation between the amount of DNA an organism has and its level of complexity. [H. Lodish, et al, "Molecular Cell Biology" (3rd ed.), Scientific American Books: (Dist. W.H. Freeman & Co.): New York, p:312 1995]
[S. Aw, CEN Tech. J., Vol. 10, No. 3, p:306 1996]
(1) Junk DNA does not explain the C-Value Paradox.
(2) Some scientists regard the idea that there is 'junk' or 'useless' DNA as untenable. [Science, Vol. 263, p:608-610 1994]
(3) "In addition there are hints of a language structure, akin to that seen with ordinary languages, in the lengths of non-protein coding DNA. Their findings support the possibility that non-coding regions of DNA may carry biological information." [S. Aw, CEN Tech. J., Vol. 10, No. 3, p:308 1996, (see Physical Review Letters, Vol. 73, p:3169-3172)]
(4) "What is increasingly seen as the DNA story unfolds is prima facie evidence of intelligent design extending over the whole molecule." [S. Aw, CEN Tech. J., Vol. 10, No. 3, p:308 1996 ]
(1) RNA looks less likely to have led to the evolution of life.
(2) RNA is more reactive than DNA, making DNA the most likely progenitor of life. [CEN Tech. J., Vol. 10, No. 3, p:304 1996]
(3) "The most reasonable interpretation is that life did not start with RNA ... The transition to an RNA world, like the origins of life in general, is fraught with uncertainty and is plagued by a lack of relevant experimental data. Researchers into the origins of life have grown accustomed to the level of frustration in these problems" [Nature, Vol. 338, p:222,223 1989]
(4) "The prebiotic production of numerous isomers and closely related molecules hinders the likelihood of forming desirable mononucleosides. Furthermore, unless ribose and the purine bases form nucleosides rapidly they would be degraded quite quickly." [S. Aw, CEN Tech. J., Vol. 10, No. 3, p:303-304 1996]
(1) The change of cells from an anaerobic world to aerobic has not been solved.
(2) "This enzyme [in E. coli] poses a conundrum: the survival and continual evolution of an oxygen-sensitive enzyme when oxygen appeared. On the other hand, the class I reductase require oxygen for free radical generation. Surely they could not have evolved and operated in the anaerobic first cell in an oxygen-free environment." [Science, Vol. 260, p:1773-1777 1993]
(1) The origins of life at thermal vents is still only speculation.
(2) "The high temperatures in the vents would not allow synthesis of organic compounds, but would decompose them, unless the exposure time at vent temperatures was short. Even if the essential organic molecules were available in the hot hydrothermal waters, the subsequent events of polymerization and the conversion of these polymers into the first organisms would not occur as the vent waters were quenched to the colder temperatures of the primitive oceans." [S.L. Miller and J.L. Bada, Nature, Vol. 334, p:609-611 1988]
Homochirality (Right & Left-Handed Molecule Dominance)
(1) Experiments have not shown why there is an almost total dominance of one chiral form (left-handedness) in earth's life forms.
VIZ. - dextro (d) sugars & levo (l) amino acids
(2) "The logical conclusion from these considerations is a simple and parsimonious one, that homochirality and life came together. But evolutionary lore forbids such a notion. It claims to explain how life began, but on the profound issues of life's 'handedness' there is no selective mechanism that it can plausibly endorse." [S. Aw, CEN Tech. J., Vol. 10, No. 3, p:309 1996 ]
(1) Life originating from the Archaebacteria cannot be proven by protein comparisons.
(2) "However, using protein phylogeny to root the tree of life is not safe; besides the possibility of lateral gene transfer, one cannot be sure that proteins compared in an individual [evolutionary] tree descended from a single gene in the common ancestor, or from already duplicated genes." [P. Forterre, et al, in "The Archaebacteria: Biochemistry and Biotechnology" (M.J. Danson, et al, eds.), Biochemical Soc. Symposium No. 58, Portland Press: London, p:99-112 1992]
A 'Balanced' Conclusion
(1) Life has not been proven to have been a result of abiogenesis.
(2) "So it is disappointing, but not surprising, that the origin of the genetic code is still as obscure as the origin of life itself." [Nature, Vol. 367, p:111 1994]
SOURCE: CEN Tech. J., Vol. 10, No. 3, p:300-314 1996