Other Problems In The Current Origin Theories

A common and pervasive criticism of the work done in this field is that far too many life origin experiments take great liberties with assumptions about conditions present on the early earth and show little concern for problems of investigator interference (such as the common use of purified reagents in these experiments, which is highly questionable at best). The processes used to demonstrate abiogenesis must be simple and robust ones which could have taken place under undirected conditions with the kinds of natural, racemic (random) and impure mixtures that could have existed on the early earth (these types of mixtures are virtually never used in lab experiments). This simplicity is required - or the relevance of the experiment to any true abiogenesis is moot. Another significant example of these liberties would include the source and origin of available organics for pre-biotic materials. cell_1.JPG (13588 bytes)  
As I have previously noted, many astronomers and geologists have pointed out that the early earth almost certainly never possessed a strongly reducing atmosphere as assumed in the Miller experiments. The early earth would have had an atmosphere similar to that of Mars and Venus - our two nearest neighbor planets - in that it would have been near neutral. The Miller method of producing amino acids and other organics simply does not work with near neutral gas mixtures. Yet variations on the Miller experiments continue to be published and presented unquestioningly in textbooks and journals. In fact, the best evidence Miller himself can offer for an early reducing atmosphere is the presence of life itself - that the organics for pre-biotic synthesis must have come from somewhere. As I have noted, others suggest meteorites may have been the source of the organics, citing a single meteorite that fell in Australia in 1969, which contained 100 PPM of organics which were similar in make up to those produced in the Miller-type experiments. What is rarely mentioned is that these carbonaceous meteorites are very rare, with the vast majority of meteorites having either and Iron or silicate based make up (this is why the 1969 Murchison meteorite is nearly always used as the only example). Even considering that meteorites fell at a far more frequent rate in the past, the rarity of carbonaceous types, their very low (<100 PPM) organics content as well as the fact that then, as now, only larger meteors make it through our atmosphere without burning up, have led many scientists, including Stanley Miller, to conclude that meteorites simply could not have been large contributors of organics to the early earth. The same sort of criticism can be offered for materials such as Hydrogen Cyanide thought to have come into our atmosphere from comets. So if we cannot identify how large quantities of organics might have come to be present, why should we then just assume their existence and move on to the issue of formation of more complex pre-biotic organics? Another difficult issue that is often glossed over without significant consideration is the issue of  random D and L amino acid mixtures (often referred to as left and right oriented forms). All natural processes (including the Miller-type)  produce random mixtures of both types. Yet all life forms use proteins which are made almost exclusively of the Left-handed variety - how these could be sorted out under pre-biotic conditions remains to be answered. Another little considered problem is the scarcity of soluble phosphorous, since phosphates tend to precipitate out as Calcium Phosphate, a common inorganic mineral. Phosphates are needed for both RNA and DNA synthesis in concentrations far greater than those commonly seen in any natural bodies of water.

A possible solution to a number of concerns which is often tossed out by many scientists, has been the thought that various mineral surfaces, such as clays, could provide significant abilities to collect, sort out and catalyze various desirable organic reactions. Unfortunately, under actual test conditions, minerals provide only the most meager assistance, and then only in a few types of reactions. Along similar lines, hot vents on the ocean bottom (including some known as "black smokers") are suggested by some as the focal points for the origin of life, providing heat to create reactions and sulfides that could be used as a "food" source. But researchers like Stanley Miller have pointed out that the vents do not make organic compounds, they destroy them. If these vents were as common on the early earth as some suggest, essentially all ocean waters would by cycled through them in geologically "short" periods of time, greatly limiting the amount of complex organic "soup" that could possibly build up in pre-biotic oceans. Although most researchers hold that life must have evolved through an "RNA World" stage during its initial development (because there is no explanation for sub-life complexity without some form of self-reproduction) they do so without any direct evidence. Many of the optimistic students of this science assume it must have happened - in spite of the fact that all the considerable research conducted to date fails to indicate any circumstance under which the RNA World might be possible. On top of this, without a self-replicating system, the RNA World theories are a moot proposal - they could not have accomplished anything. Yet  something is required to explain the complexity of pre-biotic building blocks - this seemingly purposeful and organized complexity cannot be simply glossed over or ignored.


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Conclusions About the Origins of Life
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