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Bad Science, Worse Philosophy: the Quackery and Logic-Chopping of David Foster's The Philosophical Scientists (2000)

 

Addendum C: The First Life

Richard Carrier

 

The following material was updated in 2006, in light of the publication of Richard Carrier's article, "The Argument from Biogenesis: Probabilities against a Natural Origin of Life," Biology & Philosophy 19.5 (November, 2004), pp. 739-64. An important discussion and clarification of that article appears below.

 

The current scientific view of the origin of life holds that DNA was a late development in the tree of life, and that probably some form of RNA-based life, or something similar, preceded it. For a good, near-current example of what we know, see the summary by Schwartz.[1] Schwartz writes that, based on protein-sequence analysis alone, it is clear that "all life on earth is descended from a single common ancestor," and "that ancestor...was certainly not the first form of life. It is probable that another, unseen phylogenetic tree preceded the one we can now reconstruct, and led from the first form of life to the progenote" (p. 325). Schwartz notes a few important facts that are significant about this. For instance, "in contrast to the multiple enzyme systems needed to carry out DNA replication, RNA replication can be performed by a single enzyme" (p. 326).

Schwartz then describes an experiment where random RNA replication produced observable evolution in the lab. A population of molecules which were vulnerable to hydrolytic reagents, when immersed in those reagents and allowed to replicate at random, evolved into a population of molecules which were not only invulnerable to the once-poisonous environment, but were dependent upon it for survival (p. 327). He also describes the Nobel-prize-winning work of Cech and Altman, who discovered catalytic RNA, a form of RNA capable of replicating on its own without assisting enzymes.[2] Although Schwartz did not provide enough information for me to be certain, this RNA molecule, called the tetrahymena, appears to have had a specificity well within the realm of the probable. However, this only shows that this sort of thing is possible. It is not yet known whether the tetrahymena was the basis of earth's protobiology, but something like it could have been.

There is more to be said about the actual biology of life's origins. Ian Musgrave and John Stockwell have set up two Probability of Abiogenesis FAQs which deeply challenge creationist notions of the improbability of life, and many of the points I make in my review of Foster are indirectly supported by arguments and material presented there.

In addition to the above, I've published an article that systematically outlines seven presently-fatal flaws in creationist arguments against a natural origin of life: Richard Carrier, "The Argument from Biogenesis: Probabilities against a Natural Origin of Life," Biology & Philosophy 19.5 (November, 2004), pp. 739-64. One clarification to this may be needed:

In that paper I state that Cech, et al., had "discovered catalytic RNA, a form of RNA capable of replicating on its own without any assisting enzymes" and "this chemical, the tetrahymena rhybozime, isn't necessarily the basis of earth life, but it proves that extremely simple replicators are possible" (p. 757). This statement may be misleading, though it wasn't meant to be. The tetrahymena's natural binding and splicing activity can produce a copy of any arbitrary RNA template of a limited size, though with much less efficiency than more evolved replication systems. So it can theoretically accomplish a primitive replication of another RNA strand, including replication of other tetrahymena RNA sequences, and therefore the tetrahymena is in that sense is self-replicating, since no other coded proteins would be needed for one tetrahymena to use another tetrahymena to make many additional tetrahymena.[3] Of course, this means the tetrahymena would only count as a possible self-replicator if life had begun with at least two of them in the same place and time. But this distinction does not matter for how I employed the example there, since I made no claims regarding the specific probability or complexity even of one tetrahymena molecule, much less two of them.

Certainly, this distinction between direct self-replication and self-replication using a pre-existing copy would affect any probability calculation that a critic of "biogenesis-by-tetrahymena" would want to carry out. But as I explain in that article, since other self-replicating systems that are even simpler have already been discovered, that avenue of criticism, even if it could be pursued--following all seven requirements for a successful argument articulated in my paper--is now moot. As I already note there, the lucky formation of a couple of tetrahymena molecules isn't necessarily how life got started. There are many other possibilities. For example, Gerald Joyce from Scripps and David Bartel from MIT are working on different ribozymes that can directly copy themselves and yet are smaller than the tetrahymena.[4]


[1] Alan W. Schwartz, "Biology and Theory: RNA and the Origin of Life," in The Chemistry of Life's Origins, edited by J.M. Greenberg, et al. (1993): pp. 323-44.

[2] See: B.L. Bass and T.R. Cech, "Specific Interaction Between Self-Splicing of RNA of Tetrahymena and Its Guanosine Substrate," in Nature 308 (1984), p. 820; T.R. Cech, et al., "In Vitro Splicing of the Ribosomal RNA Precursor of Tetrahymena" in Cell 27 (1981), p. 487; for a critical analysis, see R. Shapiro, "Prebiotic Ribose Synthesis" in Origins of Life and Evolution of the Biosphere 18 (1988), p. 71.

[3] For a very useful reference on this point that I forgot to include in my published paper, see: T.R. Cech, "RNA chemistry: Ribozyme self-replication?" Nature 339 (June 15, 1989), pp. 507-8.

[4] Besides these references and those in my published paper, see also: D.H. Lee, et al., "A Self-Replicating Peptide," Nature 382 (1996), pp. 525-528; T. Tjivikua, et al., "A Self-Replicating System," Journal of the American Chemical Society 112.3 (1990), pp. 1249-50.

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