Thursday, December 24, 2009

Darwin Bicententary Part 30: The Mystery of Life’s Origin, Chapter 9

Continuing my consideration of the three online chapters of Thaxton, Bradley and Olsen’s book “The Mystery of Life’s Origin

Absence of Evidence…

In chapter 9 of the Mystery of Life’s origin Thaxton, Bradley & Olsen start by expressing the essential mystery of life’s origin:

In Chapter 7 we saw that the work necessary to polymerize DNA and protein molecules from simple biomonomers could potentially be accomplished by energy flow through the system. Still, we know that such energy flow is a necessary but not sufficient condition for polymerization of the macromolecules of life. Arranging a pile of bricks into the configuration of a house requires work. One would hardly expect to accomplish this work with dynamite, however. Not only must energy flow through the system, it must be coupled in some specific way to the work to be done.

What TB&O are saying here is that although the energy required to carry out the work of organizing atomic and molecular units into a living configuration may be available, that energy in itself is useless without some kind of information engine directing how it is to be used. An analogous situation arises if one has a large work force of men; this work force is all but useless unless they have the information on how to act.

In chapter 9 TB&O look at the crucial question of abiogenesis; that is, the question of whether disorganized elemental matter has the wherewithal to organize itself into complex living structures. They consider a variety of proposed mechanisms: Pure chance, natural selection, self ordering tendencies in matter, mineral catalysis, non-linearity in systems far from equilibrium and the direct production of proteins and DNA. Needless to say they are of the opinion that at the time of writing no substantive model of abiogenesis exists. I am not aware that the situation has improved substantially in favour of abiogenesis since TB&O’s book was written in the mid eighties.

TB&O’s main point comes out very clearly when they consider experimental attempts to directly form polypeptides. TB&O believe that most theories of abiogenesis founder in one important respect: Whilst they accept that under the right disequilibrium conditions organic polymers can be synthesised, they point out that these polymers are randomly configured, and thus by implication contain no useful information content. In TB&O’s opinion the chief challenge to theories of abiogenesis is the question of what supplies the necessary “configurational entropy work”. In their words:

Virtually no mechanism with any promise for coupling the random flow of energy through the system to do this very specific work has come to light. .

TB&O tender experimental results which suggest that the formation of polypeptides shows no bias in the frequency of connections:

The polymerization of protein is hypothesized to be a nonrandom process, the coding of the protein resulting from differences in the chemical bonding forces. For example, if amino acids A and B react chemically with one another more readily than with amino acids C, D, and E, we should expect to see a greater frequency of AB peptide bonds in protein than AC, AD, AE, or BC, BD, BE bonds.

Furthermore, the peptide bond frequencies for the twenty-five proteins approach a distribution predicted by random statistics rather than the dipeptide bond frequency measured by Steinman and Cole. This observation means that bonding preferences between various amino acids play no significant role in coding protein. Finally, if chemical bonding forces were influential in amino acid sequencing, one would expect to get a single sequence (as in ice crystals) or no more than a few sequences, instead of the large variety we observe in living systems. Yockey, with a different analysis, comes to essentially the same conclusion.

Coupling the energy flow through the system to do the chemical and thermal entropy work is much easier than doing the configurational entropy work. The uniform failure in literally thousands of experimental attempts to synthesize protein or DNA under even questionable prebiotic conditions is a monument to the difficulty in achieving a high degree of information content, or specified complexity from the undirected flow of energy through a system.

This kind of evidence supports TB&O’s belief that there is no natural information mechanism that can correctly configure an arrangement of atoms:

We have noted the need for some sort of coupling mechanism. Without it, there is no way to convert the negative entropy associated with energy flow into negative entropy associated with configurational entropy and the corresponding information. Is it reasonable to believe such a "hidden" coupling mechanism will be found in the future that can play this crucial role of a template, metabolic motor, etc., directing the flow of energy in such a way as to create new information?

*****

My own reaction to TB&O’s rather negative assessment of abiogeneis is that if they are genuinely interested in the possibility of a natural route from inorganic matter to functioning organisms they are looking in the wrong place and therefore find what they expect: No evidence of abiogenesis. But if they do start looking in the right place there is a major epistemological snag: it likely to be in the nature of abiogenesis (and evolution as well) to be difficult to observe.

If natural abiogenesis has occurred on our planet then, as I have already mooted in this Darwin Bicentenary series, the coupling mechanism providing the information for abiogenesis is likely to be found in the arrangement of structures in morphospace; for abiogenesis to work there must exist a connected class of stable structures with complexities ranging from the very simple to the very complex; that is abiogenesis requires biological structures to be reducibly complex. This structured class is an object that is neither dynamic nor visible but instead is a static platonic structure that, if it exists, must be implicit in the laws of physics. The information for abiogenesis and evolution is not going to be found in chemistry that encodes the right information in biopolymers in a straight forward way. The information structures, if they exist, will be found in a mathematical object spanning morphospace, an object that has no material reification.

The scientific challenge faced by those committed to abiogenesis (and evolution too) should not be underestimated because abiogenesis may be a computationally irreducible processes. If this is true then it follows that there is no simpler analytical proof of the existence of abiogenesis other than to observe the actual processes that generate life. In this case the evidence of abiogenesis will rest less on theoretical analysis than it will on observation. Hence an absence of fossil evidence becomes a serious barrier to scientific progress in abiogenesis and will add plenty of fuel to the fire of anti-evolutionism. Another problem for theories of abiogenesis is that if there is a natural route from inorganic matter to living structures then fossil evidence is likely to largely comprise of unstructured chemical signatures of equivocal interpretation. Researchers are thus left with little choice but to propose very tentative and speculative chemical scenarios that might look as though they have the potential to generate life. But if TB&O have presented the evidence fairly then it is clear that no consensus theory of abiogenesis exists, let alone a theory with a robust observational base.

TB&O in common with other anti-evolutionists conflate information and complexity:

Regularity or order cannot serve to store the large amount of information required by living systems. A highly irregular, but specified, structure is required rather than an ordered structure.

Whilst I would give a qualified acceptance to the idea that information is conserved in that it requires prerequisite resources either in the form of highly improbable pre-conditions or the huge spaces of a multiverse, is it not true in general that structural complexity cannot be “created” from regularity in relatively short times. Fractals and pseudo random sequences are an example of a “free lunch” complexity derived from simple starting conditions in polynomial computation times. As yet I know of no principled reason why the complex arrangements in morphospace required by abiogenesis cannot also be generated relatively rapidly from the right physical regime of laws. ID theorists may tell us that “equations and equations don’t generate Complex Specified Information” but in spite of that assertion equations can A) be the depository of large amounts of information, B) create complexity in polynomial time, and C) therefore be used to specify complex static forms. (See my last post)

The anti-evolutionists appear to rule out abiogenesis on the basis of the methodological rule “absence of evidence is evidence of absence”. But ardent evolutionists may claim that the onus is on ID theorists to demonstrate that biological structures are irreducibly complex and therefore cannot be product of abiogenesis and evolution. See this post of mine for the ironies of this stand-off between evolutionists and anti-evolutionists. The irony is further compounded when one hears atheists attacking theism on the basis that there is no God because “absence of evidence is evidence of absence”. God and evolution are both very complex objects so perhaps it is not surprising that like abiogenesis it is in the nature of God to be difficult to observe!

No comments: