January 5, 2010 | David F. Coppedge

Metabolism-First Origin of Life Won’t Work

Evolutionists believe it is necessary to get chemicals up to the point of replication before Darwinian evolution can come into play to build them into giraffes and eagles (given millions of years, of course).  But because it is difficult to imagine a chance formation of nucleic acids (the “genetics first” theory), it has become popular in certain camps to change approaches and imagine metabolism coming into existence first.  These “metabolism first” scenarios envision self-perpetuating cycles of chemical reactions as the first stages in the origin of life.  A team of scientists just showed it won’t work.
    Three European scientists who published a paper in PNAS tried to give the concept a fair shake:1 

A basic property of life is its capacity to experience Darwinian evolution.  The replicator concept is at the core of genetics-first theories of the origin of life, which suggest that self-replicating oligonucleotides or their similar ancestors may have been the first “living” systems and may have led to the evolution of an RNA world.  But problems with the nonenzymatic synthesis of biopolymers and the origin of template replication have spurred the alternative metabolism-first scenario, where self-reproducing and evolving proto-metabolic networks are assumed to have predated self-replicating genes.  Recent theoretical work shows that “compositional genomes” (i.e., the counts of different molecular species in an assembly) are able to propagate compositional information and can provide a setup on which natural selection acts.  Accordingly, if we stick to the notion of replicator as an entity that passes on its structure largely intact in successive replications, those macromolecular aggregates could be dubbed “ensemble replicators” (composomes) and quite different from the more familiar genes and memes.

As they said, perhaps one could generalize the notion of a replicator up to a system or network of molecules instead of requiring a genetic code.  Trouble is, accurate replication is required or the system breaks down:

In sharp contrast with template-dependent replication dynamics, we demonstrate here that replication of compositional information is so inaccurate that fitter compositional genomes cannot be maintained by selection and, therefore, the system lacks evolvability (i.e., it cannot substantially depart from the asymptotic steady-state solution already built-in in the dynamical equations).  We conclude that this fundamental limitation of ensemble replicators cautions against metabolism-first theories of the origin of life, although ancient metabolic systems could have provided a stable habitat within which polymer replicators later evolved.

That last phrase tries to be courteous to the metabolism-first believers by giving them some role as stage hands in the play.  But these authors already stated in the first quote that the genetics-first scenario is plagued with problems of its own – among them, “problems with the nonenzymatic synthesis of biopolymers and the origin of template replication.”  They can’t get the required molecules to form on their own, and then there is the nasty problem of the origin of a genetic code that can copy itself.  The first paragraph in the paper elaborates:

Both schools acknowledge that a critical requirement for primitive evolvable systems (in the Darwinian sense) is to solve the problems of information storage and reliable information transmission.  Disagreement starts, however, in the way information was first stored.  All present life is based on digitally encoded information in polynucleotide strings, but difficulties with the de novo appearance of oligonucleotides and clear-cut routes to an RNA world (but see ref. 6), wherein RNA molecules had the dual role of catalysts and information storage systems, have provided continuous fuel for objections to the genetics-first scenario.

But having demonstrated in their paper the inadequacy of metabolism-first story, viz: “We now feel compelled to abandon compositional inheritance as a jumping board toward real units of evolution,” they could offer no hope on the other hand that the genetics-first scenario was more fit.  All they could supply was faith: “We do not know how the transition to digitally encoded information has happened in the originally inanimate world; that is, we do not know where the RNA world might have come from, but there are strong reasons to believe that it had existed.”  Why?  Because the metabolism-first scenario cannot work: “Template-free systems like composomes could only have had the limited role of accumulating prebiotic material and increasing environmental patchiness.”  There needs to be a storage mechanism for genetic information, and that requires at least RNA.  Storage-based inheritance, not merely attractor-based inheritance, is the minimum requirement for Darwinian evolution: “The essence of nucleic acids from the point of view of inheritance is exactly that they can store a lot of information at roughly equal energy/stability levels, exactly the property one requires from ‘storage.’”
    Later in the paper, they disparaged the habit of applying Darwinian terms, like “selection values”, to prebiotic molecules.  Such terms are “devoid of meaning” in a chemical context, they said.  “The unfortunate usage of words with clear Darwinian connotations—such as adaptation, fitness landscape, and coevolution—in the realm of pre-Darwinian systems cannot be overemphasized.”
Update 01/08/2010: Three days after our report, Science Daily reported about this paper, based on a press release from Free University of Barcelona.  Aside from getting the name of NASA wrong, they defined life as “self-sustaining chemical system capable of Darwinian evolution.”  Even within that questionable definition, the metabolism-first scenario will not work, the article said: “the basic property of life as a system capable of undergoing Darwinian evolution began when genetic information was finally stored and transmitted such as occurs in nucleotide polymers (RNA and DNA).”  Since subsequent Darwinian evolution has nothing necessarily to do with the origin of genetic information, the statement lends more support to a definition of life made by astrobiologist Benton Clark (see 12/30/2002): “life reproduces, and life uses energy.  These functions follow a set of instructions embedded within the organism.

1.  Vasos, Szathmary and Santos, “Lack of evolvability in self-sustaining autocatalytic networks: A constraint on the metabolism-first path to the origin of life,” Proceedings of the National Academy of Sciences USA, January 4, 2010, doi: 10.1073/pnas.0912628107.

We could have told them this.  They are just restating with additional rigor a common-sense principle, that you can’t get inheritance without accurate information storage and retrieval.  The threshold to avoid error catastrophe is too demanding.  Anyway, it’s nice to have their side prove it with eigenvalues and equations.  And it was nice for them to chastise their brethren for misapplying Darwinian terms to chemicals: “The unfortunate usage of words with clear Darwinian connotations—such as adaptation, fitness landscape, and coevolution—in the realm of pre-Darwinian systems cannot be overemphasized.”
    This paper represents the latest in a series of devastating salvos in the battle between the two approaches in origin-of-life studies (see important entry 01/26/2008).  Both sides have both falsified each other and bombed each other’s fortresses to the ground.  Brush aside their false premise that life is defined by its ability to undergo Darwinian evolution; what they really mean is that a lack of accurate genetic replication forbids Darwinian evolution.  But the lack of accurate genetic replication forbids life itself, too, so they lose either way.
    Notice that this team falsified the metabolism-first hypothesis but acknowledged serious shortcomings with the genetics-first hypothesis.  So did they give up and acknowledge that life was intelligently designed?  No: they resorted to what the NCSE would tell you is the antithesis of science: FAITH.  There are good reasons to BELIEVE in the RNA world, they said, simply because their trust in Darwinian evolution requires it, and the alternative, intelligent design, is so horrible to their tender little psyches, they will resort to chance miracles – anything – to avoid going that route.
    Too bad, though.  Stephen Meyer showed in Signature in the Cell that the RNA World scenario, and all naturalistic theories for the origin of specified genetic information, are hopelessly inadequate.  The facts of nature have turned naturalism against itself.  You can’t get here from there.  The origin of life requires the input of information from an intelligent, purposeful source, and science proves it.  That being the case, Darwin becomes superfluous for anything beyond that point, except maybe for explaining minor changes between interfertile finches.

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