In the ever-entertaining dispute over Darwinian evolution, “irreducible complexity”–IC–has provided a serviceable bone on which intellectual rodents, such as myself, can gnaw. Briefly, for those who have had better sense than to entangle themselves in such brambles, irreducible complexity is the observation–if it is an observation–that many things in biology consist of many parts such that if any one part is missing, the whole shebang fails to function. All the parts would therefore have to evolve–appear–simultaneously. This runs against orthodox Darwinery in which, to get from A to B, everything in between has to evolve bit by bit and has to produce a viable organism every step of the way.
Although much of what Darwin said has little to do with the modern theory of evolution, it is interesting and much to his credit that he foresaw the problem of irreducible complexity:
“If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.”
–Charles Darwin, Origin of Species
Just so. But modern carriers of the evolutionary flame insist that irreducible complexity doesn’t exist.
If it is true that IC does not exist, then in principle it should be possible to simplify organisms backward step by step, running the evolutionary movie reel in reverse, to the level of chemical elements in the ancient oceans, with each stage of simplification producing a living organism. Undertaking this with a large animal, as for example a giraffe, would obviously be impossible. With a simpler entity, it might not be.
We might start instead with a cell. Even this would be difficult to the point, I suspect, of choking in variables. Let us ignore such complexities as cell membranes, vacuoles, endoplasmic reticula, and so on, and deal only with the mechanism of protein synthesis–DNA, RNA, mRNA, tRNA, nuclear bases, transcription, and translation. These are well understood and not impossibly complex. It should not be difficult to simplify the ensemble stepwise back to the level of elements–if protein synthesis is not irreducibly complex.
The advantage of looking for IC in a system using comparatively few components, all of whose structures are understood, is that one avoids being caught in the endlessly arguable confusions of clotting cascades, flagella, metamorphosis in insects, and retinal chemistry. It is probably true that if irreducible complexity exists in protein synthesis, it can’t be hidden and that, if it doesn’t exist, its absence should be unmistakable. The latter result would not rule out IC in other things but, given the fundamentality of protein synthesis, ti would be a large step in that direction.
Note that working backward from an existing mechanism (e.g., protein synthesis) to nonlife is far easier than working forward from nonlife to an existing mechanism. To work forward one must begin with an ocean whose constituents and concentrations one does not know and invent each step. In working backward one already has the mechanism and does not have to invent it, only simplify a tiny bit at a time.
By establishing a path backward to the simple inorganic chemicals of the primeval seas, unevolving backward so to speak, we would also establish a path forward from nonliving to living. Thus we would demonstrate unequivocally a pathway from nonlife to life, though the probability would remain uncertain.
How might we simplify protein synthesis while retaining a viable organism?
We might begin by reducing the number of nucleotides per codon from three to two. This would allow coding for sixteen amino acids, fewer if some combinations were required for other things. Can it be demonstrated in the laboratory, or shown on paper, that this arrangement would give a functioning, reproducing organism? If not, the three-nucleotide codon, and thus presumably the genetic code, would seem to be irreducibly complex.
Now let us consider DNA itself. It is a fairly complex molecule, yet its structure and function are very well known. Surely it must be possible to simplify it to the previous form it had as it evolved toward its present complexity, while still providing a viable organism. This would be impossible only if it were irreducibly complex. What changes might we make as we try to find the compound from which our familiar DNA evolved?
Can the phosphate be removed, and perhaps be replaced by something simpler? Or be done without? The pentose? Purines and pyrimidines replaced by–what? This is beyond me. Doubtless a molecular biologist can light the way–unless it can’t be done at all.
By obvious extension, it should be possible to simplify or eliminate enzymes–RNA polymerase, that sort of thing–to find the viable configuration immediately preceding the current one in evolution. Can protein synthesis be accomplished without enzymes? Surely this can be done, as otherwise one would have to believe that the present system of synthesis sprang whole into being–i.e., is irreducibly complex.
Is tRNA not really necessary? Perhaps it is not, as otherwise it too would seem to be part of an irreducibly complex system. One might even ask how much DNA with with how many codons coding for how many proteins of what lengths would be necessary to keep each earlier evolutionary step viable. But this gets into the generation of information which is another can of worms.
I do not pretend to know the answers. I am just some guy in Mexico with no formal training in biochemistry. Surely those wiser than I can answer these minor questions. Protein synthesis is comprehensible enough that working backwards shouldn’t be difficult. If some biochemist would only take the time to do this, it would do wonders to end the hitherto endless debate about irreducible complexity and intelligent design.
Fred is reachable at firstname.lastname@example.org. Put “pdq” in the subject line of your email will be heartlessly autodeleted. Lack of response usually due to volume, not bad manners.