February 20, 2002 | David F. Coppedge

Darwin Propagandist Reveals Too Much

You can’t always tell a chocolate by its coating.  Similarly, a positivistic, pro-evolution article might have surprises inside.
    “Billions of years of evolution have produced organisms of stunning diversity,” begins E�rs Szathm�ry in the Feb. 17 issue of Current Biology,1 with vintage Darwinian confidence.  A theoretician at heart, Szathm�ry explores the evolutionary transitions not by looking at bones or genes, but by “making models of intermediate stages of organisation and the evolutionary transitions between them.”  Theoretical biology had its Golden Age, he claims, when Fisher, Haldane and Wright founded population genetics in the first half of the twentieth century.  As he justifies his conceptual-over-empirical approach, he reveals some large gaps in evolutionary theory.  He evidently feels Darwinism provides enough conceptual material in each case to fill in the gaps, but it will be up to the reader to judge his success:

  • Non-intuitive explanations:  How can apparently unDarwinian aspects of biology be explained?

Take evolutionary biology, for example.  A few decades after the Golden Age, evolutionary biologists started to tackle (ultimately with considerable success) questions where the Darwinian answer is far from obvious.  Why do we age?  Why are there sterile insect castes?  At first it does not seem to make much sense to argue that your death or sterility increases your fitness.  But evolutionary theory can provide satisfactory resolutions of these conundrums.  In some cases even the question itself cannot be formulated well enough without some modelling: the problem of the evolutionary maintenance of sex is a case in point.  Whole sub-disciplines, like evolutionary game theory, have been set up to meet such challenges.
(For more on evolutionary game theory, see 02/10/2004 entry.)

  • Cosmic evolution:  What can we predict about what evolution would do on another planet?

The problems become a lot harder when we come to the large-scale dynamics of evolution.  Imagine, say, a thousand Earth-like planets with exactly the same initial conditions of planetary development.  After one, two, three billion years (and so on), how many of them would still have living creatures?  And would they be like the eukaryotes?  We have simply no knowledge about the time evolution of this distribution, and ‘educated’ guesses differ widely.

  • Origin of Life:  “Undoubtedly, the origin of life remains a major challenge for at least two disciplines: chemistry and biology,” he says.  (One might wonder what other scientific disciplines would have greater import on this question.)  He reviews the famous experiment of Miller and Urey, but dismisses its actual relevance:

Still, when contemplating life’s origins, the gap between Miller’s world and the DNA world is discouragingly enormous.  How do you get from the primordial soup to the genetic code?  The snag is that, in contemporary biological systems, there is a division of labour between nucleic acids and proteins: the former store genetic information and the latter exert function.  Genetic information is expressed with the help of proteins, which are encoded by nucleic acids.  We seemed to be at an impasse: no genes without proteins and no proteins without genes – the classic ‘chicken and egg’ problem.

Szathm�ry is not the first, of course, to point out this conundrum, but he quickly suggests that “it now seems that the primordial soup may not have been that important, and that we may not need a genetic code for early life.”  As support, he refers to the “RNA World” hypothesis, that one molecule (RNA) might have performed both information-storage and enzymatic functions.  How this would obviate the need for a soup of chemicals or a genetic code is not explained.

  • Models vs. reality:  How far can you take a model?  He praises the “chemoton” model by Hungarian theorist Tibor G�nti, but cautions about the applicability of any model:

The chemoton is an abstract model of a minimal biological system comprising three sub-systems: a metabolic cycle producing the materials for all three sub-systems at the expense of nutrients; a replicating template; and a boundary membrane.  All three systems are autocatalytic, and the system as a whole can also divide in space within a certain parameter range.
Important advances often come from appropriate abstraction and idealisation, neglecting unnecessary detail.  This neglect cannot, unfortunately, be automated: science remains the art of the soluble.

Nevertheless, he thinks G�nti’s modeling is as valid as were Galileo’s experiments with smooth balls rolling down smooth slopes.  Comprehending this analogy is left as an exercise.  (For more on requirements for minimal life, see the 02/15/2004 entry.)

  • Has evolutionary biology succeeded in explaining the first life?  No, but we may be on the verge of beginning to find a way, he thinks.  In promoting conceptual approaches over experimental, however, he pretty much shuts down production of the primordial soup line:

The simplest autonomous living systems today are prokaryotes, the results of billions of years of evolution.  There is just no way that a prokaryote with its genetic code could have self-assembled in the primordial soup.  There must have been a long phase of evolution by natural selection from the first living entities to bacteria, as G�nti recognized in 1971.  But how can one think of these earliest systems?  Chemoton theory offers such a conceptual breakthrough.

From here he jumps to trends in synthetic biology, seeming to promise “the check’s in the mail” on the origin of life.

1E�rs Szathm�ry, “Magazine: From biological analysis to synthetic biology,” Current Biology, Vol 14, R145-R146, 17 February 2004.

When your opponent is shooting himself in the foot, there is really no need to return fire, but rather to sit back and enjoy the entertainment.

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Categories: Dumb Ideas, Origin of Life

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