Sunday, May 24, 2009

Darwin Bicentenary Part 20: Does Evolution Violate the 2nd Law?

All anti-evolutionists that I have heard commenting on the Second Law of Thermodynamics claim that evolution violates this law. This assertion is a slogan that does the rounds in the anti-evolution community and is second only to the cry that information cannot be created. It is likely that both slogans are popular because they give the appearance that rigorous science is being employed to refute evolution. The ID community who host many anti-evolutionists cannot now backtrack on this slogan without considerable loss of face and consequently they put up a stiff fight in its defense. But is the second law really the killer argument against evolution?

My sixth attempt to get this graph right (Click to enlarge)

The above graph represents the increase in disorder of an isolated system of cosmically significant dimension. The disorder is shown as capital Z (Note: I don’t have an “omega” character available just at the moment). The value of Z at time t represents the huge number of possible microscopic combinations that are consistent with a system that has been developing for time t. (Entropy S, by the way, is given by S = k Log Z).

On the same graph I have superimposed another graph for the quantity I call w. This quantity represents the number of microscopic combinations taken from the huge set of combinations enumerated by Z which have the property of containing life. I have shown this graph as a hump because it is likely that at the extremes of order and disorder life is impossible. Hence I conclude that there is a limited time window during which life can exist, a window which I have marked as “Life’s window”.

Now, the evolutionist’s conjecture is that without resort to anything more than the “law and disorder” normalcy of the physical universe, there is a realistic chance of organic structures evolving in the life time of the universe. A necessary condition of this conjecture is that the ratio w/Z is significant enough to ensure that a cosmos containing a sufficient number of these quasi isolated systems will return a realistic chance that life will evolve somewhere. The ID theorists, on the other hand, are effectively telling us that this is nonsense and that w is far too small in relation to Z to return a realistic chance of evolution in spite of the size of the universe. In other words, ID theorists are telling us that the hump I have drawn is of negligible height.

Looking at the graph of Z one thing is clear; the system represented by the graph must be under a very tight physical constraint. This fact is evident from the smooth increase in Z; the system clearly cannot make sudden random leaps to anywhere in the space of possibilities. It follows that the behavior of the system in time is highly constrained, preventing such disordered jumps. In fact the behavior of Z is consistent with a system that makes incremental steps according to some variant of random walk. This ordered dynamic in no way contradicts the second law. It hardly needs be said that the meta-constraints of physical law, which are responsible for this continuity of change, are not subject to the second law, as the latter describes behavior within these constraints.

In the light of the foregoing it is clear that if evolution is to work its success must be encoded in the meta-constraints of physical law; this follows because only the constraints of physical law can sufficiently limit the value of Z in order to raise the ratio w/Z to a magnitude which returns a realistic probability of life evolving. Under these conditions evolution, far from being a violation of the second law, would in fact be an outcome of the second law. This is because the second law is the engine that forces the exploration of system possibilities, thus ensuring evolutionary outcomes receive their share of the probability on offer which, provided w/Z is sufficiently large, will have a significant value. In short, provided w/Z is great enough, the second law does not prevent evolution; in fact it does the very opposite: it facilitates evolution. Evolution is only a violation of the second law if w/Z is too small for the evolution of life to be realistically probable. But without specifying this variable it is wrong to claim that evolution is an in principle violation of the second law.

The general conclusion that under the right conditions the second law must be the engine of evolution rather than a block to evolution, does not mean to say that in practice evolution is possible given the particular set of laws and constants that govern our own cosmos. Those laws and constants may not set a sufficiently high value of w/Z to favour evolution. Moreover, ID theorists Abel and Trevors, in this paper, contest the idea that physical law of any kind can be the logical source of evolution. Abel and Trevors tender two challenges to the notion of some kind of physical law being the putative logical source of evolution:

a) Simple algorithmic laws generate monotonous simplicity like, for example, crystal lattices, and cannot source the complex structures of living things.

b) If simple algorithmic laws determined the structures of life then those laws would prohibit the degrees of freedom needed by life’s information bearing media like DNA, thus rendering those media useless. According to Abel and Trevors, life’s information bearing structures are “dynamically inert” in that their configuration is not determined by physics and chemistry and necessarily so according to them.

Abel and Trevors’ very interesting and probing paper really needs its own post to do it justice, something I hope to do at a future date. However, here are my first reactions to the above two points:

a) Simple to complex mappings are possible. Short algorithms can generate complex configurations, including, to a good approximation, random sequences; although admittedly with respect to the huge number of possible complex objects, the number of algorithmically reducible objects is very small.

b) If basic physics and chemistry implicitly encode the highly complex forms of life, then this encoding must be embodied in a morphospace containing reducibly complex organisms. Thus physics and chemistry is not required to directly generate the appropriately encoded information bearing structures of life, thus limiting their degrees of freedom. Morphospace is a static platonic object with no degrees of freedom and is given once and once only. As such it does not require the degrees of freedom needed for reuse in order to store new information. Therefore it does not need to be, as Abel and Trevors put it, “dynamically inert”.

If evolution has happened then its deeper cause traces back to the complex platonic object of an algorithmically reducible morphospace implicit in the laws of physics and Chemistry. It is this object that guides evolution via its available pathways of reducible complexity. This object, then, must be reducible on two counts: 1. It must be algorithmically reducible and 2. It must be reducibly complex in the sense that it must contain pathways along which the random walk of evolution can diffuse. Such an object is not entirely unprecedented: Human progress has been fed by a “Technological Morphospace” that is also implicit in the laws of physics and chemistry and contains artifacts that are reducibly complex with respect to the given human quantum of intelligence (see part 18 of this series).

1 comment:

James Knight said...

Nice one Tim. Keep up the good work.