Wednesday, October 07, 2009

Darwin Bicentenary Part 27: The Mystery of Life’s Origin (Chapter 7)

I have been busy looking at the three online chapters of “The Mystery of Life’s Origin”, a book written by anti-evolutionists Thaxton, Bradley and Olson. The first of these chapters (chapter 7) introduces itself thus:

It is widely held that in the physical sciences the laws of thermodynamics have had a unifying effect similar to that of the theory of evolution in the biological sciences. What is intriguing is that the predictions of one seem to contradict the predictions of the other. The second law of thermodynamics suggests a progression from order to disorder, from complexity to simplicity, in the physical universe. Yet biological evolution involves a hierarchical progression to increasingly complex forms of living systems, seemingly in contradiction to the second law of thermodynamics. Whether this discrepancy between the two theories is only apparent or real is the question to be considered in the next three chapters.

In another passage we read:

It is often noted that the second law indicates that nature tends to go from order to disorder, from complexity to simplicity. If the most random arrangement of energy is a uniform distribution, then the present arrangement of the energy in the universe is nonrandom, since some matter is very rich in chemical energy, some in thermal energy, etc., and other matter is very poor in these kinds of energy. In a similar way, the arrangements of mass in the universe tend to go from order to disorder due to the random motion on an atomic scale produced by thermal energy. The diffusional processes in the solid, liquid, or gaseous states are examples of increasing entropy due to random atomic movements. Thus, increasing entropy in a system corresponds to increasingly random arrangements of mass and/or energy.

Thus far Thaxton, Bradley and Olson hint at a possible conflict between evolution and the second law of thermodynamics. At this stage, however, TB&O don’t claim an outright contradiction but rather an intuitive contradiction that needs to be investigated. Their caution is justified because there is a basic incoherence in TB&O’s statement of the apparent problem. They suggest a parallel between order and complexity, but the fact is that the most highly ordered systems, like say the periodicity one finds in a crystal, are the very antithesis of complexity. They also suggest a parallel between disorder and simplicity whereas, in fact, highly disordered systems, such as random sequences, are in one sense extremely complex rather than simple; their complexity is such that in the overwhelming number of cases they don’t submit to a description via some succinct and relatively simple mathematical scheme. There, is therefore, inconsonance in TB&O linking order to complexity and disorder to simplicity.

What may be confusing TB&O is the fact that highly disordered systems are statistically simple but not configurationally simple: Statistically speaking a very disordered system may be characterized with a few macroscopic parameters whose values derive from means and frequencies, whereas to pin a disordered system down to an exact configuration requires, in most cases, a lot complex of data. Where TB&O seem to fall down in chapter 7 is that they fail to make it clear that living structures are neither very simple nor highly complex, neither highly ordered nor highly disordered but are, in fact, configurations that lie somewhere in between the extremes of order and disorder, simplicity and complexity. As such the characterization of living things is neither amenable to simple mathematical description, nor statistical description.

That TB&O have misrepresented the order/disorder spectrum as a polarity between complexity and simplicity helps ease through their suggestion of an intuitive contradiction between evolution and the second law. Because they have identified high order with high complexity and because the second law implies a move away from order, then in the minds of TB&O it follows that the second law must also entail a move away from structural complexity, thus ruling out the development of the complex living structures as a product of thermodynamics. If TB&O were aware of the intermediate status of living structures in the configurational spectrum they may realize that the situation is more subtle than their mismanagement of the categories suggests.

Another nuance that doesn’t come out in chapter 7 of TB&O’s book is that disorder or entropy, as it is defined in physics, is a parameter that is not a good measure of the blend of complexity and organization we find in organic structures. In physics disorder is defined as the number of possible microscopic configurations consistent with a macroscopic condition: For example compare two macroscopic objects such as a crystal and an organism. A crystal on the atomic level is a highly organized structure and as such it follows that there are relative few ways the particles of a crystal can be rearranged and still give us a crystal. On the other hand a living structure has a far greater scope for structural variety than that of a crystal and it therefore follows that the number of ways of rearranging an organism’s particles without disrupting the abstract structure of the organism is much greater than crystal. Therefore, using the concept of disorder as it is defined in physics we conclude that an organism has a far greater disorder than a crystal. Given the middling disorder of organisms as measured by physics one might then be lead to conclude that in the slow run down of the universe from high order to low order the universe will naturally run through the intermediate disorder of organic forms. Clearly there is something wrong with TB&O’s presentation of the thermodynamic case against evolution. (To be fair I ought to acknowledge that ID theorists Trevors and, in this paper, do demonstrate an appreciation of the intermediate place occupied by the structures of life)

Consider also this quote from TB&O:

The second law of thermodynamics says that the entropy of the universe (or any isolated system therein) is increasing; i.e., the energy of the universe is becoming more uniformly distributed.

Precisely; when compared to the high concentration of energy in a star, the energy distribution in living structures is part of a more uniform distribution of the suns highly concentrated energy and therefore as far as physics is concerned it represents a more degraded form of energy. Admittedly, the thought that physics’ rather crude measure of disorder implies that living structures are an intermediate macrostate in the thermodynamic run down of the high concentration of energy found in a star is counter intuitive, but TB&O have so far failed give a coherent statement of the thermodynamic problem in order to explain this seeming anomaly.

* * *
The second law of thermodynamics works because cosmic systems are walking randomly across the possible states open to them. Given this assumed random walk the overall trend, then, will be for those systems to most likely move toward categories of state with greater statistical weight. It follows, therefore, that classes of states which have a large statistical weight are, as time progresses, the most likely to be occupied by the system; for example heat is likely to move from a hotter region to a colder region because a uniform distribution of heat can be realized with a far greater number of microscopic arrangements than an heterogeneous distribution. A crucial feature of this physical model is the space of possible states. This is determined by the laws of physics which limit the number of possible states available. Through their sharply limiting the number of available states the laws of physics effectively impose an order on the cosmos. Because these laws transcend thermodynamics the order they impose on the cosmos is not subject to thermodynamic run down.

As I have indicated in this post, it is conceivable that the laws of physics are so restrictive, in fact, that they eliminate enough possible states to considerably enhance the relative statistical weight of living structures at certain junctures in the evolution of the cosmos. In effect these laws impose a state “bottle neck”, whereby in the run down to disorder the cosmic system is forced to diffuse through this bottle neck - a place where living macrostates effectively have a realistic probability of existence because their relative statistical weight is enhanced by the laws of physics. However, having said that I would certainly accept that ID theorists should challenge the existence of this state bottle-neck; it is by no means obvious that physics implies such a bottle-neck. But what I do not accept is the anti-evolutionist’s canard that the second law of thermodynamics in and of itself is sufficient to rule out a realistic probability of evolution. If the anti-evolution lobby wants to clinch their case they need to show that physics does not apply sufficient mathematical constraint on the space of possibilities to enhance the relative statistical weight of organic structures at certain stages in the run down to maximum disorder.

I agree with TB&O when they say:

There is another way to view entropy. The entropy of a system is a measure of the probability of a given arrangement of mass and energy within it. A statistical thermodynamic approach can be used to further quantify the system entropy. High entropy corresponds to high probability. As a random arrangement is highly probable, it would also be characterized by a large entropy. On the other hand, a highly ordered arrangement, being less probable, would represent a lower entropy configuration. The second law would tell us then that events which increase the entropy of the system require a change from more order to less order, or from less-random states to more-random states.

But the problem here is what TB&O leave unsaid. There is no quibble with the assertion that the second law of thermodynamics ensures a migration of an isolated system to its most probable class of state, as determined by statistical weightings. But, and this what TB&O don’t acknowledge, the details of that migration are sensitive to the constraints of physics and those constraints apply a transcendent order that is not subject to thermodynamic decay. These constraints may (or may not) considerably enhance, via a state bottle-neck, the probability of the formation of living structures as an intermediate state of disorder in the run down to the most probable state.

That TB&O fail to understand the essential issue is indicated from the following:

Clearly the emergence of order of any kind in an isolated system is not possible. The second law of thermodynamics says that an isolated system always moves in the direction of maximum entropy and, therefore, disorder.

The intent of this statement, presumably, is to dismiss the possibility of the evolution of life on the basis of the second law of thermodynamics. In TB&O’s minds their intuitive conclusion is safe because they have wrongly pushed living structures to the extreme ordered end of the order-disorder spectrum. They see no prospect of life arising because thermodynamic change is always away from order and in TB&O’s flawed opinion it must therefore always be away from the states of life.

Despite TB&O’s initial caution in pushing their belief it is clear that they think their conclusion is safe before they have demonstrated it:

Roger Caillois has recently drawn this conclusion in saying, "Clausius and Darwin cannot both be right."3 This prediction of classical thermodynamics has, however, merely set the stage for refined efforts to understand life's origin.

But to be fair to TB&O they don’t entirely dismiss evolution and they are prepared to consider those refined efforts to understand life’s origin. They engage in some uncontentious thermodynamic analysis showing that the sub systems in a system that is far from equilibrium may decrease in entropy. Hence the only hope that evolution has, they concede, is in the area of systems far from equilibrium. In this TB&O are right. Evolution, if it is to be found at all, will only be found in non-equilibrium systems; that is, systems that diffuse through a conjectured state bottle neck where the squeeze on the available states ensures that the relative statistical weight of living structures is enhanced, thus imbuing them with enhanced probability. But TB&O warn:

Nevertheless, one cannot simply dismiss the problem of the origin of organization and complexity in biological systems by a vague appeal to open-system non-equilibrium thermodynamics. The mechanisms responsible for the emergence and maintenance of coherent (organized) states must be defined.

On that point I certainly agree with TB&O: The appeal to non-equilibrium thermodynamics is vague and general and the mechanisms responsible for the emergence and maintenance of coherent (organized) states must be defined. In other words, is there any real evidence for a state bottle neck, a bottle neck that must be the general mechanism behind evolution? In my next installment I hope to see what TB&O’s chapter 8 has waiting for us on this important question.


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