How are entropy and evolution related?

Many discussions about evolution are based on inaccurate considerations of entropy and complexity. One common fallacy asserts that entropy is a universal tendency toward disorder, that evolution is a process leading to greater order, and therefore that evolution is somehow negentropic.

Complexity is sometimes defined as the number of bits needed to precisely describe a system. This definition implies that orderly systems can be described more compactly than systems that seem more disorderly. That would seem to contradict the usual notions that entropy is some kind of tendency toward disorder, while evolution is a tendency toward complexity.

Entropy refers to dispersal of energy. Evolution refers to diversification of form. Both involve a time-dependent relationship between what is actual and what is possible.

A more useful definition of entropy is that it is a measure of the tendency of energy to become less concentrated over time by occupying a greater number microstates. The more concentrated a source of energy, the greater the likelihood that it will move into configurations in which it is more diffuse. Energy tends to dissipate or spread out as time passes, and so transformations leading to more dispersed energy are more probable than transformations leading to more concentrated energy.

Entropy brings about unceasing change. Arrangements of matter and energy continuously appear and disappear as energy flows and disperses. Any particular arrangement is usually only one of a vast number of possible arrangements, and is unlikely either to persist or arise again unless it leads to greater dispersal of energy. Therefore, those arrangements that do happen to be stable will accumulate over time as other arrangements disappear.

Persistence is an important factor in any evolutionary process. Evolutionary processes depend on some sort of selective barrier to reversibility. Replication is a possible mechanism for achieving this, but other frameworks for establishing memory are theoretically possible. In general, evolutionary processes also nearly always involve selecting higher activation thresholds, either thresholds for chemical reactions or thresholds for analogous transformations in whatever space the evolutionary process is unfolding.

Although persistence is a necessary factor in evolutionary processes, is it the essential characteristic? Is evolution really the tautological principle that survivors persist, or is it more subtle than that?

In a poetic sense, evolution is the condensation of time itself. By definition of space, even of abstract space, separate events cannot occur in precisely the same place at the same time. Therefore, a definite increment of time is ineradicably necessary for a finite number of possible configurations to be traversed and explored. The incompressibility of space is at the core of evolutionary processes in general.

Taken abstractly, a system evolves when it moves through a pattern space and accumulates records of that space. The more space it has traversed, the more evolved the system. As a system becomes more highly evolved, it accumulates records that reduce the number of fruitless trials and enable it to connect directly to regions of space that are more richly connected to other patterns within that space. The evolving system builds upon and exploits its experience to discover wormholes through the pattern space.

In this sense, evolution is analogous to entropy, although evolution is morphological rather than energetic.

Michael Webb, 2000

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