Saturday, July 20, 2013
The Uphill, the Downhill, & the Corner Round
I have been walking up high of late, in the Bighorn Mountains of Wyoming. I haven’t had much time for reading or for this blog, but I did pick up Addy Pross’ What is Life again tonight.
Pross argues that there is a law governing “dynamic kinetic systems” (i.e., living organisms) that is analogous to the second law of thermodynamics. Systems governed by the second law tend toward more chemically, physically, and especially thermal stable states. Here is the second law:
The entropy of an isolated system never decreases.
That is to say, an isolated system (one in which no additional energy is supplied) tends toward thermal equilibrium. An ice cube floating in a glass of scotch represents a highly order system (low entropy): the cold and the warm stuff are neatly separated. As the ice melts, the system becomes steadily less ordered until it reaches equilibrium (high entropy).
Systems governed by Pross’ analogous law tend toward more stable replication. Here is Pross’ new law:
Replicating chemical systems will tend to be transformed from (dynamically) kinetically less stable to (dynamically) kinetically more stable.
This law would underwrite the course of evolution. Ants, for example, are very kinetically stable so they remain in their form for a very long period in evolutionary history. Okay.
All material transformations, including all that go on in living organisms, are governed by the second law. Only replicators are governed by the Pross law. Replicators include all organisms but also replicating molecules like RNA.
Here is an analogy that I think captures this point. Consider an alley that slopes slightly downhill. It ends in an intersection with a second alley that slopes from right to left. A boulder rolling down the first alley will always go left when it reaches the junction, because boulders always roll downhill.
A man walking down the first alley is just as much subject to the laws of gravity as the boulder. Nonetheless, the man may turn right at the junction and walk uphill. In order to accomplish this task, the solitary walker must expend stored reserves of energy. If he wants to keep resisting gravity, he will eventually have to replenish his store of energy‑perhaps at the pub atop the hill.
The existence of uphill walkers, while scrupulously observant of the second law of thermodynamics, seems to depend also on Pross’ second law. Organisms exist in forms that are more dynamically stable in the environmental niches that they occupy than the forms from which they evolved.
All that seems reasonable; however, it still seems to me that dynamic stability is a very different kettle of fish from thermodynamic stability. The latter needs only material and efficient causation, as Aristotle described them. The latter, this rock bumped that rock and made it move, is underwritten in modern physics by the second law. Pross’ law of dynamic kinetic stability requires Aristotle’s other two causes: formal (it is this kind of organism) and final (it is up to something).
The big problem for modern biology is how to reconcile the two pairs of Aristotelian causation. Pross’ highly critical discussion of theories about the origin of life illustrates this very well.