Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.3 alpha 4/15/85; site cbosgd.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!ihnp4!cbosgd!rlp From: rlp@cbosgd.UUCP (Bob Platt) Newsgroups: net.origins Subject: Re: Now more than ever. PART I Message-ID: <1233@cbosgd.UUCP> Date: Sun, 9-Jun-85 15:10:20 EDT Article-I.D.: cbosgd.1233 Posted: Sun Jun 9 15:10:20 1985 Date-Received: Tue, 11-Jun-85 02:53:19 EDT References: <297@cmu-cs-edu1.ARPA> <1556@dciem.UUCP> <884@mhuxt.UUCP> <1200@cbosgd.UUCP> <477@psivax.UUCP> Reply-To: rlp@cbosgd.UUCP (Joe Knapp) Distribution: net Organization: ATT-BL Columbus OH Lines: 105 Keywords: entropy, evolution >>> from Jeff Sonntag: >>> >>> ...the second law can be >>> applied to evolution only insofar as evolution can be described in terms of >>> heat concentration and temperature distributions *or* if entropy can be >>> defined somehow in terms which are more descriptive of biological systems. >> >> This has been attempted [in] "Structural Stability and Morphogenesis" >> by Rene Thom (Benjamin/Cummings 1975). >> ... > from Stanley Friesen: > > But this still does not address the other aspect of Jeff >Sonntag's objection, that is justifying treating a species as a >thermodynamic system. Even the quotes only specify *how* one would >treat a species as a thermodynamic system, not the reasons why doing >so might be permissible. In short Dr Thom is here making a conceptual >leap without adequate reasons... Well, I pretty much agree that the treatment is far from rigorous. Let me expand the context of the first quote though, as you may have been misled a bit by what appeared to be the opening salvo from a creationist: "If there is only one sufficiently sharp maximum [of entropy], the joint system will evolve toward that state and stay there, neglecting fluctuations. [He continues] On the other hand, if there are several maxima or if the maximum is very flat, we cannot say anything a priori about the evolution of the system, for it could take on one of these maxima, or fluctuate without a well-determined limit." So although the trend is toward a local maximum, an opening is there for an increase in complexity. Rupert Sheldrake in "A New Science of Life" (Houghton 1981), makes the point very well: "In living cells, the physico-chemical systems ... include many potentially indeterminate phase transitions and non-equi- librium thermodynamic processes. In the protoplasm there are crystalline, liquid and lipid phases in dynamic inter-relation; then there are numerous types of macromolecule which can come together in crystalline or quasi-crystalline aggregates; lipid membranes, which as 'liquid crystals' hover on the borderline between liquid and solid states, as do the colloidal sols and gels; electrical potentials across membranes which fluctuate unpredictably; and 'compartments', containing different concentrations of inorganic ions and other substances, separated by membranes across which these substances move probabilistically. With such complexity, the number of energetically possible patterns of change must be enormous, and there is thus a vast scope for the operation of morphogenetic fields through the imposition of patterns on these probabilistic processes." So the problem remains of how to reconcile some intuitive notion of complexity (of the form) with entropy. As you have maintained, it turns out that this is not straightforward. Complexity depends on context. A good example is that of trying to estimate the complexity of the light reaching an organism. A plant extracts merely (but very efficiently) the raw energy of the stream of photons; a mammal extracts information from the patterns of the light waves, facilitating its quest for energy (Thom 1975). We also have to realize that our idea of complexity may not be synonomous (in principle) with entropy, re the following thought experiment: Suppose there is a salt solution at room temperature which is placed into a low-temperature system which is then closed. As the solution cools the salt crystallizes. Intuitively, at least, there seems to have been an increase in morphological complexity in this non-living closed system, although there has clearly been an increase in entropy. In addition, thermodynamics is powerless to explain the spatial distribution of the crystal(s). (Sheldrake 1981) But don't just throw your hands up in mock-despair of ever reconciling these difficulties. You may be afraid that attempts at injecting the principles of thermodynamics into biology are usually a net loss for science due to misuse by ideologues. But don't let that close your mind to every application. And there is some concrete justification for this one. For example, although the form and flow of a river system resists strict thermodynamical treatment, there is no reason to doubt that its morphogenesis is subject to those principles. Thom's insight has been to note the similar morphogenesis of many of earth's forms (e.g. river networks, plant branching, human nervous system development) and to give mathematical justification to many of those observations. The model presupposes a space of external parameters which imposes a certain topology on the way that the form evolves. While the dimension of this space may be very large in principle, often a local model can be constructed that depends on only a few parameters (and observables) and in these cases, the topology of the space can be analyzed, and the "structurally stable" patterns of morphogenesis classified. Entropy (and other measures) plays a role in determining this structure. Since it seems that non-living and living systems do show similar patterns, I believe that the "conceptual leap" if not justified, is definitely worth pursuing. It's refreshing to see the problem of the birth of form tackled head on, not swept it under the rug with the promise that the biochemists will eventually figure it out. Joe Knapp cbosgd!nscs!jmk "I used to be a member of the reptile family, but I'm NOT anymore!" Leonard Zelig