Monday, December 26, 2005

I've been rather careless about my reading/recently read lists. My reading is just not that well organized. I may put a book, or several, on hold while I read something else that caught my interest, maybe because it relates to questions that I've wondered about for a long time. The Plausibility of Life by Marc Kirschner and John Gerhart is one of those books that impose themselves to my attention. Rather than summarizing how Kirschner and Gerhart present the problem and their solution, I find it easier to present the problem and solution in computer science terms. Suppose we have a complex computer program that is subject to random corruption. Our intuition is that random bit changes will either have no effect or make the program crash miserably. It would be extremely unlikely that the program would be improved by a random bit change. However, consider instead a program made of several core components that are robust to corruption (through redundancy and self-checking) and can adapt to changing demands from their computational environment (through feedback and learning). Furthermore, assume that the components can be rearranged for many different functions with appropriate computational glue, which itself is subject to corruption. Then it becomes much more plausible that random bit changes will not crash the program, but instead lead to novel functioning. When I had thought of computational analogs of living systems and evolution, which is natural for a computer scientist interested in biology, I had implicitly assumed something like the second alternative, but without articulating it explicitly. That's what Kirschner and Gerhart do, for the mechanisms of life themselves, without computational metaphor but with extensive empirical backing. If you want to read just one biology book the next year, this should be it. The language is sometimes turgid and repetitive, and some points could I think be made more clearly and strongly by presenting explicit information flow/control models, but on the whole this is the book that clears up for me the puzzle of the creativity of mutation. 5:25:23 PM