I've been trying to follow this discussion with little profit until I read this last posting from Wirt Atmar. This is the most intelligent, succinct, evocative and accesible (and inspiring) explanation I've ever read on the topic of basic evolution. Maybe it's old-hat to evolutionary biologists, but it's going to be part of this wildlife ecologist's permanent lexicon.
Thanks, Wirt, for persisting on this topic. Warren Aney Senior Wildlife Ecologist Tigard, OR -----Original Message----- From: Ecological Society of America: grants, jobs, news [mailto:[EMAIL PROTECTED] Behalf Of Wirt Atmar Sent: Tuesday, 18 July, 2006 14:20 To: ECOLOG-L@LISTSERV.UMD.EDU Subject: Re: Maldaptation, Extinction and Natural selection Dan writes: > I am not an expert on evolution (far from it) but I have a > hunch that relates to Hutchinson's quote and analogy about > "the evolutionary play in the ecological theater". Let me say that you can do no wrong by reading and memorizing G. Evelyn Hutchinson, and especially his student, Robert MacArthur. The metaphor I tend to use however invokes a different art form, that of a movie. The study of ecology, which entails investigations into the totality of the biotic interactions we find on earth, is like the last, current frame of a movie that has been running at 24 frames per second for the last several hundred years. When we do ecology, we're looking only at the last frame of the movie. Ecology is evolution in "now" time, captured in the current frame, but no matter how intricately we tease apart the ecological physics of those interactions in this last frame, the interactions will never make complete sense unless they are examined over the course of the entire movie. The "ghosts of competitions past," where pronghorn antelope run at high speed from a cheetah that's no longer present on the North American plains, is as good an example as we have of the necessity of imposing time into our studies, making Hutchinson's "the evolutionary play in the ecological theater" phrase all the more relevant. Why are developing these metaphors important? On one hand, saying all of this is obvious. On the other, these discussions have almost no practical value when you're in the field, taking detailed measurements. But "science" doesn't mean "data." The mathematician Henri Poincare wrote, "Science is built of facts the way a house is built of bricks, but an accumulation of facts is no more science than a pile of bricks is a house." "Science" literally means "understanding," and without developing these perspectives, we really don't understand much of anything. Evolving truly accurate mental metaphors and models is fundamental to doing science, of any stripe. Saying this, what then of the idea of the "evolutionary algorithm"? In that regard, you write: > My hunch combined with your analogy below of "evolution as > algorithm" might be considered "ecology as operating system". > This focuses on ecology at the ecosystem and biosphere level. > Your description of the algorithm seems to explain and > characterize selection well, but it does not seem to account > for 1) generation of novelty, other than via random or > error-related mutation, 2) feedbacks that result when the > organisms and communities/ecosystems alter the environment > and then have to adapt to their own alterations (as studied > in "niche construction" and "ecosystem engineers") and > 3) the infrastructure and maintenance of elements, energy, > materials that make the instantiation or materialization of > new forms ("actors") possible, participates in juxtaposing > them in new "plays" and "cleans up the mess" after the "play" > (i.e. decomposition and recycling) so that the "theater" is > not cluttered from past performances. I could convert these > to algorithm or application/program vs operating system > examples relation to hardware realizations, memory and/or > disk space/clutter. > > Algorithms are great, but for them to work one needs an > operating system that can continue to "run" and allow many > "programs" to "run" and that is robust and does not itself > "crash". There is also work by folks following up on Robert > Rosen that suggests that much of the essence of life process > is non-computable, not algorithmic and non-mechanistic. Some > of the work here focuses on ambiguity and circularity, both > of which algorithms do not handle well but life seems > accustomed to. I previously wrote the evolutionary algorithm as: "Given self-reproduction, Darwinian evolution is composed of only these five components: o a bounded arena o a replicating population which must eventually expand beyond the bounds of the arena o thermodynamically inescapable replicative error, guaranteeing variation within the reproducing population o competition for space in that arena among the inevitable variants o the consequential competitive exclusion of the lesser fit" But it's important to note that Darwin probably would have said the same thing, if the word "algorithm" had been in use 150 years ago. What he did write, in the final paragraph of his last chapter in "The Origin of Species," was this: "It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing on the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner, have all been produced by laws acting around us. These laws, taken in the largest sense, being Growth with Reproduction; inheritance which is almost implied by reproduction; Variability from the indirect and direct action of the external conditions of life, and from use and disuse; a Ratio of Increase so high as to lead to a Struggle for Life, and as a consequence to Natural Selection, entailing Divergence of Character and the Extinction of less-improved forms. Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows. There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one; and that, whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved." This is one of the most quoted paragraphs in all of biology, but the feeling I get when I see it repeated is that most people are using it merely as a poetic description of his ideas. I don't believe Darwin meant it to be taken that way. If you're going to read Darwin, you must first understand that beyond his being a superior observationist, he was a hard-nosed mechanist, as much as any physicist or engineer. He wanted to understand process and mechanism, and in doing so, gave evolutionary theory for the very first time a very clearly defined physics. I've written before here that we're not doing ourselves any favors by saying that "ecology has no laws." More than that, I believe the sentiment to be nonsense. When I look at nature, I see nothing but rules, where Darwin's physics merges seamlessly into the ecological physics of competitive exclusions, carrying capacities, faunal relaxations and the like. If Darwin lived today, in a modern world of bullet-pointed PowerPoint slides, his last paragraph would probably look like this: o Growth and Reproduction, and by consequence, Inheritance o Variability in form o Ratio of Increase leading to a Struggle for Existence o Natural Selection as a consequence o Leading to Divergence of Character o And the Extinction of less-improved forms This is the Darwinian algorithm, as explicitly outlined by Darwin himself. If this is truly an algorithm, who or what then is doing the processing? Nature, of course. Given self-reproducing entities, the Darwinian algorithm is the inescapable consequence of reproduction in a positively entropic, bounded universe. Finally, as long as we're on this paragraph, let me speak to one other, unrelated item, one that deals with Darwin's phrase, "There is a grandeur in this view of life," a sentence which is also often quoted. My own idiosyncratic reading of these last few sentences is that he was speaking primarily to himself, trying to salve his conscience for the physics he was proposing, a physics built on death, disease, famine, pestilence and predation. To do that, he wrote an extremely uncomfortable truth: "Thus, from the war of nature, from famine and death, the most exalted object which we are capable of conceiving, namely, the production of the higher animals, directly follows." I personally feel the same way. In any universe that I would build, there would be no death, no aging, no sickness or war. The only rub is that I have no idea how such a world could either come into being or how it could be maintained. In Darwin's alternate universe of death and famine, we unfortunately have a simple, easy-to-understand mechanism, one that does eventually builds the most exalted objects which we are capable of conceiving, the production of the higher animals. Wirt Atmar
