Bruce, Suddenly can't think what the evidence would be for "most mutations are lethal." Given the tremendous capacity of the developmental system to absorb variation and produce a common result, how would we know. The best we could know is that most visible mutations are lethal.
This is a brain fart, isn't it. Oh Dear. Nick -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Bruce Sherwood Sent: Thursday, May 12, 2011 8:44 PM To: [email protected] Subject: [FRIAM] What evolves? I'll take a stab at Russ's question, "What's the analogous force (or other explanation) for void filling in evolution?" Dawkins presents what seemed to me a helpful way of seeing why mutations are usually lethal. He invents a multidimensional space in which a point represents a possible living creature, whose attributes are coordinates on each of the very large number of axes (e.g. length, mass, number of legs, etc.) He points out that this space is enormously empty, as most points represent creatures that are not viable. Moreover, any mutation that represents a big jump in this multidimensional space takes you to a point in that space representing a nonviable creature. Viable creatures are represented by clouds of neighboring points, surrounded by vast empty spaces. New species (to the extent that "species" is a meaningful term) to be viable will be near these clouds. If a cloud is densely occupied, a new species will most likely be found just outside the cloud, exploiting an until-now "void" but with only small changes from the attributes of existing creatures in this grouping. In this metaphor it seems to me that void-filling is "driven" essentially "entropically" -- to exploit a larger space. The analogy would be a gas confined in a small portion of a large empty box. Remove the barriers, and it looks to the observer as though the gas is "driven" to fill the void. But at a micro level all you see is molecules running around randomly, sometimes colliding with other molecules or the walls. According to mechanical laws, the gas could continue to occupy a small portion of the otherwise empty box, or return to such a configuration after making excursions. But there are so many more ways of arranging the molecules to exploit the entire space of the box that there is a crushingly large probability any time you look in the future of finding the box completely filled. In the process of this filling, it "looks" to the observer as though the gas is "driven" by some "force" to occupy the large space. But that's an illusion. Or you can I suppose define an equivalent "entropic force" doing the driving. Incidentally, when I only recently read The Origin of Species I was struck by how much ecology there is in the book. At one point Darwin specifically says that one of the largest influences driving the evolution of species is the other species in the environment. And the last few pages are a wonderfully lyrical paean to an ecological view of interacting organisms (his English river bank). Bruce Sherwood Russ Abbott russ.abbott at gmail.com Thu May 12 00:13:53 EDT 2011 Previous message: [FRIAM] What evolves? Next message: [FRIAM] What evolves? Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] Lots to respond to. First of all, Nick, why do you say I am discarding the distinction between living and non-living. I don't recall saying that. To Dave's point: By "fitness" I mean nothing more than 'void filling' ... There is no "process" anymore than there is a "process" when water in a flooding river 'fills voids' on the other side of the levee. That still leaves open the question of the scientific explanation for how voids are filled. Is there a physical force that produces that result? In the case of water going downhill, the force is gravity. What's the analogous force (or other explanation) for void filling in evolution? What's the scientific explanation for how it happens? *-- Russ Abbott* *_____________________________________________* *** Professor, Computer Science* * California State University, Los Angeles* * Google voice: 747-*999-5105 * blog: *http://russabbott.blogspot.com/ vita: http://sites.google.com/site/russabbott/ ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org ============================================================ FRIAM Applied Complexity Group listserv Meets Fridays 9a-11:30 at cafe at St. John's College lectures, archives, unsubscribe, maps at http://www.friam.org
