On Mon, Oct 13, 2008 at 12:18:11PM -0600, Nicholas Thompson wrote: > > Russell Wrote ===> > > Any extinction event is a collapse of the food web. And selection only > proceeds by means of extinction. So I'm not really quite sure what > you're trying to nuance here. > > Nick Replies ===> > > OK. Here is where we disagree, I think. Let's worry this a bit, before we > talk about anything else, because it seems absolutely central: When talking > about selection, at what level of organization are we speaking? Gene, > individual, small group, "deme", species, ecosystem? etc. I grew up under > the influence of George Williams who argued that no entity above the > individual could serve as a level of selection and of Richard Dawkins, who > argued that no entity above the level of the gene could serve as a level of > selection. So, in my world, species level selection is not a powerful cause > of evolution. Indeed, on some definitions, species, by definition, cannot > compete. Now, in the last decade, I have thrown off Williams' shackles and > started to talk about selection at the level of the small group. And, > indeed, I do know that some others have started talking about species-level > selection. But species level selection has not become the received view, > has it???? If no! > t, the statement above must be EXTREMELY [whoops, _extremely_] > controversial. > > Let's pause here and see what others say. >
I don't think there is disagreement, more a difference in perspective. You are focussing on short term evolutionary change, aka microevolution. I'm more interested in long term evolutionary change, or macro evolution, which is composed of speciation and extinctions. Of course evolution must proceed via changing genetic frequencies, as otherwise how will a single mutation come to dominate an entire gene pool. However, once established, a given haplotype will rarely become extinct in a sexually reproducing population unless that population is very small, and that will only happen in a genetic bottleneck or true species extinction. Nothing of what I said earlier has anything to do with the group selection debate (although I do tend to think, along with EO Wilson, that group selection effects exist). It just comes from think of the mechanics of evolution at an ecosystem scale, where species are the individual components of the ecosystem. In this view, a dramatic change in behaviour of a species (say radical alteration of prey species, or successful defence against some previous predator) that is not in response to a change elsewhere in the food web, would really constitute a new species, even if technically the new and old versions could still interbreed. -- ---------------------------------------------------------------------------- A/Prof Russell Standish Phone 0425 253119 (mobile) Mathematics UNSW SYDNEY 2052 [EMAIL PROTECTED] Australia http://www.hpcoders.com.au ---------------------------------------------------------------------------- ============================================================ 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
