Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site dciem.UUCP Path: utzoo!dciem!mmt From: mmt@dciem.UUCP (Martin Taylor) Newsgroups: net.bio Subject: Re: limited evolutionary variation Message-ID: <761@dciem.UUCP> Date: Tue, 6-Mar-84 17:25:36 EST Article-I.D.: dciem.761 Posted: Tue Mar 6 17:25:36 1984 Date-Received: Tue, 6-Mar-84 20:21:48 EST References: <509@uofm-cv.UUCP> Organization: D.C.I.E.M., Toronto, Canada Lines: 34 ================= A more interesting question is how those limits are enforced. Ideally, there would be a biological mechanism that limits change. Demonstrating such a mechanism would be, I think, another excellent way to falsify the evolutionary theory. ================= (Limits, in the above == limits on variability of species form). I don't see the connection. Surely there exists a perfectly natural set of limitations on the variability of any species. Some limits apply because the organism would die (and many do, before and after birth), some apply because the organism in its modified form would find no ecological niche and would be unlikely to reproduce as effectively as the "mainstream" version of the species. Isn't the filling of ecological niches what lies behind punctate equilibrium? We know from the results of breeding domestic animals that drastic changes can be developed in a few tens of years when selection is deliberate. The genetic mechanisms ALLOW very fast changes in species form. But in nature, the empty niches created by the Lords of Breeding (us) seldom are there for the changed forms to occupy. If some disaster occurs and niches open up, then rapidly varying forms can occupy them. If there is a general extinction from whatever cause (sea-level transgression, asteroidal impact, nuclear war), then the whole niche structure ceases to be self-supporting and the whole list of major and minor species can be rapidly transformed. In sum, evolutionary theory seems to demand a biological mechanism for limiting species variability, rather than being open to falsification if one were discovered. -- Martin Taylor {allegra,linus,ihnp4,uw-beaver,floyd,ubc-vision}!utzoo!dciem!mmt