sss3@ukc.ac.uk (S.S.Sturrock) (01/29/91)
In article <15242@milton.u.washington.edu> jespah@milton.u.washington.edu (Kathleen Hunt) writes: > >Sorry, evolution *must* include genetic change. This is the biological >definition. You can discuss environmentally-caused variation if you like, >but please don't call it "evolution" or we will all get confused. The Biological definition may be incorrect. > >I think you are mixing up timescales here. On the paleontological timescale, >changes which appear to be "instantaneous" may actually have occurred quite >smoothly. By "smoothly" I mean that large evolutionary changes do not >spring full-blown from nothing, but must build up over a series of >generations -- i.e., no "hopeful monsters", or at least very few hopeful >monsters. [There are some exceptions (allopolyploidy in plants, for >example).] You may think I am belaboring the obvious, but creationists have >this silly habit of thinking that `evolutionists' believe that complex >organs like the eye sprang into being in a single generation...it is for >the creationists' sake that I'm pointing this out. <Stuff Deleted> >And by the way, cladistics is alive and kicking! There's a good seminar >on cladistics at my school right now...I haven't taken it but it looks >pretty interesting. "Abolish Reptilia!" > >I get the feeling you are saying that the mere passage of time counts as >evolution -- that is, that if a population existed for millions of years >with exactly the same frequencies of alleles (this is highly unlikely, >and I'm ignoring mutation), you would say it had evolved. I don't >think this is right. If I have misunderstood you, please set me straight. I find it highly amusing that Cladistics could be considered as being alive and kicking. Maybe I am wrong but it relies on shared features to define a similarity between species ie wings, therefore birds are closely related to insects, and bats?!!? :-) What about polyphyletic origins, take the 'phylum' Arthropoda. Hmm? Maybe you can give me a little fresh data. For timescales take a look at the PHYLUM Trilobitomorpha. Species in this phylum evolved rapidly, very rapidly in fact, and the strata that the fossils are preserved in can often be resolved down to seasons! Tell me that isn't a fine enough resolution. :-) Anyway, there are regular instances when an organism has evolved suddenly, again, how about the Ammonoidea? I am quite clear about timescales involved, what about the horse, there are NO inbetween fossils, just individual, identifiable species. This is the crux of the matter, it is simple to argue that they have stopped evolving, but to then say that 'overnight' they changed to a new species and left no record? No I am not a creationist, or a Christian or any other religion. I would like you insights, or any others for that matter. Shane Sturrock, Biol Lab. Canterbury. Great Britain.
sarima@tdatirv.UUCP (Stanley Friesen) (01/30/91)
In article <6761@harrier.ukc.ac.uk> sss3@ukc.ac.uk (S.S.Sturrock) writes: >In article <15242@milton.u.washington.edu> jespah@milton.u.washington.edu (Kathleen Hunt) writes: >> >>Sorry, evolution *must* include genetic change. This is the biological >>definition. >The Biological definition may be incorrect. Except in this case 'correct or incorrect' is not a meaningful question. The meaning of the term is in some sense arbitrary, and determined purely by accepted usage. In biology the term evolution is *defined* to mean "genetic change, expecially in response to environmental factors". It has been given this definition by deliberate choice, because it is the most useful in biological contexts. This is how technical terms work, they are given a precise definition that meets the needs of the scientific community. >I find it highly amusing that Cladistics could be considered as being alive >and kicking. Maybe I am wrong but it relies on shared features to define >a similarity between species ie wings, therefore birds are closely related >to insects, and bats?!!? :-) Sigh, I am no fan of Cladism, but this is just a straw man, the definition of shared derived characters is *much* more precise than this. Such an silly argument has never been seriously proposed by any cladist. >What about polyphyletic origins, take the 'phylum' Arthropoda. Hmm? The interesting thing here is that even the cladists disagree over this one! [In fact cladists often tend to disagree alot, since the cladogram generated depends sensitively on the set of characters used and how they are analyzed]. Indeed it is this instability that I take to be one of cladisms biggest weaknesses. Especially since it cladists claim to be *removing* subjectivity and instability. >For timescales take a look at the PHYLUM Trilobitomorpha. Species in this >phylum evolved rapidly, very rapidly in fact, and the strata that the fossils >are preserved in can often be resolved down to seasons! Tell me that isn't >a fine enough resolution. :-) That depends, is the thickness of trilobite fossils greater than the thickness of the bedding planes? I suspect that they are, in which case this is *not* the level of resolution. The, and more important difficulty, is that this resolution is only good *within* one outcrop, it cannot be even extended to other outcrops of the same formation. Thus there is no way of determining if the sudden changes are immigrations, climatic shifts or what. The *effective* reolution is thus quite a bit worse as far as population and biogeographical analysis are concerned. (And these are the types of analysis that are necessary to demonstrate evolution). >Anyway, there are regular instances when an organism has evolved suddenly, >again, how about the Ammonoidea? I am quite clear about timescales involved, >what about the horse, there are NO inbetween fossils, just individual, >identifiable species. This is the crux of the matter, it is simple to argue >that they have stopped evolving, but to then say that 'overnight' they changed >to a new species and left no record? No I am not a creationist, or a Christian >or any other religion. I disagree here, at least as far as the Equids are concerned. There is quite a bit of intermediacy. It is just that any one sample can be characterized as a population, so that the level of intermedicay is determined by sampling limits. Try checking out Clemens work on Yarrow in California, and then trace the reference chain forward through the literature. The appearence of discrete populataions in the original study was entirely due to small number of samples. The sample set for Equids is about comparable in density to Clemens original study. This is true for most other 'well-studied' fossil groups. I also know of one, fairly early, study of trilobites in which over msot of the range the new species replaced the old suddenly, but there was a small geographical area in New York with an intermediate, polymorphic population. The study was one of the two that formed the basis for the punctuated equilibrium theory. It is interesting that it clearly shows a brief, localized, period of essentially gradual change in the origin of a new species. -- --------------- uunet!tdatirv!sarima (Stanley Friesen)