Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!tdatirv!sarima From: sarima@tdatirv.UUCP (Stanley Friesen) Newsgroups: sci.bio Subject: Re: Paranormal phenomena and evolution Message-ID: <106@tdatirv.UUCP> Date: 29 Jan 91 00:06:50 GMT References: <1435@gtx.com> <6735@harrier.ukc.ac.uk> <104@tdatirv.UUCP> <6747@harrier.ukc.ac.uk> Reply-To: sarima@tdatirv.UUCP (Stanley Friesen) Organization: Teradata Corp., Irvine Lines: 113 In article <6747@harrier.ukc.ac.uk> sss3@ukc.ac.uk (S.S.Sturrock) writes: >In article <104@tdatirv.UUCP> sarima@tdatirv.UUCP (Stanley Friesen) writes: >>This form was essentially an semi-terrestrial, bipedal >>ape, not very different from a modern chimpanzee. > >Umm, the modern Chimanzee is just as evolved as we are, see later, >Australopithicus probably shared a common ancestor with Pan I suppose. >Semi-terrestrial? Like a lungfish perhaps :-) Did I ever say otherwise. I was only saying that A. afarensis probably *looked* very much like the chimp (particularly the pigmy chimpanzee). I was *not* trying to claim common ancestry. I was claiming, and still calim, that A. afarensis had not evolved very far from that common ancestor, and that in most respect the chimpanzee has remained conservative. (The main change in the chimp appears to be the development of knuckle-walking, and probably a shift in coat color.) And yes the latest evidence strongly indicates that A. afarensis was only partially terrestrial. It had a pelvis and hind leg adapted for walking upright, but it also had the long curved fingers, long toes and shoulder structure of a brachiating ape. [In fact it shares more features with brachiating apes than with modern humans, so by raw character count it would seem to have been almost purely arboreal.] Or did you think I meant semi-aquatic? I was contrasting 'terrestrial' with 'arboreal'. [Maybe I have been reading too many papers by primatologists, who routinely make this contrast in this way - (e.g. a Baboon is terrestrial, a Guenon is arboreal)]. >>No it is not. Evolution (in the biological sense) implies *genetic* change. > >Did I mention genetic change? Nope, doesn't mean it is not evolution. >As I see it, evolution is a response to an environmental change, so, are >you saying that a better diet is not environmental? This may be your definition, but it is *not* the one used by trained biologists. We restrict the term evolution to alteration due to genetic differences. Thus, as long as you use your own private definition of evolution when talking to biologists you will get this sort of misunderstanding. > The capacity to be >tall may have been around for a long time but it was not expressed, it is >now. Depends on what you consider to be evolution, for instance two >groups of organisms might be identical genetically (at least within their >gene pool) but have behavior differences which mean they will never cross >breed, is that evolution? If we start getting bogged down in just the >genetic change scenario we may be simplifying the situation too far. No it is not evolution, it is an environmental barrier to breeding, that may, with time, lead to the gradual evolution of intrinsic breeding barriers. Only if the behavioral differences have a genetic basis would a biologist claim that evolution had occurred. Note that externally imposed differences in behavior or form may ultimately become incorporated into genetic changes. So such a situation is often the source of the selective pressure that causes evolution (in the biological sense). >Maybe my view of evolution is not strictly the Biological one, but since >I trained as a Palaeontologist and had to deal with very dead organisms >I didn't get much chance to study the genetics of evolution. This is >of course an old argument between Biologists and Geologists/Palaeontologists. >In terms of fossils, any change in a species *has* to be put down to evolution >because we don't have any other answer close at hand. Change in size >of organism within a population is most definately important. Hmm, I think this is changing. Certainly paleontologists are paying more attention to population biology issues. Also, I believe that purely environmentally driven changes are not sufficiently stable to show up in the fossil record. The difference in time between 1200 and 2000 AD would be totally unresolvable in the geological column. Thus a paleontological sample of modern Homo sapiens would end up lumping all late Holocene people into one bucket. No temporal trend would be visible at all. [Indeed, if our civilization disintegrates the nutritional levels will revert to the old values, and small sizes will again prevail, all within a geologically instantaneous time.] [I.e. if you can see a directional change in the fossil record, it almost has to be genetic to have lasted long enough to see]. In fact it is this instability of non-genetic change that has lead biologists to restrict the term evolution to genetic change. >... It can be seen in the fossil >record that species may experience long periods in which no external >change in appearance has occured. But this does not mean evolution has >stopped, the capacity for >a change can continue to happen without being expressed, then when the >environmental pressure changes the organism can adjust quickly, as is also >seen in the fossil record. Who is right? I have never seen any convincing evidence for this style of genetic change. [And a change in 'capacity' must necessarily be genetic]. That is, except for random genetic drift, genetic differences must be expressed to be preserved by evolution. And there is no reson to expect that random changes will lead to any particular change in an organisms fundamental cpacities for expressing various traits. > I don't know, biologists have a >great deal of soft tissue to play with, but palaeontologists have a broard >timescale. Maybe we should go back to cladistics! :-) Gads, I hope not! I am getting sick enough of the cladistic assumptions in the research papers on dinosaurs! By the way, my main area of biological interest is paleontological. My two specialites (right now) are dinosaurs and advanced primates. [But I am having trouble keeping up on primates, since the primate paleontologists are not publishing as many symposia as the dinosaur ones, and I am too busy writing computer programs to do a proper literature search] -- --------------- uunet!tdatirv!sarima (Stanley Friesen)