Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site cybvax0.UUCP Path: utzoo!linus!philabs!cmcl2!seismo!harvard!talcott!panda!genrad!mit-eddie!cybvax0!mrh From: mrh@cybvax0.UUCP (Mike Huybensz) Newsgroups: net.origins Subject: Re: Dog Breath, In the Year of the Plague Message-ID: <526@cybvax0.UUCP> Date: Thu, 9-May-85 12:54:17 EDT Article-I.D.: cybvax0.526 Posted: Thu May 9 12:54:17 1985 Date-Received: Sat, 11-May-85 23:58:03 EDT References: <1012@uwmacc.UUCP> Reply-To: mrh@cybvax0.UUCP (Mike Huybensz) Distribution: net Organization: Cybermation, Inc., Cambridge, MA Lines: 141 In article <1012@uwmacc.UUCP> dubois@uwmacc.UUCP (Paul DuBois) writes: > > In response to some of Ron Kukuk's postings, two or three people have > given the dog as an example of observable evolutionary change. > Certainly they appear to vary widely. In reply, I offer the following. (Many lines of examples deleted to keep me from appearing on the list of biggest posters. :-) > I conclude from such considerations as the above that the dog is not a > very good example of significant evolution and simply represents > intraspecific variation. The facts seem to me rather in line with what > some creationists refer to as "variation within a kind." Of course it does. Because creationists have never said what constitutes a "kind". No matter how large a pattern of variation (or evolution) you present, a creationist can just dismiss it as "a kind". > There are, however, at least two phenomena that give me pause, so that I > would not try to apply this as a universal rule. > > (i) Drosophila do reach the point of reproductive isolation. Thus > they qualify as different biological species. > (ii) Polyploidy in plants generates instant (biological) species. > Mike Huybensz has been hitting us creationists on the head with > this one (perhaps he would phrase it a little differently) and > rightly so. Polyploidy results in an instant reproductive > barrier. The polyploid plant cannot reproduce with its parent > stock, though it can reproduce with other plants like itself > quite happily. When one considers that about half of the > 300,000 known species of angiosperms (flowering plants) are > polyploids, the significance of the phenomenon becomes clear. Thanks for the complement. It warms my heart to see acknowledgement that my points are telling from such a confirmed skeptic of evolution. > It seems to me that this is certainly something for creationists > to consider. The "kind" would have to be defined very broadly > to account for this (I think - am I wrong?). Not at all: the idea of a kind in no way rules out reproductive isolation within a kind. The problem is though, that if one allows reproductive isolation within kinds, you then are not parsimonius in your original assumption of multiple kinds. In other words, the single "kind" that represents all life is more parsimonius than the multiple kinds that creationists claim originated as in Genesis. > I suppose that I should add that I see this as a problem in > regard to the definition of "kind" only, not in the sense that > it must somehow be explained away in order to rule out > evolution. That is not necessary. It is a widespread > phenomenon; however, we may reasonably ask: what does > polyploidy produce? First, observe that its occurrence is much > more common in plants than in animals, where the incidence is > very much lower. One might expect then that if plant evolution > had actually happened in this manner that we would see more > species of plants than animals. In fact the number of species > of animals is much greater than that of plants. So it would > appear not to have played that large a role. Actually, there has been substantial speculation that polyploidy was quite important in the evolution of the higher taxa of the vertebrates. I don't know where it has gone lately: it struck me as rather fanciful. But the question of reproductive isolation from mechanisms other than polyploidy would still be very important to creationists. > Second, polyploidy does not result in addition of anything new, > it only increases the quantity of what is already present in > existing organisms. So it does not solve the problem of the > evolution of new structures. Polyploidy can allow new features. First, by recombination of alleles in ways that were not possible before. Second, by providing working space for variation in extra copies of genes. For example, say there is a vital gene. If it mutates to something that cannot perform the vital function, but is useful in another way, it would be strongly selected against in a normal diploid organism. In a polyploid organism, there would be little or no selection against it: the organism can have a set of two ordinary vital genes and one or more of the mutant gene in the other set of chromosomes. The polyploid organism could have its cake and eat it too. > Finally, I would like to point out for further reference that if > evolutionists wish to use dogs as an example of evolutionary change, > then another claim that has been made (the claim of "only 100 years or > observed artificial selection") goes out the window. It would be more > like, I suppose, 10,000 years or so - 100 times longer! (14,000 > according to Patterson). And what do we have after 10,000 years?? Lots > of different dogs, morphologically different, but interfertile. Thus > they are not even biological species (reproductive isolates). 100 years for fruit flies is approximately 2500 generations. For dogs, 10,000 years is approximately 10,000 generations. The difference is not that great. You also provided examples of non-interfertile varieties of dogs (Great Danes and Saint Bernards.) But that's not germaine to the question of species. Species is a descriptive term: it has no real existence any more than "large" does. Like "large", it varies depending on the context, and like "large" it is a term whose use is a matter of convenience in description. When we talk about species, we want clear boundaries: but they may not exist. Reproductive isolation in nature seems to be common (though not always 100% isolation.) We like to delineate species where reproductive bottlenecks occur and where the character differences are most reliable. Domesticated animals tend not to have reproductive bottlenecks because humans haven't selected for them. There is substantial evidence that natural selection for reproductive bottlenecks does occur. That's why it is usually inappropriate to talk about domesticated varieties being different species, but why it is appropriate to talk about wild species that can be crossed in the laboratory. > See, e.g., Hitching [p39]. > > "Nor have these experiments simply happened during the last century or > so. Ever since Neolithic man started crossbreeding wild varieties of > grass, such as einkorn, more than 10,000 years ago, plant domesticaion > can be seen in the archaeological record. Domesticated dogs arrived > about the same time. Yet in the whole of this time period, there is no > hint of wheat or dogs changing into anything except different kinds of > wheat and dogs." Hitching overlooks quite a number of things here. First, he overlooks maize, which is amazingly different than its ancestor teosinte. Check the recent (past 4 years) article in Scientific American on the origin of corn. Second, wheat is primarily polyploid. Most varieties are tetraploid or hexaploid. Putative wild species are diploid. But mostly, we have a lack of specificity of what kinds are: we might just as well describe humans as a different kind of fish. The creationist idea of a kind includes limits to variation. It is up to them to show the limits: evolution postulates none. -- Mike Huybensz ...decvax!genrad!mit-eddie!cybvax0!mrh