mrh@cybvax0.UUCP (Mike Huybensz) (12/09/86)
This doesn't belong in talk.politics: followups to talk.origins. While I am well convinced of evolution, there are a few commonly repeated claims which need to be debunked. In article <635@argus.UUCP>, ken@argus.UUCP (Kenneth Ng) writes: > How about that moth that turned black in response to increased air > pollution, and turned gray again in response to air pollution controls? This is THE most often repeated claim of natural selection in action. Industrial melanism of the Pepper Moth is widely repeated in textbooks (which are notorious for the propagation of old, refuted, or pseudo "facts".) However, at a seminar given by Dr. Ted Sargent (one of the foremost experts on predation and color variation within populations of moths), he claimed that the original study was invalid on a host of methodological grounds. The most memorable criticism was that nobody had actually witnessed predation of a wild moth by a bird. While experiments have demonstrated the plausibility of the concealment/predation hypothesis both in the lab and in the forest, it just hasn't been observed in nature. Other problems included sampling biases according to collector and locality. Current research on Biston betularia (the Pepper Moth) seeks to remedy these problems, but it would be difficult to repeat the "experiment" without another industrial revolution. This news makes a good measure of who does and doesn't have a scientific attitude towards evolution. If you can't let go of a cherished belief in the face of evidence, you're not taking a scientific attitude. I'm happy to say that at the Cambridge Entomological Society meeting where this was discussed, alot of people were distraught, but none seemed to reject the position. Unfortunately, I don't think this news has been published yet. Dr. Sargent has made no secret of it, and it is widely known within research circles, but I think he is gathering information to make a definitive statement. > How would you explain the increased resistance to DDT from insects? This is a good example of artificial selection (no more natural than industrial melanism of the pepper moth.) There is a vast scientific literature on increasing resistance to pesticides. Crop pests develop resistance to most pesticides within 3 to 10 years, creating a sort of biochemical arms race between the chemical companies and the pests. In article <189@cpro.UUCP> asgard@cpro.UUCP (J.R. Stoner) writes: > And how about the evolution of Haike crabs in Japan. It has been seen that > these remarkable creatures evolved (with carapaces with likenesses of samurai > on them) within recorded history. Legends say these crabs are the souls of > warriors who drowned in the bay after a failed sea battle. Fishermen would > routinely throw back into the water any crab that had any semblence to a > warrior. In the course of time a whole new species appeared with _very_ > good images of recognizable japanese faces on their carapaces. This sounds like a pretty little just-so story to me. It should be possible to gather good evidence of this, perhaps from shell middens, or by comparing populations that have been selected with populations that haven't. I doubt that such evidence exists. How can we observe current evolutionary change? The very first thing we need is baseline data. You can't say change has occurred unless you can make a comparison. For the near future we will have difficulty, because there are few "before" samples (other than fossils) that we can use for comparisons. In the intermediate distant future, we will be able to compare populations that were introduced to islands with baseline data being collected right now. -- "Enough of acting the infant who has been told so often how he was found under a cabbage that in the end he remembers the exact spot in the garden and the kind of life he led there before joining the family circle." Samuel Beckett -- Mike Huybensz ...decvax!genrad!mit-eddie!cybvax0!mrh
mrh@cybvax0.UUCP (Mike Huybensz) (12/09/86)
Followups to sci.bio and talk.origins (definitely not the kids newsgroups!) In article <2778@gitpyr.gatech.EDU> dts@gitpyr.UUCP (Danny Sharpe) writes: > I've heard that, due to lawnmowers, dandelions in suburban areas are being > selected for shorter stems. This is probably not true. The last I read about it (about 12 years ago), our common weed dandelion is thought to be entirely one clone. Its seeds are produced apomicticly: a somatic cell becomes the embryo. The great variation of form we see in dandelions is not genetic, but developmental. It is possible for sports (mutations within clonal lines) to occur, but I don't know of any research identifying sports in dandelions. > And then there's all the diseases that have become > resistant to the drugs used to treat them. Yes, this is a good example of selection. > These are all examples of natural selection at work. Neither of these is natural selection, in that the selection pressures are being applied by man. -- "I have yet to see any problem, however complicated, which, when you looked at it the right way, did not become still more complicated." Poul Anderson -- Mike Huybensz ...decvax!genrad!mit-eddie!cybvax0!mrh
mrh@cybvax0.UUCP (Mike Huybensz) (12/09/86)
Followups to sci.bio and talk.origins. In article <2849@bu-cs.BU.EDU> bzs@bu-cs.BU.EDU (Barry Shein) writes: > For what it's worth I believe the acid test of a new species is that > it is no longer able to breed with the original species it evolved > from. Morphological changes alone aren't sufficient (until which time > those changes prevent inter-breeding.) What you believe is irrelevant. :-) The fact is that biologists cannot decide what constitutes a species. Many will tell you that species are really fictions. But useful fictions. Different criteria are used to decide what species are in different taxa (groups of organisms). This isn't due to the fact that different workers have different opinions. It's due to the fact that no single definition is useful for all taxa. The complications arising from the diversity of organisms and the sources of that diversity make your test impractical. First, there is the temporal question: is a species today really the same species that existed X years ago? How can we test if the ancestral species has died out? What if hybridization is possible but the progeny are less fit (or even sterile)? Say hybridization can occur in the lab but doesn't in nature? Because of distance? Because of different pollinators? Because of different behavior? What about continuously interbreeding populations whose members at opposite extremes of the range can't interbreed? What about parthenogenetic organisms? Is every one of them a species? -- "People always HAVE eaten people; people always WILL eat people. You can't change human nature!" (From "The Reluctant Cannibal" on the Flanders and Swann album "At The Drop Of A Hat".) -- Mike Huybensz ...decvax!genrad!mit-eddie!cybvax0!mrh