Subject: Re: Evolution, falsification, and all that. Date: 1 Nov 91 21:43:26 GMT mtx014@cc

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From: Gary Stormo Subject: Re: Evolution, falsification, and all that. From: stormo@boulder.Colorado.EDU (Gary Stormo) Date: 1 Nov 91 21:43:26 GMT Organization: University of Colorado, Boulder Message-ID: Newsgroups: (Robert Low) writes: >I'm not convinced that this is the right place to ask this >question, but I can't think of a better one. So... >Background: Every so often, creationism is described (or >denounced) as non-scientific on the grounds that it is not >falsifiable in any way. "God made it that way" admits of >no counter-examples. So far, so good. >Question: taking the phrase "the theory of evolution" to >be short-hand for "the theory that the mechanism that drives >evolution is variation (from mutation) and natural selection", >would some kind falsificationist tell me what observation >might falsify this theory? (Now, I know that there are >philosophies of science other than falsificationism, but >it is ususally the criterion of falsifiability that is >used to discount creationism, so that's the only group I'm >asking.) >Note: there is a difference between this and having >predictions that are verified. If the prediction >"speciation will be observed" did not work out, we >might simply reply "we haven't been watching long enough". >I'm not asking for predictions that have come out, I'm >asking for predictions whose failure would lead to >rejection/adjustment of the theory. (Or even previous >predictions whose failure would have done so, now that >I think of it.) >For example: would a reliably dated 10^8 year old >hominid fossil falsify the *theory*, or would it >require only that the order in which organisms >evolved be altered, while the mechanism remained? >Disclaimer. Whatever the answer to these questions, >don't think I'm arguing that evolution is no more >scientific than creationism. I may be arguing that >falsifiability is not quite the be-all and end-all >that it is sometimes held up as, though :-) >-- >Robert Low email(JANET): > smail : Mathematics Department, Coventry Polytechnic, > Priory Street, Coventry CV1 5FB, England. >Keep an open mind---but not so open your brain falls out. I would argue that falsifiability is a perfectly good criterion for judging a scientific theory, but one must use a prediction which is experimentally testable. That is if my theory predicts some observation will return a value of X, I must must design the experiment so that some observation is returned, either X or not-X; an outcome of "don't know" (equivalent to your "haven't waited long enough") would mean a poor experimental design or the wrong question was asked. Now to give you an example of an observation that would falsify the theory of evolution. There are many but this type of experiment is most familiar to me and is easily done (in fact it is done all the time by molecular biologists, without yet an occurrence that constitutes a failure of the theory). If has the sequences of a set of genes from different species (the sequences may be DNA, RNA or protein, but the genes must be for the same functions) one can use that information to build a tree of relatedness among the species. Doing this is completely independent of the theory of evolution. I can take any collection of texts and compute the pairwise "distances" between them and then generate a tree (or at least a graph) that corresponds to those distances. The theory of evolution predicts that if I do this for several different sets of genes (ribosomal RNA is a common one to use, as is cytochrome C and several others) that I should always get the same tree (within the accuracies of the distance methods I use). This is a very strong prediction and the fact that there are no exceptions in the thousands of genes that have been sequenced to date has to be among the strongest evidence for evolution. Are the prediction and the experiment to test it clear? Evolution predicts that if you sequence gene X from many different species and build a tree based on those sequences you will get the same tree as has already been determined in many other observations. Gary Stormo | "People will occasionally stumble over the truth, MCD Biology | but most of the time they will pick themselves up Univ. of Colorado | and continue on." - Winston Churchill Boulder, CO 80309 |


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