|
<By this do
you mean "if all analyses do not agree perfectly, none of them
can be right"? The weatherman can't track the weather prefectly in all cases, but he can get close enough to roughly make plans for the week.> As I read them, you're making two different points in this paragraph. Both are built on an implicit answer to the question 'will a cladistic analysis produce a correct answer without the intervention of the analyst?' If the answer is yes, then you would have to assume that evolutionary principles, the Universal Law, are perfectly reflected in the algorithm. In that case, then proving a single analysis wrong or proving that two adequate (however defined) cladistic analyses produce contradictory results would refute the yes answer. Because your second observation assumes that the analyses can produce inaccurate results, I think your answer would be no, that the analyst is necessary. This means that the judge of the adequacy of included characters becomes the analyst, subject to peer review. I like the observation in another post that essentially the use of cladistics is to demonstrate a process of thought. The problem with that is the algorithm becomes a limitation, in that the logic available to the analyst is what is available to her/him through the computer program. You appear to confirm this when you say: < The "universally applicible rules" that a cladistic analysis is based on are: 1. If two taxa share a character, it is more likely to represent homology then convergence. 2. The more traits that taxa have in common, the more likely they are to be closely related, and a taxa will be more closely related to a taxon with more characters in common Now, as a lot of the previous discussion has focused on, neither of these points is always true. Convergence is very common. Moreover, some characters, usually complex ones, are probably less likely to have developed independantly then a suite of relatively simple ones that might be likely to be tied together, which is why I like the idea of running seperate analysis that take out character suites that may be particularly susceptible to homoplasy to see what happens.> You can see what happens when the basis of analysis may be incorrect: you develop workarounds. Why not abandon the cladistic structure if you have to defeat it by denying it the full set of characters in order to determine a correct solution? If cladistics is only a form of presentation, aren't you arguing that it is an inconvenient form? <Even if some characters should be weighted more then others, if you get a bunch of (probably) unconnected light-weight characters that all seem to point in the same direction there is an implication there.> Is the implication that you have discovered something about the evolutionary relationships among a group of animals, or that your means of analysis may have provided you with a misleading result? You may well be able to resolve this problem, using your own insight and intelligence and experience. You probably will. But that will not be because of the quality of the particular tool you have been using, no? |