As the diversity of explicit models of trait evolution grow, it will be interesting to see if any consensus develops about which models hold most often in general and whether any insight is gained into which conditions predict appearance of different models.
I think Joe is right that realizing a model is an inaccurate or imprecise description of reality should impel us to develop better models of the world around us, because this partly how science moves forward. However, I don't think pointing out that a model is deficient requires that that person must themselves develop an alternative. After all, an alternative model that capture a more realistic level of complexity may not be possible in some situations (it is certainly possible in trait evolution models, however.) Requiring such a thing would put too much pressure on scientific whistle-blowers, who play a very important role in reminding the rest of us that the world is more than the models we use to understand it and make our predictions. -Dave On Fri, Aug 5, 2011 at 10:51 AM, Joe Felsenstein <j...@gs.washington.edu> wrote: > > Pasquale Raia said: > >> Of course Ted is right, but my problem with this computation, or >> with the >> simple exercise I was proposing is well another: as a >> paleontologist I often >> come across pretty exceptional phenotypes (dwarf hippos and >> elephants, huge >> flightless birds, to make a few examples). When you use methods >> like this (I >> mean Garland and Ives') and compare the output with those >> phenotypes, as I did, >> you immediately realize what the the bottom line is: no matter if >> they are >> nodes or tips, by using the expected (under BM) covariance the >> estimated >> phenotypes are dull, perfectly reasonable but very different from >> anything >> exceptional you may find yourself to work with. This is why I feel >> it is >> difficult to rely on those (unobserved) values to begin with. > > I think that what is being said is that Brownian Motion is too sedate > a process > and does not predict some of the large changes actually seen in the > fossil > record. > > That's a legitimate point but does put the onus on the maker of the > point to > propose some other stochastic process that is tractable and has these > large > changes (and that fits with known Mendelian and Darwinian mechanisms). > Just complaining that the Brownian stochastic process is no good is > insufficient. > > If we want to add the fossils to the calculation, then they will of > course > pressure the Brownian Motion process to change more in their vicinity, > which may help some. > > Joe > ---- > Joe Felsenstein j...@gs.washington.edu > Dept of Genome Sciences and Dept of Biology, Univ. of Washington, > Box 5065, Seattle Wa 98195-5065 > > > [[alternative HTML version deleted]] > > _______________________________________________ > R-sig-phylo mailing list > R-sig-phylo@r-project.org > https://stat.ethz.ch/mailman/listinfo/r-sig-phylo > -- David Bapst Dept of Geophysical Sciences University of Chicago 5734 S. Ellis Chicago, IL 60637 http://home.uchicago.edu/~dwbapst/ _______________________________________________ R-sig-phylo mailing list R-sig-phylo@r-project.org https://stat.ethz.ch/mailman/listinfo/r-sig-phylo
