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>On Thu, 5 Jan 1995, Tom Holtz wrote: > >> >> Maybe we have to chalk up the missing meter to the Signor-Lipps effect. >> >Given the number of man hours that have gone into trying to find >vertebrate fossils in that meter section, I have hard time just >explaining it away through the Signor-Lipps effect. That tends to come >into play when things have been sampled in a relatively uniform fashion. >This interval, however, certainly doesn't suffer from being under >examined. Therefore, the lack of fossils, be it caused by some primary >or some drastic post-depositional processes, would seem to be real. > >Peter Harries You may not believe that Signor-Lipps had anything to do with it, but mere effort is not enough to overcome that effect. It will always be there no matter how much you look. It has nothing to do with uniformity of sampling either, as the sampling error and biases are present no matter how you do it. Furthermore, negative evidence is no evidence at all, especially in view of an effect like Signor-Lipps. You can feel about it anyway you want (I have my own feelings about what happened), but the Sig-Lipps effect has nothing to do with feelings and everything to do with data. What Sig-Lipps says is that the expected condition will be a gradual decrease (of varying magnitude depending on a variety of original and ensueing conditions) in species diversity towards any set boundary, whether it be artificially placed or natural. What that means is only that you cannot separate a gradual extinction from a catastropic one because all extinctions look gradual because of sampling error and bias of preservation and spatial distribution of the biota. It does not mean that a catastrophe did not take place or that all the bones were dissolved by acid--it means you must seek other evidence not subject to the Sig-Lipps effect. Jere H. Lipps Professor, Department of Integrative Biology Director, Museum of Paleontology University of California at Berkeley Berkeley, CA 94720 510-642-9006 fax 642-1822 jlipps@ucmp1.berkeley.edu
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