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On Thu, 5 Jan 1995, Jere H. Lipps wrote: > > 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. > Somewhere along the way, what I wrote has been unfortunately misconstrued to imply that I had said anything about the nature of the extinction event itself. The only point that I was trying to make, I gather rather ineptly, was that the absence of bones throughout the western interior of the US needs to be explained. If the Signor-Lipps effect is going to cover all the environmental, diagenetic, and sampling problems then so be it, but I feel that we would be better served to try to explain such phenomena in as much detail as possible. Who knows, it may tell us something about the ever-elusive causation. Peter Harries
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