Re: K/T, Sig-Lipps (or is it Signor-Lip?)

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Well, I'll tell you that if I thought our 1982 paper on this subject was
going to result in a named effect that gets such attention, the authorship
would have been reversed!!  And I don't care what you call  it--Sig-Lipps,
Signor-Lip, Sig-Lip, S&L--just so long as you call it!!  But I would have
preferred now the Lipps-Signor effect, or even better, forget Phil and make
it the Lipps effect.

Anyway I thank Norm for his further explanation of the S-Lipps effect.  I
agree with him.
>
>That having been said though, I'm much more optimistic than Jere about the
>possibility of testing the Signor-Lipps explanation.

RE:  This and Norm's following comments:

Signor-Lipps can indeed be analysized probabilistically.  Signor-Lipps
deals only with the record itself.  Charles Marshall has begun to look at
the probability arguments.  I too am optimistic about science, but we must
be very careful about how we use the data.  That was my only point.
Signor-Lipps was not published to take one side or the other, only to
examine the nature of the record and what it can tell us.  More later from
Lindberg and me--the L/L side effect.

>
>First, recoveries from mass extinction events are
>interesting but they don't address questions dealing with the nature of the
>mass extinction event itself.  To do that you must look to the data
>provided by species that survived the mass extinction event.  Any
>explanation for a mass extinction event that cannot account for the
>composition of the survivor fauna, in effect, explains nothing.

Of course.  I was not addressing the extinction event at all, only what the
biota does from those remaining species.

Second, I
>assume Jere mispoke (mistyped?) the following:
>
>The K/T extinction event evidence comes not
>from paleo so much, but from geochem, mineralogy, and geology.
>>I don't understand how evidence for an extinction event (which I understand
>to be a biotic phenomenon) can come from non-biotic data.  Of course one
>can use the evidence provided by these fields to constrain causal scenarios
>that seek to account for the biotic data.  But the biotic data must remain
>the subject of the explanation and never be relegated to a "supporting"
>role.
>
I didn't mistype, but I was beginning to feel as though I am afflicted with
a case of electronic Giardia, so I cut it too close.
I should have expanded it by typing that I meant most physical causes of
catastrophic extinction, like asteroids, acid, etc.   The species or
functional morphologic selectivity, biogeography, etc. of extinction
clearly can be used to help understand the mechanism of extinction which
might well be quite different than the physical cause of it (I've tried it
myself starting with my first paper in 1970 and some since).   The fossils
are not in a supporting role at all.  They are in a different role--they
can tell us about the conditions that led to their extinction, but surely
the impact of an asteroid for example, by itself, killed few organisms off.
It may well have created conditions that then led to the extinction, such
as blackouts, failed photosynthesis, etc., that the physicists have told us
caused it.  But those guys don't have the slightest idea of the biological
mechanisms involved.  Only we do.  And we should speak up more loudly about
it.  But let's not get involved with them arguing about whether there was
an impact or whatever, or not, because that we cannot address.  That is
truly their realm--and the geochemistry, shocked quartz, etc., is their
evidence.

We could go on, but I think most of us have been over all this many times.
Norm and I are generally in agreement and if anyone has specific questions,
perhaps they could be addressed more fruitfully.

Jere


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