Re: Extinction (was:Religion)

[John Alroy <jack@homebrew.uchicago.edu>]

Whoa! I thought things had calmed down a bit, but Dr. Schwimmer seems  
to have taken offense. Before I start I should note that I have  
passed my Ph.D. defense and finished my thesis but the paperwork  
hasn't gone through yet, so I suppose you can still call me "Mr."  
Alroy.

My comment about "well-articulated arguments" was directed towards  
the VOLCANISM model for a mass extinction, not anti-impact models in  
general. I wasn't aware of the Rampino papers, although it had  
percolated into my consciousness that there really was such  
literature out there to be found. As I had hoped, Stan Friesen had  
the references on hand, and I thank Dr. Schwimmer for the added refs.  
When I said "I'm not aware," I literally meant "I'm spacing on this,  
somebody help me out."

I was jumping the gun when I said that Keller et al. "are trying to  
show that there was no mass extinction"; what I meant was that they  
are trying to show there was no sudden, catastrophic mass extinction.  
Their arguments frequently revolve around whether, say, a 60-70%  
species-level extinction in less than a meter of section is  
"biologically important," which is what prompted me to say this. The  
tone of Keller and Officer's articles is consistently negative and  
that really was the point I was trying to get at.

My quote of the Kerr article was just that, a direct quote. Why slam  
me over it? The occurrence of a seismically-produced tsunami on an  
enormous scale exactly at the K-T boundary seems like an improbable  
coincidence to me, but, of course, this sort of ad hoc, case by case  
assault on the data is exactly what you should expect in phase d of a  
debate like this.

Thanks for the references. I have checked the McLean letter, which  
you said was "a good starting place," and found it to be very  
telling. His main point is that Science published 61 pro-impact  
papers from 1980 to 1993 and four "stricly nonimpact items" in that  
interval, all before November 1989; plus one article that "hinted at  
the possibility of volcanic influence in the K-T extinctions." He  
then goes on to slam Science for violating the First Amendment (I'm  
not kidding), and is rebutted by Daniel Koshland, the editor of the  
journal, who points out that the content of Science largely reflects  
what is submitted to it and what is going on in the field. I can  
think of no better evidence for my original claim that the impact  
issue had long been settled in favor of the idea that an impact  
occurred at the time of a major mass extinction (debate continues  
about cause-and-effect): 90% of the post-Alvarez literature has been  
pro-impact. The fact that old arguments like the "Three Meter Gap"  
(now called a 2 m gap, and actually a 60 cm gap, and I expect it will  
eventually be a 1 cm gap and the anti-catastrophists will still be  
arguing about it) continue to be recycled by people like Williams ten  
or more years after the original debates is additional evidence for  
this claim.

I am unaware of mammal faunas in the Lance straddling the K-T. I  
would be very surprised if there were microvertebrate faunas without  
mammals in this section, so I assume you are talking about dinosaurs  
exclusively. Just for my information, what study has been published  
showing a "gap" at the top of a continuous section through Lance-Fort  
Union (or Polecat Bench, or whatever) contact? My records show  
earliest Paleocene (i.e., Puercan) mammals in Wyoming only in the  
Bighorn Basin, where the terrestrial vertebrate record is minimal (I  
have exactly one, minor mammal locality in the local "Lance  
equivalent"). I do have a recent reference on the Tornillo Formation  
(Schiebout et al. 1987: J Geol 95,359), which specifically notes that  
there is a 35 m barren zone devoid of known terrestrial vertebrates  
that spans the boundary. Therefore, the Tornillo Formation has  
nothing to do with this discussion.
It seems to me that Stan Friesen was correct in the first place in  
noting that the only field area in which anything resembling a true  
"gap" has been found is the Hell Creek area. 


It's hard to believe that after all this discussion I still have to  
field casual ad hominem attacks like "I believe Mike Williams has  
spent a lot of time in the Hell Creek outcrop and has seen the  
evidence first hand.  Have you?" This has nothing to do with the  
issue at hand, which was that Williams' article contained no new data  
or analyses, just qualitative arguments. Your comment about my  
"childlike faith" is similarly insulting and out of place. I have  
previously had to put up with insults directed at my university and  
my major advisor, which is completely inappropriate in a public  
discussion. Have any of my own comments been similarly ad hominem?  
Can we please agree to keep this debate from degenerating into pure  
mud-slinging?

My point about sedimentation rates was that the MAXIMAL duration of  
the 2 meter "gap" was on the scale of 40,000 years, UNLESS there is a  
major hiatus in that interval. I have seen no indication that anyone  
believes there is such a hiatus, in which case my calculations are  
completely reasonable (they also agree with a separate but similar  
calculation made by Friesen). General words of caution about  
interpolating sedimentation rates don't address the fact that this is  
a valid UPPER estimate given the absence of a hiatus. My original  
purpose was to note that a 100,000 - 250,000 year figure for the 2 m  
"gap" was too high.

My five-phase model for the acceptance of new theories pertained to  
the ACCEPTANCE of new theories, not the rejection of new theories. I  
thought this was clear from what I wrote but now I think I should  
have made this more explicit, because Stan Friesen made a similar  
comment. In my opinion a rejected theory never moves beyond my phase  
c, and the impact-based catastrophic mass extinction model has now  
moved to phase d (Friesen doesn't agree and since my argument was  
merely impressionistic I have nothing to say about that). I just came  
across an interesting quote in Raup's Nemesis book to the effect that  
61% of 500 professional geologists and paleontologists in a 1984 poll  
accepted the evidence for an impact at the K-T. This figure would  
surely be much higher in 1994, because there wasn't even a decent  
candidate crater 10 years ago. I also just found a chapter in his  
book entitled "The Three Meter Gap and Other Evidence," which was  
written in 1985! We are not exactly going over new ground here.

Raup didn't come up with the Nemesis model for periodic mass  
extinctions; that's an astrophysicist's responsibility. He came up  
with the statistical data for the extinction pattern and wrote a  
popular book describing the course of the debate. The Nemesis model  
relied on 1) statistical analyses of extinction data, and 2) showing  
that many or most of the "right" extinction events were related to  
asteroid impacts. Because the data are hard to get, the latter is  
still an open question. The statistical analyses were equivocal and  
I'm actually a little surprised there hasn't been more on this now  
that the genus-level data are available (the original analyses were  
based on family-level data).

I think the Kerr quote on the tsunami deposit in Mexico speaks for  
itself. The point is that a VERY HIGH-ENERGY mechanism would be  
needed to explain the deposit, and such a mechanism isn't provided by  
marine regression or Deccan Traps volcanism models.

The comment on Meyerhoff is hardly worth replying to. At this point I  
am starting to get the impression that Dr. Schwimmer believes that  
"expert opinions" are not to be questioned by anyone, regardless of  
how old the data are or whether they are even published! I am not  
comfortable with a vision of science that views decision-making as an  
exclusive right of empiricists with so-and-so many years of field  
experience, and theorists as beneath contempt. This is made clear in  
Schwimmer's insulting comment that I should "try doing some alpha  
field work" myself, as if this would prove to me that simply SAYING  
that a pattern exists is plenty of scientific evidence for it, as  
long as the scientist speaking is a field worker. Personally, I am  
very skeptical of any faunal data that 1) are unpublished, and 2) are  
nearly 30 years out of date, and I say this because I have personally  
compiled 3000 faunal lists and attempted to bring them up to the most  
current taxonomy. What I find over and over again is that faunal  
lists from the 1960's and earlier are almost completely unreliable at  
the species level prior to being corrected.

I agree that the K-T marine regression may have been an important  
contributing factor in the extinction event. However, it fails to  
explain the extremely rapid and severe extinction of terrestrial  
mammals and plants at that time. Regressions of similar magnitude  
occurred several times during the Cenozoic, and there is no evidence  
for a mass extinction of mammals ANYWHERE in the Tertiary record of  
North America! Why would marine regression cause such serious trouble  
for terrestrial communities at the K-T boundary but never again for  
nearly 65 million years? I genuinely find this intriguing.