Christopher Michael Lowery

Research Associate, University of Texas Institute for Geophysics
  • United States of America

About Christopher Michael Lowery



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Behind the Paper

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Replying to Anne Weil

I'm perhaps less shocked than you that the hypothesis put forth in the Kirchner and Weil (2000) paper was not explicitly tested.  The result of our analysis was that origination rates (peaks and valley) lagged extinction rates by 10 million years.  We were working with Jack Sepkoski's updated database of marine invertebrates. Not too long after that, the database we were using was mathematically adjusted to remove artifacts resulting from the fact that some periods are better represented by the rock record than others. (Might have been Peters and Foote, 2001).  Subsequently, Lu et al. (2006), as we cite in the News and Views, determined that the lag throughout the entire record disappeared if the same methods were used on the adjusted (or "corrected") data set, although long recovery times after mass extinction events remained the rule.

So, I think it was that our core observation did not hold with the data set after the data set was altered. I think only Doug Erwin ever considered that the explanation itself, which was similar to ideas he had, might still apply to mass extinction events.

Also, most people who work on these kinds of questions are invertebrate or micro- palontologists.  Jim and I, as an environmental scientist and a vertebrate paleontologist, did not have a expertise with a group that we could turn around and test it on, the way you and Dr. Fraass have with foraminifera.  

Anne Weil

Well, it could just be my perspective coming into this discussion so much later. I didn't start thinking really critically about mass extinctions until a few years ago, when I sailed on IODP Exp. 364, which drilled the Chicxulub crater. I did my PhD on oceanic anoxic events and had been much more focused on the environmental drivers of plankton ecosystems than on the macroevolutionary ones.  When I learned about  the long delay in the recovery of planktic forams after the K-Pg, which didn't seem to be related to any environmental forcing, I started reading a lot of the extinction and recovery literature, mostly based on Sepkoski's marine invertebrate database. Like most fields I'm not familiar with I'd just assumed the macroevolution people had everything all worked out. When I read your paper I found it extremely clarifying, and then I was immediately disappointed to find the community hadn't spent the next 16 years building off your results, except I think Erwin's paper. It just seemed to me like a very interesting thread had been picked up and then dropped. And, as you said, long recovery times after mass extinctions have remained the rule, so that question was stilling hanging out there even if perhaps it doesn't hold true when the major mass extinctions are removed. Seems like something that might be worth revisiting with a broader database of plankton, beyond just foraminifera, which might have the taxonomic and temporal resolution lacking in the marine invertebrate data.

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