I develop statistical methods to study evolution and extinction in the fossil record.

Mass extinctions and the Signor-Lipps effect. When a collection of taxa (e.g., species of dinosaurs or ammonites) are killed off simultaneously in a mass extinction, their last occurrences in the fossil record may nonetheless give the impression of a gradual extinction, due to the incompleteness of the fossil record (the Signor-Lipps effect). I develop methods for testing whether a mass (sudden) extincton has occurred, and for estimating the position and duration of such an extinction. I also study the related topic of placing confidence intervals on stratigraphic ranges, i.e., estimating the time of extinction of a taxon based on its fossil record.

Evolutionary trends. Large-scale trends in the history of life (such as increase in body size, a.k.a. "Cope's Rule") may be a result of driven mechanisms (e.g., selection) or passive mechanisms (e.g., diffusion away from a lower bound). Several tests have been developed to categorize a trend as either driven or passive, but real trends are likely to be a combination of both types. I have developed a new method, the Analysis of Skewness, to quantify the extent to which a trend is a combination of driven and passive trends. With Jon Payne of Stanford and members of his lab, I also study trends in animal body sizes over time; see our recent paper in Science.

Macroevolution. Using statistical analysis and paleontological databases, I study large-scale questions about the history of life. Sample questions include: (1) Are mass extinctions merely larger manifestations of processes responsible for background extinction, or are they a fundamentally different phenomenon? (2) How many kinds of dinosaurs ever lived, and were dinosaurs already declining before an impact at the end of the Cretaceous Period caused their ultimate extinction? (3) Are observed extinction rates in mass extinctions a reliable guide to the severity of the triggering mechanism? That is, does a higher extinction rate indicate a more severe cause, or can factors such as Simpson's paradox make such an inference misleading?

The tempo of the Cambrian explosion. The Cambrian explosion was a key event in the history of life, in which representatives of most phyla (animal body plans) first appear in the fossil record. With Susannah Porter and John Moore and of UC Santa Barbara and Adam Maloof of Princeton, I am working on developing a statistically rigorous timeline of Early Cambrian originations, accounting for a number of possible biases such as dating error and incomplete fossil sampling. This problem is analogous to the Signor-Lipps effect in mass extinctions, but in the reverse direction.

Dynamics of extinction in food webs. The end-Permian mass extinction was the most severe in the history of life, but its causes remain enigmatic. With Peter Roopnarine of the California Academy of Sciences and Ken Angielczyk of the Field Museum, I study the dynamics of extinction in terrestrial ecosystems during the Permian. Using models of Permian food webs, we explore how the extinction of primary producers (e.g. green plants) could have led to the collapse of terrestrial ecosystems. More generally, we study factors leading to stability or instability in ecosystems.

More information:   Publications   |   Lab members and collaborators   |   Grant funding   |   Outreach   |   Media coverage   |   Talks

Reearch profiles:   ResearchGate   |   Google Scholar   |   ORCID

Other areas of interest:

Statistical graphics and visualization. I am interested in how to effectively visualize high-dimensional datasets using graphical methods such as parallel axis plots and data image plots, and more generally in principles of effective graphical representation and communication.

Statistical methods in baseball research, also known as sabermetrics. I am interested in the analysis of managerial strategies (featured in the New York Times and the Philadelphia Inquirer; also see here for additional media coverage). My MS thesis was on a Markov Chain model for baseball lineups and player evaluation, with advisor Michael Stein. Here is a graphic I did with RIch Wicentowski of the Swarthmore Computer Science department on the history of the Yankees, and an interview on the growing use of statistical analysis in baseball.

Opportunities for students: I am planning to have two openings for undergraduate student researchers for each of the next two upcoming summers (2016-2017). These are paid positions funded by an NSF grant. I am also open to supervising projects on statistical paleontology during the school year for course credit (independent study/directed reading). Please email me if you are interested. Due to funding restrictions, eligibility is usually limited to Swarthmore students. The preferred prerequisites are Stat 61 and CS 21 (or equivalent), but some combination of Stat 11, Stat 31, Bio 2, or other experience may suffice as well. No paleontology background is necessary. Learn more about projects and publications by previous students.


Courses at Swarthmore College
Stat 1: Statistical Thinking
Stat 11: Statistical Methods I
Stat 21: Statistical Methods II
Stat 31: Data Analysis and Visualizaiton (now Stat 21)
Stat 41: Quantitative Paleobiology (new course for Spring 2017)
Stat 61: Mathematical Statistics I
Stat 111: Mathematical Statistics II seminar

View information on my previous courses and course evaluations at Stanford, Harvard, Williams, and The University of Chicago.

I was awarded the 2008 Waller Education Award from the American Statistical Association for innovation in the instruction of elementary statistics.

Watch a video of my talk at TEDxSwarthmore.

Requesting a letter of recommendation from me? Please read this page first.

About me

Positions held
I am a Professor of Statistics at Swarthmore College in the Department of Mathematics and Statistics. I have also taught at The University of Chicago in the Department of Statistics, Williams College in the Department of Mathematics, Harvard University in the Department of Statistics, and Stanford University in the Department of Geological and Environmental Sciences. I also worked as a programmer for Data Description, Inc., working on Data Desk statistical software.

I went to college at Cornell University and majored in Statistics and Biometry. I went to graduate school at The University of Chicago in the Department of Statistics.

Trivia: What do Stanford, Swarthmore, Harvard, Chicago, and Cornell have in common? (Hint: think team nicknames.)

Music. One of my hobbies is music composition and songwriting. Some musicians/composers I like are Steve Reich, John Adams, Aaron Copland, The Corrs (read an interview I did with Sharon Corr: Part 1, Part 2), Imogen Heap, October Project, Joe Jackson, and Chuck Mangione. Some representative pieces of mine include a Sextet for Percussion that was performed at Swarthmore (photo at left) and at Kean University Music Conservatory, and a setting of the WWI poem "In Flanders Fields". I am also interested in music that uses the melody inherent in speech, such as in this piece inspired by the Parkland and Sutherland Springs mass shootings.

Trivia. I was a contestant on Jeopardy! in 1996. I was an alternate on Who Wants to be a Millionaire in 1999 but didn't appear on the show. (I did get to meet Regis and John Carpenter. the first million-dollar winner, who was on my taping.) I played in quiz bowl while I was a student at Cornell and Chicago, and captained the University of Chicago College Bowl team, the NAQT 1997 International Champions.

Contact info

Fall 2018 Office Hours
Mondays and Wednesdays 3:00-4:30
or by appointment, or just drop in any time my door is open
Science Center 159

s c w a n g [at] s w a r t h m o r e [dot] e d u 
@scwang251 Follow @scwang251

Mailing address
Department of Mathematics and Statistics
Swarthmore College
500 College Ave
Swarthmore, PA, 19081

voice: (610) 690-5769
fax: (610) 690-6854

Last update: September 5, 2018