Robert R. Sokal 1926-2012

by Greg Mayer

Robert R. Sokal,  Distinguished Professor Emeritus of Ecology and Evolution at the State University of New York at Stony Brook, died at the age of 86 on April 9. During his long career he made distinguished contributions to evolutionary biology, systematics, human population genetics, and statistics, and generations of biologists have learned the principles and practices of statistical inference from the textbook he wrote with Jim Rohlf, Biometry (first edition 1969; fourth edition 2011). It was my privilege to be a student of his as an undergraduate at Stony Brook.

Robert R. Sokal in 1964 (courtesy the late Robert R. Sokal, via Joe Felsenstein, from Panda's Thumb)

Mike Bell has written a fine summary of his career at the Stony Brook Ecology & Evolution website, and Joe Felsenstein also has memorialized him at Panda’s Thumb (read the comments there, too). His life story was just as, if not more, interesting than his scientific career. Born into a Jewish family in Vienna, his family fled the Nazis in 1939, and found refuge in Shanghai, China. There, he attended college, and met his future wife, Julie. They came to the United States after the war ended, and remained here. Their story, known in general terms to all at Stony Brook, was chronicled in the book Letzte Zuflucht Schanghai: Die Liebesgeschichte von Robert Reuven Sokal und Julie Chenchu Yang by Stefan Schomann (click on the title for pictures from their time in China).

He will be perhaps best remembered for his contributions to, and insistence on, rigorous, quantitative reasoning in all aspects of biology, and in helping to usher in the age of computer-based analysis of biological data. In systematics, he pioneered quantitative techniques in both phylogeny reconstruction and the assessment of similarities and differences. The latter, which he pioneered with P.H.A. Sneath, became known as numerical taxonomy. Sokal and Sneath argued that knowledge of phylogeny was not fundamental for the classificatory purposes of taxonomy, which they thought should be based on overall resemblance (an approach known as phenetics). This approach to systematics has not prevailed, but the methods developed have proved of great value throughout biology, including phylogenetics. Although he thought evolutionary considerations should not rule taxonomy, he was always devoted to the study of evolutionary questions, first in aphids, then weevils (a word he consciously strove to avoid saying, because of how it came out from a native German-speaker– something like “veevels”), then man, among other subjects. Ironically, it was some of his opponents in the taxonomic debate (the so-called transformed cladists) who seemed to lose interest in evolution, embracing a sort of Platonic idealism as the basis for what were supposedly phylogenetic methods.

At Stony Brook, he was a towering figure, always impeccably dressed in coat and tie, and with an Old World dignity and reserve, the latter reflected in the fact that, unlike all the other professors, he was known to graduate students as “Dr. Sokal”, until the students had gotten their Ph.D.’s.  (There was a weekly Friday afternoon social event called the “BS”, which initials might have various meanings; officially it was the “Beer Social”, but it was rumored that it had those initials so that graduate students could refer to “Bob Sokal” before getting their degrees.) He was also superbly disciplined: on a number of occasions, a hallway conversation with him ended as we approached the elevators, because he always took the six floors of stairs down, as it was a way to regularly exercise without an interruption in his other work. But he was witty, open to discussion, and generous with his time, even for an undergraduate.

For first year Ecology & Evolution (and some other) graduate students, his biometry class was, quite literally, a rite of passage: successful students were inducted in to the “Loyal Order of Normal Deviates”, whose hymn was “Freedom By Degrees”. I was fortunate to be able to take the class as an undergraduate in my senior year (fall 1978). The second edition of Biometry was in the works, and we received the revised text in xerox. As much for his accomplishments as a researcher, he should also be recognized for his accomplishments as a teacher, both in the classroom, and through his book, which I found to be perhaps the most readable self-teaching tool I have ever encountered. I have used it (or it’s shorter version, Introduction to Biostatistics or “Baby Biometry”) for 20 years, and plan to keep using it in future classes. But last week it was my sad duty to tell my class that they are the last to use it while Dr. Sokal was alive.

14 thoughts on “Robert R. Sokal 1926-2012

  1. I’ve had my say at Panda’s Thumb, but let me just add that Bob (who I could call Bob because I wasn’t ever a student in his department) was polite but could be prickly in defense of his views on classification. I think he was saddened that those views did not win out among taxonomists. But he did give the numerically-challeneged senior professors of the Mayr-Simpson school a run for their money. And he gave the phylogenetic systematists a term of abuse, “phenetic”. Actually phenetics is simply one possible position on classification, but it is considered an insult by many to call someone a pheneticist. Even when they are.

    He and Peter Sneath were the major force in getting work on clustering the attention it deserved. Remember that when you see a gene expression “heat map” with clustering trees along the side. Their work was not only foundational, it is being honored by being reinvented by genomicists as we speak.

    Primarily, he was an operationalist and (as Greg has said) passionate about using numerical approaches. He was actually somewhat model-averse — he did not try to derive his clustering methods from assumed models, but hoped that they would be validated empirically.

    Whether you agreed with Bob or not, he had a big effect on biology. And he was always interesting to be around.

    1. Joe– Thanks for commenting here. I’d tried originally to post a few thoughts as a comment on your piece at Panda’s Thumb, but I was prevented because my WordPress login was not recognized, so I decided to do a post here. Characterizing his taxonomic views as operationalist is exactly correct. For him, relationship was defined by the algorithmic procedures used to create the dendrogram.


  2. PS, the proper credit for the photo is that it is courtesy of the late Robert Sokal. He sent it to me when I asked him for a photo from that ers to use in the historical chapter of my book.

    1. Photo credit now updated– thanks! I hadn’t recognized it from your book.


  3. I see this isn’t a very crowded comments section, but I was really glad to see this appreciation on your website. As a historian of science, I really appreciate how important Sokal’s work was in getting quantitative and computer-based methods more accepted in biology and allied disciplines. I study the history of paleontology, and I’ve found many ways in which his work–both Biometry and a number of papers published in Systematic Zoology–really had an influence on the quantitative turn paleobiology took in the 1970s. Many paleontologists learned about factor analysis, for example, by reading Sokal and Rohlf, long before there were primers available for those techniques in their own field.

    He really was a pioneer, and there’s a danger that people will forget about his importance because his numerical taxonomy didn’t win out. That would be a real shame, since it would ignore the real visionary importance of his approach. And it’s also a good lesson in why it’s way too simplistic to treat history as a story of “winners and losers”…

    1. Lots of important or famous figures of their day get forgotten, and some of them are rediscovered by people like yourself who study the history of science, so I am sure one day there will be a Phd student who writes a thesis about his importance!

      Thank to Greg and Joe for illuminating something of the inner workings of academic disagreement. Does disagreement help fuel research by making people look for new evidence?

      1. Sokal and Snrath and the conflict between schools of phenetic, phylogenetic, and evolutionary systematists have already been the subject of a major study in the history of science: David Hull’s 1988 book Science as a Process: An Evolutionary Account of the Social and Conceptual Development of Science, The conflict among schools of classification is one of two major examples covered extensively in that book, with Sokal and Sneath major players in the story.

        So Bob has been the subject, not merely of a Ph.D. thesis. but of a major work by a notable historian of science.

        1. Yes, Hull’s book is an excellent place to learn more about Sokal and the numerical taxonomy movement in general. Joel Hagen has also written a really excellent paper on the subject: “The Statistical Frame of Mind in Systematic Biology from Quantitative Zoology to Biometry,” Journal of the History of Biology 36 (2003).

  4. In the latter decades of the 20th Century, anyone who earned a degree in the biological sciences, knew of Dr. Sokal… if they were paying attention.
    He gave biology a hardcore rep.

  5. Born into a Jewish family in Vienna, his family fled the Nazis.

    How often has this been said of great scientists of Jewish origin from Vienna. I’m not claiming any specific racial position here, just that the cultural environment in pre-WWII Vienna must have been outstanding.

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