RIP Bob May, 1936-2020

Very sad news: Bob May passed away yesterday. He was 84.

“Who’s the greatest ecologist in history?” isn’t a question worth taking seriously, except as a conversation starter. But Bob May is among those who’d come up in any conversation started by that prompt. Put simply, Bob May invented large chunks of modern ecology–both the questions we ask, and the standard approaches we use to answer those questions and others. He was part of the generation of now-household names who turned ecology from a peripheral, backwater discipline to a core biological discipline.

Bob May was born in Australia. After spending over a decade as a physics prof at the University of Sydney, he moved to Princeton and switched to ecology in 1972. He immediately made a massive impact. He began working on the question of when a “complex” community–meaning a community comprised of many species, all interacting strongly with one another–will be stable. In the simplest baseline case, the shocking answer was, basically, “never”. That is, increasing complexity is actually destabilizing in the simplest baseline case. The answer was shocking because it was completely contrary to the strongly-held intuitions of ecologists at the time. The notion that diversity or “complexity” begets stability dates back at least to Charles Elton. But according to May, that notion is wrong (or at least, so vague it might as well be wrong). Far from promoting the “balance of Nature”, high species richness and strong interspecific interactions actually inhibit that balance. Bob May first published that insight in a 1972 Nature paper, and then fleshed it out with related results in a now-classic Princeton Monograph, Stability and Complexity in Model Ecosystems. As of this writing, Stability and Complexity in Model Ecosystems has been cited over 8700 times, according to Google Scholar. One could fairly describe much of the subsequent 40+ years of theoretical and empirical community ecology research as an attempt to find ways around May’s result. Either additional biological realism that would reverse or overcome the destabilizing effects of increasing complexity. Or else other ways of defining “complexity” and “stability“, for which Elton’s intuition still holds. That the attempt has had successes doesn’t diminish the importance of May’s original result in the slightest. We wouldn’t have even known that that 40+ year research program needed doing, if not for Bob May.

Leaving aside the specific results in Stability and Complexity in Model Ecosystems, the approach it took also was massively influential. Along with Robert MacArthur, Richard Levins, and a few others, Bob May helped make ecology safe for what he called “strategic” models. Simple mathematical models that deliberately strip ecology down to the bare essentials, in order to capture the essence of one key phenomenon. The empirical research inspired by strategic models has something of a mixed track record. The history of ecology is littered with weak tests of model’s like May’s stability-complexity model. (Including from me! I think Fox and McGrady-Steed 2002 JAE was a creative attempt to test May’s idea, but looking back even I don’t find it especially convincing.) But that probably just illustrates how original and inspirational May’s work was.

Now, here’s a thing: Stability and Complexity in Model Ecosystems is probably only Bob May’s third most important achievement.

Number two is probably chaos. Bob May wasn’t the first to discover chaos–roughly, deterministic dynamics that are extremely sensitive to initial conditions, and so are effectively unpredictable more than a short time into the future. But as far as I know, his was the first work on chaos to attract widespread attention in biology. In 1976, May shocked the world by showing that the discrete time logistic equation–the dead-simplest model of density dependent population growth–could exhibit chaotic population dynamics for some parameter values (basically, sufficiently high r). His Nature paper reporting this result, “Simple mathematical models with very complicated dynamics”, has been cited over 7500 times. That paper led to a massive explosion of interest in what came to be known as “chaos theory”, ably chronicled in James Gleick’s popular book Chaos. The search for chaotic population dynamics in ecology bore fruit in the lab; whether there are any examples in nature remains somewhat debatable. But again, that doesn’t take away from May’s work in the slightest. We wouldn’t have even known to look for chaotic dynamics if it hadn’t been for Bob May.

And number one is probably his pioneering work with Roy Anderson, modeling the dynamics of infectious diseases. The first part of Anderson & May’s two-part 1979 Nature paper, “The population biology of infectious diseases”, has been cited over 3200 times. It’s the foundation of essentially all subsequent disease ecology and epidemiological modeling. Their 1992 book, Infectious Diseases of Humans: Dynamics and Control is a standard reference and has been cited over 12,000 times. It’s one of the odd coincidences of history that Bob May passed away during a coronavirus pandemic that has highlighted once again the tremendous importance of infectious disease modeling.

May wrote many other papers and was involved in several other books. Many of which have themselves been cited thousands of times, and which would be crowning career achievements for most any ecologist. Here’s his Google Scholar page.

During his illustrious career, Bob May held faculty positions at several of the world’s most prestigious universities, and won more or less every honor available to an ecologist. His most notable honors include the ESA’s MacArthur Award, the 1996 Crafoord Prize (the closest thing ecology has to the Nobel Prize), and the 2007 Copley Medal from the Royal Society of London. He was a Fellow of the Royal Society of London (and later its President), and an honorary or foreign fellow of several other national scientific academies. In 2001 he was created a life peer (choosing the title Baron May of Oxford), one of the first 15 “people’s peers” to be elevated to the UK’s House of Lords in this manner. He also served as Chief Science Adviser to the UK government from 1995-2000.

It was shortly after his term as Chief Science Adviser ended that I met him for the first and only time. He spoke on UK government science policy at Silwood Park, where I was a postdoc. Afterwards, I asked him to sign my copy of Stability and Complexity in Model Ecosystems. I felt a bit embarrassed, but he was very kind and happy to sign. I got the feeling I was far from the first junior ecologist to ask him to do this.

I’m not the only Dynamic Ecologist influenced by Bob May. Here’s Meghan’s old post on how she finds herself rereading Anderson & May (1979) over and over again, discovering new insights every time.

Having only met Bob May once, I have no personal memories to share. He was widely admired and famously competitive (even at croquet). Perhaps those who knew him will share their memories in the comments.

I’ve written before about feeling like the generation of ecologists I “grew up” admiring in grad school is now passing away. With Bob May’s passing, I feel it even more keenly. I don’t have any special connection to him, I’m just one of many, many ecologists he influenced. Indeed, “influence” doesn’t really do it justice. Bob May’s influence on ecology is ongoing in the same way that the sea’s influence on fish is ongoing. Rest in peace, Bob. You will be greatly missed. But your legacy lives on.

I will add links to obituaries and remembrances of Bob May as I find them; please share them in the comments.

May’s 2005 valedictory address as President of the Royal Society of London

May’s 2012 lecture on beauty and truth in mathematics and science

May’s 2012 lecture on complexity and stability in the financial system

The Life Scientific (2012 BBC radio interview)

Bob May on Desert Island Discs

Guardian news story

NY Times obituary

Guardian obituary

Telegraph obituary

The Times obituary

LiveScience obituary

Nature obituary

Science obituary

Imperial College London tribute

Santa Fe Institute tribute

The Silwood Circle is a history book about Bob May and other influential ecologists associated with Imperial College London’s Silwood Park campus from the 1970s onward. Here’s my review.

17 thoughts on “RIP Bob May, 1936-2020

  1. I did not know Bob well, but he was the scientific editor of both my books, The Theory of Sex Allocation (1982) and Life History Invariants (1993). Yes, he was famously competitive, but also immensely supportive and kind. He wrote me several pages of detailed scientific comments on the submitted draft of the 93 book, a manuscript he wanted for the Oxford Ecology Series after Princeton U Press first turned it down. RIP Bob, You will be greatly missed indeed.

  2. I shared a room with Bob a few times in meetings but only once had a proper one-to-one conversation about science. Rather rashly I disagreed with him on one point. Bob rebutted my argument calmly, firmly and authoritatively, managing to do so without humiliating me in front of my colleagues. Needless to say, by the end of our chat, I agreed with Bob.

  3. Indeed I feel the same about a non-person connection and admiration. Even living in the same city for a short time, I never had the opportunity (or the gumption to ask for one) to meet him. The head of my research group was much closer to him, and shared this wonderful and short tribute this morning with us:

    “Dear All,

    I just heard the very sad news that Robert (Bob) May passed away yesterday. He was a world leader in mathematical biology (specifically mathematical ecology) with numerous prizes and
    honours. He was a pioneer of chaos theory. He was a brilliant speaker, very charismatic, very witty and funny.
    I remember him chairing a conference once where the speaker, who had a very sore throat, just would not stop talking after the time was up. After several attempts at trying to silence him, Bob nimbly snatched the water glass from the speaker, who then had to stop because he literally could not speak.

    The world is most certainly a less colourful place without Bob.

    Philip [Maini]”

  4. Jeremy has, in my opinion, hit all the high spots … though May’s work with others (including Dave Tilman) on the concept of an extinction debt and the counter-intuitive insights that provided and which remain to be fully tested should really be mentioned. The importance of his work with Roy Anderson on the ecology of infectious diseases also cannot be overestimated. It helped lead Anderson and his “A-Team” at Imperial College to a very rapid, very detailed, very accurate, spatially structured model for the spread of foot-and-mouth disease during the UK outbreak in 2001, incorporating various counter-measures. Based on that model, the UK government adopted – in a rare moment of political courage which we should all remember – their recommendation for ring-culling, for slaughtering animals on adjacent farms that had no animals yet demonstrating symptoms. Troops had to be called out to do this, but the analysis showed that that policy saved tens of millions of domestic animals and brought the outbreak under control rapidly. Neil Ferguson, a member of the “A-Team”, is now the leader of a similar group at Imperial College, working on a spatially structured model for the spread of COVID-19 in the UK and the USA … which model seized the attention of leaders in Europe and (ultimately) the US for its dire implications.

    I had the privilege, as a grad student, of serving as Bob’s first TA, in his then new course on ecology, and of having nearly weekly lunches with him, my advisor John Terborgh, and Henry Horn. I learned a great deal from those interchanges, and Bob was always a sparkling light and source of insight. I will always treasure those days. Bob’s record speaks for itself, and he is truly a member of Ecology’s Pantheon. But he did have his failings. He was our top theoretical ecologist, but he didn’t necessarily understand the details (crucial details!) of some systems; I was painfully aware of that shortcoming in some of his forays in plant ecology. And Jeremy mentions that Bob was famously competitive. Ha – you have no idea! We often played tennis together … I think not least because he liked to (frequently) beat me at 22 while he was 36!!

    It’s a sad day for ecology, for Bob’s former colleagues, and for his family. Thanks, Jeremy, for you splendid remembrance of him.

    • “May’s work with others (including Dave Tilman) on the concept of an extinction debt and the counter-intuitive insights that provided and which remain to be fully tested should really be mentioned. ”

      Yes! That was one the papers I was thinking of that would be crowning achievements for just about anyone else, but are really just footnotes to Bob May’s career.

      Thanks for bringing up Anderson & May’s role in the response to the foot & mouth outbreak. I lived through that as a postdoc in the UK. I now do a lecture on that case to open my undergrad course on mathematical modeling in ecology. Sadly, I should probably replace it with a lecture on COVID-19 now…

  5. Bob May was indeed a massively influential and marvelously accomplished scientist. I am old enough to have been a grad student when he first appeared in ecology in the early 1970s. One of his first ecological papers considered time lags in population models. My first paper, in 1972, was a crude (by present standards) simulation study of time lags in population models. After I read his paper, I sent him a copy of mine. He wrote back, saying he was sorry not to have known of my paper to cite it. Which is cool, of course, although he was not then the famous person he eventually became. But what’s important is the “by present standards” part of my description. May helped create those standards. Over and over again he took theoretical models, pared them down to capture the essential aspects of some problem, and used the array of mathematical tools that we now employ automatically — phase portraits, isoclines, stability analysis, what we now call dynamical systems theory… — so that is now that way that we largely think. It is so much a part of our intellectual landscape that it’s easy to forget that theoretical ecology wasn’t always like that.

    Anecdotes about Bob’s competitiveness abound. Here’s one. At a symposium in the early 1980s, he and I were sitting close by doing what one did then: putting finishing touches on our overhead transparencies. Someone made some comment to me that led me to wave at them the pack of colored markers that I was using. Without saying anything, Bob immediately waved his pack, which contained at least twice as many colors as mine.

    Thank you to Jeremy for the remembrance.

  6. Yesterday I was chatting online with someone about this sad news, and he aptly articulated what we realized was our shared pleasure of demonstrating the discrete logistic model to Introductory Ecology classes. You slowly raise r, and things start to get all jaggedy. Much of the class looks on blankly as usual; however, there’s always at least a few who are a combination of delighted and amazed as the implications of chaos dawn on them. It’s one of the best and easiest ‘ecology personality tests’ I can think of, and it’s thanks to Robert May.

    Thanks for the great post on such an amazingly influential individual!

    • Yeah, walking students through the discrete time logistic as r increases is the first cool thing they see in my population ecology class (after introductory/review classes on exponential and geometric growth and the continuous time logistic, all of which are boring). It’s a great class to teach. Gives them new intuitions and generalizable insights (e.g., the combination of time lags and density dependence is destabilizing). It’s super-fun–they all come away understanding what the heck Ian Malcolm was on about in Jurassic Park. And it’s just amazing and profound. Looking at the bifurcation diagram of the discrete time logistic is like looking at the stars. Or at a great magic trick that remains great even when you know how it’s done.

  7. see also, his valedictory address as President of Roy Soc. Starts with brief autobiography, but then turns to the problem of sustaining cooperation in tragedy-of-commons situations, which he fingers as the outstanding intellectual challenge of this century. (Rightly, I think.)

    He was a truly great and creative scientist. Only ever had one extended conversation with him. He was alarmingly quick-thinking, and cut straight to big questions. Among other things he asked why plant ecology was so uninspired. (Or words to that effect. This was sometime around 1990 I think.) Tried ecological strategy ideas on him, but he didn’t seem convinced.

  8. I knew him from when I was on the staff at Silwood Park. My office at one time was in the Manor House and overlooked the infamous Croquet Lawn, so I often saw the ecological greats in action. As you say, Bob was a very gifted man, but he was not a field ecologist by any means 🙂 I say this with no disrespect, but to emphasise that ecology is a broad church. I had the privilege to be on the council of the British Ecological Society when he was President. The possibility of changing the name of society newsletter, then known as The Bulletin came up. I suggested Quadrat as I thought that this was a good description of something that enabled the society to collect views and disseminate them. Bob looked at me quizzically and asked “What’s a quadrat?” I was a bit nonplussed and explained. Bob replied, and for a change not with his favourite descriptor of people he had no time for (f**kwit in case you never heard him in action) – I was always waiting for him to accidentally use the term when he was Chief Science Officer and being interviewed on the TV or radio) “Nope, we can’t call it something I’ve never heard of” and so it remained the Bulletin until a few years ago when it became The Niche, which I have to admit, is a much better name.

    He will be sorely missed.

  9. I think that another pivotal contribution was: May RM. 1977. Thresholds and breakpoints in ecosystems with a multiplicity of stable states. Nature 269:471–7.

    The basic idea of the singular perturbation approach in ecology was first described in this paper. This was used later in Ludwig and others (1978) to characterize the recurrent outbreaks of insects and very frenquently now to discuss theoretical problems in aquatic ecosystems (see the work from Beatrix Beisner, Marten Scheffer, Egbert Van Nes and others…) and also terrestrial ones.

  10. He was generous to me. I remember as a doctoral student I didn’t know how to formally prove a relationship that I could see was true (about the behavior of vital rates in non-homogeneous populations). I could see that this relationship had been overlooked in a (then) recent article in Science, and that this mattered to the article’s conclusions. I had written a comment to the journal but wanted to prove it too. I asked around but no one in my department (Plant Sciences) could help. Someone advised me to write to Bob May in Zoology and he replied the next day, agreeing with my assessment, commenting on my “unusual notation” (some of which we maintained), and also providing a clear outline of a proof.
    We then developed a full article. When Science suggested that my short critical comment was incorrect he also phoned the unfortunate editor to point out their error. On the longer article where we proved the concept he insisted I was lead author and gave encouraging comments and suggestions (often brief notes) and advice at each stage as it progressed. The resulting article (in Journal of Ecology) certainly helped my visibility (“oh you’re the guy who published with Prof’ May right?” etc).

  11. A further thought on Bob May: there’s a stereotype, with not a little basis in fact, about theoretical physicists naively thinking that all other disciplines would benefit greatly if only some theoretical physicists would move into those disciplines and make some simple mathematical models. Bob May was the positive version of that negative stereotype. His example shows that, if the *right* theoretical physicist moves into the *right* non-physics discipline, then yes, that discipline actually can make a leap forward it wouldn’t otherwise have made.

    I have an old post on how “techniques aren’t powerful, scientists are” ( It’s about how what matters in science mostly isn’t the technique or approach per se, but the person using it. I didn’t use Bob May as an illustrative example, but in retrospect I wish I had, because he was just about the best possible illustration.

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