In a landmark chapter published in 1972 in a book called Models in Paleobiology, Niles Eldredge and Stephen Jay Gould proposed, based on their observations of the fossil record, that evolution proceeds in short bursts of change separated by long periods of stasis, a theory they called “Punctuated Equilbria.” In 2016, 44 years after the publication of the paper, I spoke to Nile Eldredge about the origins of this theory, his collaboration with Stephen Jay Gould, and the reception and impact of this theory on our understanding of evolution.
Citation: Gould, N. E. S. J., & Eldredge, N. (1972). Punctuated equilibria: an alternative to phyletic gradualism. Models in Paleobiology, 82-115, edited by Schopf, TJM Freeman, Cooper & Co, San Francisco.
Date of interview: 7th December 2016 (via Skype)
Hari Sridhar: I’d like to start by asking you a little bit about the origins of this idea. I looked at your publication profile and realized that this came soon after your PhD on this trilobite called Phacops. What led you to this view of evolution at this time?
Niles Eldredge: Well, actually, the story I normally tell, and I think I still agree with it, is that a bunch of us in the 1960s, at Columbia, wanted to get evolutionary, even though we were enrolled in a geology program, which is where invertebrate palaeontology resides usually. We knew that the invertebrate fossil record is immensely richer than the vertebrate fossil record. And there were statistical tools – computers and multivariate analysis – available. So it struck a number of us that, when we were doing our PhDs, to take advantage of this technology and to use the multi-variate approaches and so forth. Let’s see if we could document evolution. But the thing is there aren’t rich fossil records all over the place, I mean, with thousands of specimens and not just, you know, a couple of bones in there, that kind of thing. As invertebrate palaeontologists, we knew we could identify sequences of fossils occurring in sufficient numbers though time and over space to sample (if chosen wisely)—to come to grips more accurately with what the patterns of evolution actually look like in the fossil record. So, I think the expectation, certainly in my mind and probably in everybody else’s, was that it would be more or less, as we were reading, not so much of Darwin, but Simpson, Mayr and Dobzhansky, but talking basically about the theme that was palaeontologist’s favourite, ever since Darwin, which is that life evolves gradually. And that we would document some terrific examples of just slow, gradual, evolutionary change and just see what was out there. That was the idea.
The problem was that things, seemingly, were not evolving! They weren’t changing. Honest to god, you look at my trilobites: 6-8 million years, we understand now, the stratigraphic record of this particular group that I was looking at, in eastern North America, the Devonian, there’s very, very little change; they all look the same. And if you do the statistics on them, there’s very little change. In some instances, you get a little bit of a shift, but there are always reverses, you know, that type of thing. So, yeah, the short answer to your question is, it was out of desperation: I needed to find some signs of evolution!. And I realized that a way out of this might be the geographic variation, the geographic isolation, which Dobzhansky basically pioneered thinking about in the 1930s—the generation before me and my fellow students came along in the 1960s. But Mayr is, of course, well known for having developed or perhaps developing even further the work that Dobzhanksy did.
So I tried to put those two worlds together. After speciation, Dobzhansky said, there will be gradual change through time. So he had a hybrid sort of a vision. But we were faced with this sort of intransigent stability in our samples. And it wasn’t just my stuff; everybody was finding this, and looking at it and being honest. So, as you know, the lack of readily seen examples of slow steady gradual evolution of species in the fossil record was attributed to poor data—rather than as a signal of the way things actually are. Going back to Darwin the fossil record was proclaimed to be inadequate. I viewed the geographic business as a salvation—as a way of getting out of this trap of not finding any evolution at all.
HS: As a PhD student, was it worrying to you that you were not finding any variation in your data?
NE: Oh, my god, yes! I remember over the years telling audiences. You know, basically, what you’re supposed to do is not only frame and pursue an original scientific study, but you’re supposed to get what are construed as positive results. And I was getting nothing but negatives. I remember my worst moment was, actually, with my wife, we were in Michigan, the state of Michigan, collecting fossils, Our clothes were dirty, so we went to a laundromat, washed our clothes, and I pulled a specimen out of my pocket – which was a particularly nice one and very hard, so I was just carrying it around – and I just couldn’t tell it from the ones in New York. And, you know, it turns out it wasn’t even the same species – you have to look at the eyes, so forth. But these things all basically look alike. You know, so here I am halfway across the United States, or a third of the way across the United States, in a different segment of time, but it’s just the same as what I was familiar with back in New York. And my heart sank, it really did. I thought I wouldn’t be able to get a PhD because I wasn’t seeing any evolution.
HS: Did you collect from all over the United States for your PhD?
NE: Well, this inland sea with this fauna is basically in eastern New York and it extends all the way down through the Appalachian Mountains. And then it goes as far west as Iowa. I don’t think that fauna has been found any further west than Iowa. But the rocks are thinner, the amount of time is spottier, when you collect in the midwest. The thicker sequences in the East give you a much more complete record. But then you see these things in Michigan and Iowa and Indiana. These are beautiful fossils. So that’s it. I collected everywhere that they were known to have existed.
HS: Before I ask you more about this chapter, I just want to step back a bit and ask you how you got interested in fossils and in trilobites particularly.
NE: Yeah, that’s interesting. In high school, I was not known as a scientist. I was studying languages and I went to college expecting to study languages but I was intrigued by the idea of evolution. And I did read some books in high school about evolution. At that time, we had to take a science requirement, a science course. Everybody said take geology because it’s easy. And I fell in love with it, basically. I was also looking at anthropology, but it was easier to collect fossils, it turns out, than to speak to people. I went down to Brazil and did a study in anthropology and learned Portuguese and so forth, but I was embarrassed to ask people there about their personal life and things like that. So I found fossils. I don’t know… I was studying Latin as a beginning college student, but I fell in love with fossils in my second semester of introductory geology, and I remembered my interest in evolution. So that was it. It was just already sort of latent there. But I just thought it was very romantic to collect fossils and knowing how old they are. It was just incredible. So that came, you know, I don’t know, Spring 1963 maybe, when I went on my first field trip and collected fossils with a geology class from Columbia. I had something else to say about that. Tell me the question, again, the precise question.
HS: I also wanted to know how you got interested in trilobites.
NE: The trilobites. I started hanging around with graduate students that had come in, in 1964…no they came in 63. One of them was Steve Gould. The other important one in my life was Bud Rollins, and he was studying snails. And one of the faculty members that he worked with was Roger Batten; he was also studying snails. So I too started studying snails. I actually wrote about them, several papers, and my wife became a very good collector of fossil snails. Snails have a simple morphology. They grow sort of geometrically and coil around and so forth. The shells are not complex, but they’re beautiful. So, this friend of mine, Bud Rollins, said, well, you know – he is the snail guy – you should consider trilobites, because they’re complex. And I can see that. I’m looking at a picture of trilobites right now, in my room that I’m sitting in, and these ones have 11 thoracic segments, they can roll up, they have a shield for a tail made out of fused segments and they’ve got complex eyes. There’s all sorts of stuff. There’s all sorts of body parts that preserve commonly. So, you know, they would give me more characters, and I was already doing this multivariate stuff, so I could see a ton of characters there that I could measure and so forth;whereas on a snail, not so many. So I think from an analytic point of view, that’s why I jumped over to trilobites. But everybody loves trilobites anyway. They have eyes, they actually look like a living creature more than almost anything I can find in the fossil record. So it was a combination of those things. My wife was very disappointed because she loves snails better.
HS: Who was your PhD supervisor?
NE: It was complicated. We had three palaeontologists. At Columbia, there was one palaeontologist, John Imbrie, who was my first teacher, and he was a brilliant person and a great lecturer. But he was more interested in ecology, to be honest, and not phylogenetics and not evolution. I got a grant in the summer of 1964, to work at the American Museum of Natural History, and I was working with a guy named Roger Batten and he was the snail guy and I was doing snails with him. But the real figurehead of all of this was Norman D. Newell, who was the one who really pioneered the realization that mass extinctions do happen and worked real hard in the middle part of the 20th century to get those respected as extremely important natural phenomena in the history of life on Earth. And so when it looked like I was actually coming up with something new, Norman Newell became my official sponsor. But these other guys were also extremely important, as well as the graduate students – Steve Gould, Bud Rollins and a few other people.
HS: In the 1971 paper in Evolution you were already talking about this idea. But was this something that you had already discussed in your PhD thesis?
NE: Yes. You know what, I just reviewed that history to write my book Eternal Ephemera published in 2015. but the point of the ’71 paper was to show that the Dobzhansky/Mayr concept of geographic speciation is relevant to understanding evolutionary patterns in the fossil record. I did talk about speciation in my PhD Thesis (1969). Yes, it’s in there, but it’s not in a form that is as crystallized and more fully developed as it became in the 71 paper.
HS: How did the collaboration between you and Steve Gould come about, for this ’72 chapter?
NE: Well, he started graduate school at Columbia in 1963. I was a junior, you know, undergraduate, but the new graduate students, there were a bunch of them, and they were all smart. Many of them were interested in evolution and Steve was one of them. Later, when I had become a graduate student in ’65, we had offices adjacent to each other and we talked all the time. He said great things to me like, you know, don’t wait till you’re 60 years old, you’ve got to think theoretically, and be willing to publish early on. And he was publishing things, and I started publishing things a little bit, but nothing like him, at his rate. So that was a tremendous amount of encouragement. We were friends. And then when I came to graduate school we used to go back and forth between the museum and Columbia University, which was about 40 blocks away, but it’s a linear distance and there’s a bus that connects them. So, very often, I was on the bus with Steve, and he could not really contain himself from, just, basically giving an impromptu lecture based on something he had just recently read. I have to say that the connection went to the point where the editor of Natural History magazine said to me, several years after that, that he needed a new columnist and I recommended Steve , because I said, the guy’s never at a loss for words; he always has a story to tell. And that’s what you want, you know. So we were friends, we were social friends, living in the same neck of the woods, in uptown Manhattan, and we saw each other almost daily. He never moved down and took an office at the museum. Some of us, when we were deep into our research, went to the museum as students and worked down there. But nonetheless, I would see him three, four or five times a week. He was two years ahead of me, and he left for a position at Harvard, in 1967, when I was still a student. And so, I don’t know, we stayed in touch, we talked, but not as much, obviously, as we used to. And then one day, I think, he called me up and he said that there was an opportunity to participate…it is a book, these were intended to be a collection of biologically, theoretically oriented papers independently written of each other for inclusion in a compendium. It was an invited paper, is really what it was. And he said there was this project that was being developed by Tom Schopf, who, I guess, was at the University of Chicago at that point. Anyway, Tom, rightly, was looking at the fact that palaeontologists were just describing fossils and they’re not thinking much, or very rigorously, about what they mean. They’re not looking at the issues. So there’s no theory really going on. And he wanted to sort of jump-start a renewal of energy, of thinking theoretically, in palaeontology. That’s why he had this project. There was a symposium at the Geological Society of America, and it was also eventually, this book. And Steve found out about that. We were young, so the network really wasn’t established too well. But Steve was very eager to participate in Tom’s project; he literally told me he had to get into that book. And he wanted either phylogenetics or something to do with the evolution of morphology for his topic. But Michael Ghiselin had already been asked to do the phylogenetics, and Dave Raup did the morphology. And these are good guys, and they wrote good stuff. And Schopf was adamant with Steve, he said, no, you can’t have either one of those topics. And those were his first love, they remained his first love: especially morphology, and, well, not even so much phylogenetics; he was really a morphologist and a good one and a creative thinker in that love of his intellectual life—morphology.
So Steve called me up and said, look – my ’71 paper had not been published yet, but I had sent him a type-script – he says, the only thing that’s evolutionary, really, that they’re offering me is speciation. And he says, I can’t think of a single thing to say other than what you’ve already said in your paper. And he said, so, would you agree to join with me and the two of us could collaborate on a paper under that topic? And so I said, of course. That was a wonderful opportunity and I didn’t think twice about it. And so we agreed to do it. And we agreed that I would write the first draft. And now this has been gone through, not just by me, but also by David Sepkoski who is a historian of science and the son of Jack Sepkoski, one of Steve’s first two graduate students at Harvard. And what Dave pointed out, and it’s true, is that my first draft is in that paper, almost verbatim. Some of the writing was changed just for stylistic purposes. We all know Steve was concerned with stylistic writing, and he integrated that paper very well, but, basically, as I say – because I just looked at this two days ago in my book Eternal Ephemera, what I say about this. I say in the book that Steve basically wrote the beginning, and much of the end. I added some critical stuff to my original ’71 paper. I made one big, huge addition with a discussion of the differential production and survival of species—which laid the ground floor for decades of exploration and analysis of selection of species at the species level, above the level of Darwinian natural selection which works on variation among individuals within breeding populations. But he had things to say also of a theoretical nature at the end. And the beginning is a wonderful summary of what the basic thesis is. And he wrote that, and he wrote some other stuff about the philosophy of science and so on and so forth. The core of that paper is, almost verbatim, what I wrote to him as a draft, you know, as a first draft.
HS: There’s a fairly large section in the chapter describing, both, yours and Steve Gould’s empirical work.
NE: Right, I wrote his stuff. He said to me, you have a copy of my thesis – or actually it was already published as a Harvard bulletin at that point – he said, I think you should take my stuff and interpret it in this way. So I did. There are people who disagree with that, of course. But anyway, I wrote that too; it’s all in that original. I think that’s all available, by the way, all these preliminary versions are available at the American Museum website. It’s been scanned and it’s up.
HS: What’s the story behind the terminology – “punctuated equilibrium”?
NE: Well. This is another thing that surprised me when I reviewed all this stuff a couple of years ago, I always say, and I always said, that Steve invented that term. I still think it’s true. And also “stasis” and also, I guess, “phyletic gradualism.” These are the key phrases that sort of ring bells in people’s minds and are associated with that. And I have found that those words were in my preliminary draft;now, not in the ’71 paper, but in the preliminary draft. But I still do not think that that means that I coined them. I’m convinced that Steve did it. There was a funny thing that happened down the line when Steve started calling it…you know, the title of the paper is Punctuated Equilibria: An Alternative to Phyletic Gradualism. He started calling it “Punctuated Equilibrium“. I don’t know why. I asked him why he changed it. He said, changed what? I said, well, the original thing is “Punctuated Equilibria“. He never gave me an answer. Sometimes you get a little paranoid and think that he was just trying to, I don’t know, rename it to make it more his or something. I don’t know. Because there was a little bit of that as we went down through time. A lot of people still think that it was all his stuff, which naturally I have found irritating over the years from time to time; but not so bad. Anyway, how did it come up? I don’t remember. I think he said we should call it “Punctuated Equilibria” for obvious reasons. It combines the stasis part with the relatively rapid episodes of allopatric speciation. And I swear it had to be Steve. I don’t remember the conversation, probably over the telephone. I don’t remember when he first said that to me, but I’m pretty sure it was he and whatever. It makes sense, you know. To this day, I intensely dislike the term “Punctuated Equilibrium.” The original “Punctuated equilibria” suggests it is meant as a general term, involving many many cases—a common pattern of evolution. The singular form “ium” does not do that work. In any case, around my house, we have always just called it “punk eek.”
HS: Did you give a talk at that meeting?
NE: Oh, here’s what the deal was. We had an arrangement. He says, you get nervous when you give speeches, which, embarrassingly, I have to admit was true. And it was true, basically, for most of my career, I don’t even give speeches anymore. I’m sort of sick of doing them. And he loved getting up on the stage and giving speeches. So he said, I’ll tell you what, here’s what we’ll do. You can be senior author of the paper, which I thought was great. But I (Steve) will be the senior author of the abstract and I will give the talk, because you don’t like giving talks in public. And I said, great, that’s a done deal, because it works for me in many ways, you know. And I already knew at that point, that if you’re a junior author of a paper – and I had no idea that the paper would become as important as it is – but I still thought that if you were a younger person, and you are the junior author, you don’t tend to get much credit, if at all, you know, for the paper. So I was really delighted to have been made the senior author. Before Christmas, we’re going to put an hour and 15 minute video up of all of this stuff (see my YouTube channel film with Stefano Dominici, based on my book Eternal Ephemera), and I’ve recorded towards the end of the video saying that was probably the dumbest thing that Steve ever did, was to make that arrangement. It really was. He came into my office one day, when I had just started work on the staff at the American Museum, and he said, I think – he just burst into speech – I think that I should be the senior author of that paper. And I said, huh, all right. And then we got together later that evening with our wives and went to the movies, saw two Ingmar Bergman movies, And then he was going south with his wife, and he was on the subway platform across from me, and I was with my wife, and we were going north. And I started getting very upset, and I started thinking I made the greatest mistake I’d ever made in my life. Fortunately, he stayed in town and didn’t go back to Harvard right away the next day. He came back into my office the next morning, and I burst out and I said, I should be the senior author like we agreed. He said, all right, fine. All right, fine. So, that’s the way that went.
HS: Do you remember how long it took you to write up the first draft of this paper, and when and where you wrote this up?
NE: Again, I wrote in my office at the American Museum of Natural History. And I think I got onto the assignment, basically, right away. And I don’t think it took me very long because this stuff was all very fresh in my mind. And I had one new set of ideas – the stuff about differential production and survival of species, because if stasis is true, you can’t explain trends really very readily by just selection through time. So what would it be, it would be sorting, what Elisabeth Vrba ended up calling “species sorting” or species selection. It could be either one of those things. I just said, it’s differential production and survival of species. We had a diagram in there to illustrate this concept. I already had that stuff in my head, but I didn’t go ahead and publish it—and added it to the ms I was writing with Steve.
So first I wrote up a summary of the ’71 paper. I had to work on understanding Steve’s empirical work on the Bermuda snails. So it wasn’t just a reprint of the ’71 paper, but it was pretty much the same sort of thing. And so that just sort of flew off the pen. But I think I must have spent a little bit longer time developing this embryonic concept , of species selection/sorting. Anyway, so I think I wrote that pretty quickly, but I must have lingered a bit because I had been doing a lot of thinking about this new issue. So it was pretty fresh in my head, but I had not written it up yet. So it was a great chance to put that in.
HS: The first part of the chapter talks quite a bit about observation and theory, and the problem of everything being thought of in terms of one particular way of looking at one particular picture. You spend quite a bit of the chapter talking about this. Was this because you anticipated that there’s going to be push-back?
NE: Yeah, absolutely. I don’t even particularly agree with absolutely everything that we say about this in there. I think in the paper we were shy about stasis, because, even though it’s an empirical reality, it was such a radical proposal to the palaeontologists and certainly to the evolutionary biology world. In general, it seemed so radical that we were talking about other issues, and so stasis doesn’t actually get mentioned in the paper until about a third of the way through!. In the end, it’s all about that. It is because it exists, that these ideas have to be addressed.
HS: Were the figures in the chapter hand-drawn?
NE: Yeah. I drew the rough one of that one with the species showing differential production and survival, through time. I think it’s the last figure. But I do believe that I got the art department to produce a professional looking version of that. I don’t know what the other ones were. Can you think of some of the other hand-drawn ones?
HS: Well, there is one from Trueman 1922.
NE: That is taken out of Trueman.
HS: I’m not sure if this is also hand-drawn – a standard textbook view of evolution from Moore, Laliker and Fisher.
NE: Exactly. That was the textbook of palaeontology that Columbia was using in those days. It made the point perfectly, but we didn’t draw that.
HS: Since we are on the topic of textbooks, you make the point that textbooks of that time present one view of evolution and that that needs to change. Today would you say that has changed i.e. does punctuated equilibrium get fair representation in textbooks?
NE: Depends on which textbook you’re looking at. But I think, in general, in palaeontology and biology books, we are always there now, but we’re not there exclusively. I mean, they show the old gradualism model. And so, I think at least we got into the textbooks, but we didn’t replace, by any means, the earlier way of looking at things. I’m 73 years old. I haven’t looked at textbooks too much recently, you know.
HS: Neither the book chapter nor the ’77 paper has an Acknowledgements section. Were there other influences, i.e. people you were talking to and discussing these ideas with at that point in time? Also were there any papers that had an influence on your thinking with regard to this topic?
NE: Yeah, well, when I was a graduate student, I was in the elevator once – geology was in the basement and biology was the top floor – ninth floor – and I was holding a reprint copy of Systematics and the Origin of Species – Mayr’s 1942 book. And one of my fellow palaeontology students says, what are you reading that for? So yes, I would say that the biological literature on geographic speciation became very important to me, anyway, as a source of understanding and a source of inspiration. So I read quite a lot of that. Regarding people: we talked to all of our fellow students about what we were doing. Most of them didn’t care so much. You know, they said, that’s nice, and so on. Steve talked to a lot more people in the field than I did, when we got into the late 1960s. Because, as I say, he was already up at Harvard, and so on. But it was more arguing. You know, I’m still disappointed that Dick Lewontin still doesn’t seem to understand. Steve taught a course in evolution with Dick, and he never understood what the whole thing was about. So I felt disappointed that Steve wasn’t able to get Dick, if not to agree, at least to understand. That never happened. But then again, of course, what you always are trying to do is convince the people your age and younger people; older people are not going to change their thinking.
HS: What was Tom Schopf’s reaction to this, when you submitted it to him?
NE: We had to submit 12 copies so he could send them out for review. And I think I found copies of four reviews. And I was sort of surprised to find when I looked at them recently that they are more or less positive reviews. Tom himself hated the paper; absolutely hated it. Steve went off on a very early sabbatical to Oxford, and the paper was in the review process, and he said to me – and of course there was no internet or anything at that point, so it was all done by letter – he said, now it’s your job to make sure you don’t allow people to just come and make demands for changes and so forth that you agreed just to. He said, nobody’s gonna tell us to change. We’re not going to accept anybody’s changes. That’s what he said. And that was his style for the rest of his life. I mean, I used to review his Natural History articles, and I finally gave up because he would never take any suggestions. He just hated being edited. So, I fought with Tom and I got Steve involved, but I hung in there and, actually, in the book (Eternal Ephemera), you’ll see there is a letter I wrote to Tom about this. I reprint the letter in the book, because I was good, I was tough, so I said, we’re not going to change that. I think at one point Tom was accusing us of claiming that we had invented something new We denied that we claimed we’d invented something new. Well, in a way, we sort of did, you know. Schopf also said that we claimed to be the only palaeontologists who’d ever read Ernst Mayr; that was another critical comment. We never said that we were the only ones who had read Ernst Mayr, but we were the only ones who had done anything with those ideas. So, there was a sort of a stalemate. He reluctantly went ahead and published it. He wrote an introduction to that paper and it was pretty not nice. It’s hardly a glowing recommendation!
HS: How was this piece received when it was published? Was it consistent controversial at the time when it came out?
NE: It was. I only had one or two people walk up to me at the annual meetings and say you’re right. Some people said, yeah, you’re right, we knew it all the time. But a lot of people were upset and wrote rejoinders. Phil Gingerich, who is a very good palaeontologist, published a series of papers with data looking at sequences of his mammal tooth evolution in the West. Yeah, there was a gradual trend within a basin, and then it would actually always curve back and get nowhere. But he would then divide them according to the angle of the curves and stuff into different taxa (species), and so on and so forth. He told me years after that, that we were right, he was wrong, because they weren’t looking geographically. These mammals were in these isolated basins in Wyoming and Utah, places like that. And you have to look at the same things in the other basins before you get a whole picture of what’s going on. So he agreed. Jeff Levinton, who’s, I guess, still at Stony Brook – I’m not sure whether he’s retired or not – but he really hated our stuff, and tried all sorts of arguments against this. I don’t think Doug Futuyma liked this too much. And these are people who tended to publish. I mean, I’m a friend of Doug’s, and I’m really a friend of Levinton’s too. Sometimes it was pretty nasty, kind of hard to take, you know. So 20 years, I guess, after we published it, in 1992, Steve said let’s write a little paper for Nature and say, Where are we now? And he went through this usual litany about, you know, people first tell you you’re wrong and then they say, you might be a little bit right, and then they say, we knew it all along. Anyway, Steve was good at those little things. So we wrote a couple of follow up things; nothing intellectually really compelling, but kind of fun. And I would say the same thing about the 1977 paper. When I went over that paper again I remember that he wanted to call it Punctuated Equilibria: The Tempo of Evolution Reconsidered, which meant that he thought it was all about rates. And I said, it’s not about just rates, tempo and mode in the Simpson sense – that was the name of Simpson’s ’44 book: Tempo and Mode in Evolution. On the one hand, by mode, Simpson means how has it happened: issues such as: Is it just phyletic – transformation through time – or is it speciation and geographic? Those were modal questions as far as Simpson was concerned. Steve had dropped that mode thing and I said, no, come on. Really what we’re doing is trying to get a modern sense of geographic speciation injected into this discourse, and if you take away mode and make it all about tempo, that’s really leaving out a lot—most of the novelty of our work. So it’s kind of interesting. Steve didn’t even see that himself, you know, so interesting and a bit frustrating. But he said, sure, so he just wrote mode in right after tempo was there, virtually throughout the paper. That’s basically all I really contributed.
But Steve also saw that the molecular stuff was just beginning to come out, and then we did that, very primitive stuff about proteins and so on, but still, so he was saying that these apparent disparities and rates, you know, you get no change at all, but then you see the molecular stuff changing. He said our contribution to the conversation, and the thinking about this, is going to really help understand what the relationship is between the molecular level and the level of organisms and species. So he had some interesting, early suggestions about that in the ’77 paper, and I thought that was good. I was glad to sort of rediscover that when I was prompted to go back and look at it
HS: When you were writing this up, and when you’re thinking about this, did you anticipate at all that it would become so important and have such a big impact on the field? Now [December 2016] it is cited almost 5000 times.
NE: Well, yeah, by people who largely never read it, because it was in a book. Steve was always very funny about that. And even when they have it, they don’t read it anyway, he said. Well, I thought that of the ideas themselves as purely intellectual ideas. When I was doing the ’71 paper, I thought it was very important, because it was so different from everything else, and yet I thought it was substantially true. So, I did think it was very important. Did I think that the publications of it will become important? I didn’t dare think that and I actually probably was sceptical that they would. In fact, my ’71 paper was hardly read or cited by anybody. That’s why it was terrific to team up with Steve, no matter who did what. That was the way to get noticed, you know, and so that did the idea and me a lot of good, to get that out, and get it read, and get it seen, and get it talked about. I do think that the majority of palaeontologists agree that stasis is not only a reality, but it’s the dominant way things are fossilized. You know, it’s the story of the fossil record. And I think a lot of biologists are comfortable with it too. So I’m happy about that.
HS: You said that Steve jokes that it’s mostly cited by people who don’t read it, but do you have a have a sense of what it does get cited for?
NE: Well, where it stands right now, in the current literature, I don’t know. I don’t even know what the current rate of citation is. But as we went through time, people would say there is this idea, and they would basically quote it because it’s something that needed to be confronted, and it got more and more positive as time went on. You know, there were all these other issues. Steve was sort of a renowned left-winger, he was. So we were accused of being Marxist, you know. Things like this.
“Punctuated equilibria” (more often these days “punctuated equilibrium”) has become sort of the go-to phrase for describing change within all kinds of systems where change is sudden rather than gradual. It permeates our culture as the alternate metaphor to the old picture of slow, steady gradual change. Mathematicians have used it, as have social scientists and historians. It is still used in newspaper articles on all sorts of topics. So “punctuated equilibria” is like “aspirin”, or “Kleenex”—brand names used for a specific creation co-opted into the lexicon as a handy descriptive term — for similar patterns of stasis in change in all manner of different systems—well beyond the realm of the evolution of species.
HS: What kind of an impact do you think this work had on your career?
NE: Actually, if you read all of Steve’s obits, that’s the only science that goes into the public obituaries of him – it’s punctuated equilibria. So, obviously, it was enormously important for his career. It was equally important for mine. I mean, the fact that I’m living in a house in a nice neighborhood right now, and getting good salary raises, it’s all because it became well-known, you know. And I did go out, and I did do a lot of speaking and so forth on most of the continents of the world, except for Antarctica. So, no question that was the centre of my career and it had tremendously positive personal effects on our well-being here. So it was my big thing. I mean, I think there was a lot of implications for it, which I find intellectually, you know, just as interesting right now, like, basically, hierarchy theory comes out of that too. Because if you have species, they are sorted, just like individuals and so forth, then you start talking about hierarchical arrangements in nature and try to put ecology together with that, and so on. I think that there was a lot of growth and a lot of further work, but I think that was the thing that started it and probably still the most important thing. And I think it’s right. It’s empirical. So I’m very proud of the fact that we restored what was obvious to palaeontologists in the mid 19th century, which is that things do not change much, if at all, in the fossil record. It’s empirical; that’s a lovely thing about it. You can’t fight with facts unless you’re into false news reports (“fake news”). In the United States, we’re dealing with all of this right-wing stuff with falsity, but in this, the truth of the matter is that things are the way we depicted them.
HS: Following the publication of this chapter, did conceptual work around this topic become an important part of your research, in addition to the empirical work you were doing?
NE: Yeah, what happened was I started getting frankly bored with doing monographs on trilobites and so forth. My last important monograph on trilobites was published in 1980.We moved to this house in 1985 and I remember walking in the woodlot back there, back behind our house and thinking, I have to have the courage to just basically focus on theoretical matters and stop doing so much empirical work. And so I did. And so it was fits and starts of doing the theoretical work, and then expanding on that, getting into ecology. And then I came up with something I called the sloshing bucket vision of evolution. I incorporated extinctions in there with, you know, radiations and orders of magnitude of those kinds of things. But I also did a lot of work on creationism in the United States. What else did I do? Oh, and also basically I wrote three or four books on mass extinctions of the geological past on what they have to tell us about the modern world and the perils that the modern biota is facing from an ecological standpoint, as much as certainly as an evolutionary standpoint. So I went off on that, but I was interested in different issues – some of them more germane to life as it exists right now politically, and some of it still biological stuff, and so on.
HS: I also noticed that you did quite a lot of work on phylogenies immediately after this.
NE: On phylogenies? On trilobites?
HS: On hominid phylogeny…
NE: On hominid phylogeny, yeah, absolutely. Oh, yeah. so I wrote a textbook with Joel Cracraft in 1980, on Phylogenetics and the Evolutionary Process and tried to get a strict grasp on the phylogenetic perspective, that was sort of slow to grow at least over in the United States. I think our book was the first one to come out and actually examine those ideas and promote them as the way to figure out evolutionary histories. And then the idea would be – what do you do with the evolutionary histories, once you got them? Because most systematists get it, they get a bunch of species or a clade or whatever, figure it out phylogenetically to their satisfaction, and then they just jump over to another group. But the thing is, what can you do with these patterns to understand how the evolutionary process works, and what’s the interaction with ecological themes and so on?
HS: Today, it’s 44 years since you wrote this chapter. How different is your thinking about this topic today?
NE: I’m a typical old man. I mean, I just get more intransigent about my views as I get older. I think they are great. I think I have more confidence in the empirical side of it than I did 40 years ago, I was worried that I would be taken as sort of a crackpot. and somebody who was inventing something, just to gain attention or something. I wasn’t, and I was confident in myself that I wasn’t that way. But on the other hand, I was less confident in general. And I was worried because I only had the example of the one trilobites species lineage. I was helped by Carl Brett, who was a biostratiographer and palaeontologist, who in the late 80s said to me, it’s not just your lineage that’s showing these patterns in this segment of time in the Devonian. He said, it’s everything in the fauna, 200 species or something, molluscs and everything, they’re all showing the same pattern, more or less simultaneously. So now we’re into this business of the turnovers and so forth. Basically locking in and having the physical environment basically driving what’s going on.
HS: After you proposed this theory, has the way people look at fossil evidence changed? And now, is there a lot more evidence in support of your theory?
NE: Yeah, that is absolutely true. It’s funny. There’s a young woman who replaced me when I retired six years ago, and we have seldom conversed, but she just wrote me an email yesterday. She has written a paper with her former mentor who’s, I think, at the University of Chicago, looking at the whole business of stasis. And they said that, yeah, it’s a very common phenomenon. It’s not absolutely, you know, 100% of all cases, but stasis is a real, common phenomenon in the history of life.
HS: What is this person’s name?
NE: Melanie Hopkins. I was surprised and pleased, not only be replaced by another trilobite worker, which I didn’t even think would happen, but that it’s a woman is great. So I think that’s all good stuff.
HS: You are saying that there is a lot of empirical evidence in support now. Has the theory also gained acceptance among palaeontologists over time?
NE: Oh yeah, absolutely. It is taught in all palaeontology courses and I think approvingly and positively.
HS: In these 44 years, have you ever read this chapter again? Have you gone back to it for anything?
NE: I read it to write Eternal Ephemera. Prior to that, I don’t believe I really read it in detail. I don’t know. I don’t think so.
HS: When look at this paper and compare it to things you write today, do you notice any striking differences in the way you write?
NE: That’s a great question. I don’t know. It’s a little confusing with the ’72 paper because Steve actually rewrote the thing to make it seem like one person had written it. And so my style is, I guess, if you compare it, I think it was a little more stilted, a little bit more formal. Steve always told me that you should write the same way, with the same style, for a popular audience, or a highly technical audience. It doesn’t matter. The only difference will be in the vocabulary. And I took that seriously. I don’t know if I ever managed to achieve it. But I think my writing did improve. My wife is a writer and an editor and she’s helped me tremendously just to edit my stuff. Make the sentences shorter, you know, stuff like that. So I do think that I’m a bit better now. And of course now I’m getting old. But I do think I can still write pretty well.
HS: Would you count this book chapter as one of your favourites, among all the papers you’ve published?
NE: Only because of the ideas that are discussed in them and that were made evident to the public at large, the world at large. That would be my favourite for what it achieved. I don’t know what my favourite papers are really.
HS: What would you say to a student who is about to read this chapter today, 44 years after it was published? Would you add any caveats to the reading? Would you guide them to other subsequent literature that it would help to read along with this chapter?
NE: Oh, that’s interesting. I try not to tell people what to think about. I would say to them, it’s not just for historical curiosity because it’s still substantially true, but there’s a lot of other treatments, there’s a lot more data. I would point to the work of Jeremy Jackson and Alan Cheetham on fossil and recent bryozoans of the Caribbean as a thorough and now-classic study of evolutionary patterns in the fossil record—leading up to the species still alive today. Jeremy has told me that, when he was at Yale as a graduate student, he thought our ’72 paper was all wrong; absolutely wrong. And that there are examples that we gave in that paper that were not convincing or were not really well analyzed; not really scientifically done. So, years later, he comes along and he looks at the bryozoans that are alive, he’s doing some molecular stuff with them, and working with Alan Chatham, a palaeontologist, going down the last 20 million years to look at these lineages of these species that are still alive today. And he says, you guys are absolutely dead right. And I said, what about the turnovers and, you know, do things happen more-or-less across lineages at about the same time? He said, absolutely. So, I always go to Jeremy’s paper. I just tell people read Jeremy, because he was a profound doubter, he did the work at the level that he thought we should have done our work at, and he found out that we were dead right. And had the honesty and courage to publish it. So that’s what I will direct people to.
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