“Well, I think I would encourage him or her to read the more recent papers of my graduate student, as a way to bridge the gap between the 1984 paper and now. I was pleasantly surprised that what Gerald [Carter] found, with a lot more data, was not all that different from what I had said in the 1984 paper.”

“Well, I think the paper can be approached on its own largely because it’s so visceral. I guess what was really lacking from the paper back then was any information on the underlying mutational process. And so, I would want to draw their attention to some of the papers that have described the underlying genetics (There are, for example, a series of papers in Genetics with me as last author) so that there’s no doubt that this really is all driven by spontaneous mutation selection. In terms of caveats, it’s not a caveat really, but rather how science works. I rather like the fact that we were able to show that we had it wrong with regard to the 'fuzzy spreader'. As you investigate things, you may find what you once thought to be true, no longer the case. Some piece of information has caused you to revise a particular position. And I like very much, and get students to read, the paper by Gayle Ferguson and Frederic Bertels in Genetics in 2013, which is titled something like “A revision of the Pseudomonas radiation”. This is a good example of how science works. Again, this is not really a caveat, but something that I would emphasize. My advice to someone reading for the first time, might be to sit back and see how extraordinarily simple this piece of work is, and yet how challenging it might have been to unravel. Sometimes, just looking at the world differently can take us to unexpected places.”

“Well, now, of course, I think a lot of that has been solved, more so than it was then, but I don’t really disagree with those conclusions. In looking at it again now, I’m actually surprised at how much I got right, to be honest. Together with other people, I’ve elaborated a lot of things. And some things have changed as well. For example, we now know that some of the escalation occurred earlier in the Paleozoic. We also know that the Mesozoic revolution itself is, probably, a two or more phase process, which we didn’t realize at the time. These are important nuances, but the basic conclusions, I think, are right.”

“What often comes to mind in this context is the impact this paper had, and it continues to be highly cited, despite some methodological flaws. It was published at about the same time as Hurlbert’s influential paper on pseudoreplication. Our work was a classic case of pseudoreplication – a pond divided in half with one treatment assigned to one half and another treatment to the other half. We think it is interesting for a student to consider what criteria they would use in taking lessons from studies that are flawed in some respect. How does one evaluate what is lasting and useful despite methodological flaws and why? We subsequently replicated such experiments across ponds, but it is daunting to imagine replicating this experiment given the amount of work that went into one divided pond. Scientific knowledge increases by incremental steps. This experiment was a first step in revealing the profound impact of non-lethal effects of predators on their prey. Thus, it was valuable despite its methodological flaws.”

“When I finished my PhD I had just spent 26 months of a five year period living largely by myself in the tropics, with not a lot of intellectual interaction. At that point, I decided that this was not a good strategy in the long-term. I didn’t want to be like a primatologist spending years on end studying one species. [...] At that time, I think I also felt that I had got, kind of, the most interesting story out of the vampire bat, given the technology at that time, and doing anything more would have been very hard. The next step required a captive colony, for which I didn’t have the resources then. [...] Then Jerry [Carter] approached me [...] about coming to do essentially a follow up of my PhD work. He really had a very clear idea of what he wanted to do. He had read my papers very thoroughly, knew exactly what I’d found and was aware of the debate over the merits. He loved the story and really wanted to confirm the story.”

“When one is reading a paper, one should really look at from a historical perspective. This particular paper was one of the first papers in a field that is now very well developed but did not exist at that time. Without that knowledge, one would probably get a very different impression of the paper. The caveats to the paper would be to do with issues related to doing laboratory assays on wild-caught birds and bringing them back into the wild to study their fitness, which we have been addressing over the next few years after the paper was published. We, and others, have published various papers on how these concerns may be alleviated or addressed. We also, now, have changed, substantially, how we do the statistical analysis of the papers, both in terms of whether we describe patterns versus a priori work out what sort of effects are muddled in our analysis, and in switching from frequentist approaches, where we were focusing, maybe obsessively, on p-values, to Bayesian approaches, where we are much more interested in estimating effect sizes. So, when I look back on this paper, I really see that the field has moved, mostly, forwards. That, I think, is a positive way to conclude a self-criticism of the papers that one has published.”

“Whole-ecosystem experiments were unfamiliar back in those days. Ecologists wanted experiments to be done in tiny containers with lots of replicates, but it is impossible to study trophic cascades realistically in tiny jars. When I look at the paper today, I think the amount of statistical detail we included is rather ridiculous. But we had to include it to placate the referees.”

“Yes and no. It has actually been a fascinating example of how science works. Yes, because many of the observations have been confirmed in later studies on different populations of the same (and other) species. For example, there is little doubt now that females play an active role in seeking extra-pair copulations, and it has also been confirmed in blue tits that extra-pair males are larger. However, the conclusion that females seek extra-pair copulations to obtain good genes benefits was probably premature. Initially, we found additional support for this hypothesis. We could show that extra-pair offspring were in better condition and were more likely to survive than their within-pair half-sibs. Most of my colleagues and I were convinced that this was good evidence for genetic effects, because we thought that within- and extra-pair offspring only differed in paternal genes. These offspring indeed share the same environment because they grow up in the same nest and they have the same maternal genes. At the time, there was some discussion about whether males would treat within- and extra-pair offspring differently, but we thought that this was highly unlikely. Another possibility was that extra-pair offspring would do better because the eggs from which they came hatched a bit earlier, and thus the extra-pair young would have a head start in life. I had actually rejected this idea after looking into it during my post-doc at Queen’s University where I worked on extra-pair paternity in tree swallows and eastern bluebirds. However, when it comes to blue tits, who lay large clutches of up to 15 eggs, it turned out I was wrong. Colleagues from the University in Groningen showed in 2009 in a paper published in Current Biology that extra-pair young are much more likely to be among the first laid eggs and because first laid eggs hatch first and generally do better, this alone might explain the extra-pair young’s superior performance. It’s really great work and I am still shaking my head that we did not do it ourselves.”

“Yes, I would delete the parenthesis saying “a group of compounds” because we now know it is cyclic AMP, one small molecule [...] the substance was identified as cyclic AMP by David Barkley and Theo Konijn in my laboratory in 1947.”

“Yes, I would say that the conclusions regarding changes in plant composition hold true, and that our confidence in those conclusions has grown.”

“Yes, the main conclusions still hold true, and that’s why it keeps being cited. And if I were to redo it today I can’t think of anything that I would change. Of course, nowadays, we can add lots of interesting genome methods.”

“You know, right now I’m working on a project where we’re trying to get rid of the four paradigms. I think they were really useful for a while. But now they are kind of getting in the way because they are highly idealized and not really likely to actually apply to more realistic situations.”