STEPHEN JAY GOULD: THE PATTERN OF LIFE'S HISTORY

Within a profession, certain issues can become very big which, if seen from the outside, might not seem so. For instance, in evolutionary theory, on the outside the only issue might be whether evolution is true or not. That's the big one! On the inside, of course, everyone knows that evolution is true; the issue is how it occurs. The main difference between Richard Dawkins and myself has to do with the agency of natural selection, and its power, and the degrees of adaptation that it produces. Within the field, these questions define the essence of Darwinism; outside the field, they might seem smallish. It is just a question of perception.

Richard wants natural selection to be effectively all- powerful, at least when you are dealing with the phenotypes — the forms of organisms. He wants the locus of that selection to be genes. I maintain that natural selection works on a hierarchy of levels simultaneously, of which genes are one and organisms are another, and that you also have higher units, such as populations and species, at which selection is very effective, and the end result is not always, by any means, adaptation — particularly when you see the process unfolding in millions of years of geological time.

No matter how effective adaptive change might be in the moment, when you start translating that and any other process into millions of years, it doesn't work out that the history of life is under adaptative control, because you have to get through these largely random and highly contingent mass-extinction events, as well as new species arising by punctuated equilibrium. Long-term success in clades is the function of speciation rate, which has very little to do with the morphologies that are built by natural selection. So Richard's and my whole views of evolutionary mechanics are very different, but to the outsider, who may only be concerned with whether evolution happens or not, we probably seem to be pretty similar, because we are both evolutionists.

I would call Richard's approach hyper-Darwinism. The brilliance of Darwin's argument, and the radical nature of it, lies in changing the focus of explanation. Before Darwin, people thought that organisms were well-designed because the highest- order force was doing it directly. There was a benevolent, creative God who made it that way. The brilliance of Darwin is that he beat the level of explanation down to organisms, saying that organisms are well-designed as a side consequence of their struggle for individual reproductive success. It is a deliciously radical argument. Instead of an all-wise, benevolent, purposeful God, what you have are organisms struggling for personal advantage — which seems to be the moral opposite, except that there is no morality in nature — and as a side consequence you get good design of organisms.

Richard has taken that posture of trying to beat the level of explanation down, and has carried it to its ultimate extreme: it's not even the organisms that are struggling, it's only the genes. The organisms are "vehicles." That's his pejorative word; most of the profession calls them "interactors," which is less pejorative. The only active agents in Richard's worldview are genes. He's wrong. If you read the British philosopher Helena Cronin's book The Ant and the Peacock, she argues that the whole profession has been transformed by this idea. Whatever my personal point of view might be, her claim is sociologically wrong in a purely factual or Gallup Poll sense. Not many people take this view seriously. A lot of people like it as a metaphor for explanation. But I think that very few people in the profession take it seriously, because it's logically and empirically wrong, as many people, both philosophers and biologists have shown — from Elliott Sober to Richard Lewontin to Peter Godfrey Smith.

Richard is basically wrong, because organisms are doing the struggling out there. If organisms could be described as the additive accumulation of what their genes do, then you could say that organisms are representing the genes, but they're not. Organisms have hosts of emergent characteristics. In other words, genes interact in a nonlinear way. It is the interaction that defines the organism, and if those interactions, in a technical sense, are nonadditive — that is, if you can't just say that it's this percent of this gene plus that percent of that gene — then you cannot reduce the interaction to the gene. This is a technical philosophical point. As soon as you have emergent characteristics due to nonadditive interaction among lower-level entities, then you can't reduce to the lower-level entities, because the nonadditive features have emerged. These features don't exist until you get into the higher level. His argument is wrong. It's not just a question of being inadequate. It's wrong.

Admittedly — again, in a sociological sense — it's enormously appealing. When you realize what Darwin did, which was to break down the explanation from the benevolent God to the struggling organism, the notion that you might break the explanation down further, to the struggling gene, has a certain reductionist appeal. But if you surveyed the profession, although not all of them would necessarily agree with me about hierarchical selection, most would say that Darwin was right and selection is primarily on organisms, which has always been the traditional view.

Gene selectionism was never a paradigm that attracted large numbers. What did happen was that the generation before Dawkins, culminating in 1959, had a form of very strict Darwinian adaptationism, a more classic, organism-centered Darwinian approach that wasn't by any means totally wrong but was much too restrictive. It did become a ruling view within evolutionary theory, and to some extent we're still fighting it, in talking about large-scale, macroevolutionary changes as not being fully extrapolatable out of the adaptive struggles of organisms and populations.

I might be on the periphery of orthodoxy, but I certainly think natural selection is an enormously powerful force. Darwin's canonical form of it — that is, selection operating on individual bodies via the struggle for reproductive success — just isn't capable, by extrapolation, of explaining all major patterning forces in the history of life. Whereas it's vital for strict Darwinism that you do accept such a view. You'll always have a little bit here and there for other things, to be sure, but unless you can argue that Darwinian selection on bodies is, by extrapolation, the cause of evolutionary trends and of the major patterns of waxing and waning of groups through time, then you don't have a fully Darwinian explanation for life's history.

I see Dawkins in a dual sense. On the one hand, he's the best living explainer of the essence of what Darwinism is all about. That part's very good. He's a kind of old-fashioned, nineteenth century, almost atheistic scientific rationalist. The other side is the strict Darwinian zealot, who's convinced that everything out there is adaptive and is all a function of genes struggling. That's just plain wrong, for a whole variety of complex reasons. There's gene-level selection, but there's also organism-level and species-level. Those are his two sides: the professional true believer, on the one hand, and the excellent explainer of a worldview, on the other.

I'd question Richard on the issue of gene-level selection and why he thinks that the issue of organized adaptive complexity is the only thing that matters. I'm actually fairly Darwinian when it comes to the issue of so-called organized adaptive complexity, but there's so much more to the world out there. Why does he think that adaptation in that sense is responsible for interpreting everything in the history of life? Why does he insist on trying to render large-scale paleontological patterns as though they were just grandiose Darwinian competitions? They aren't. He has this blinkered view in which the classic Darwinian question of adaptation is somehow becoming coextensive with all of evolutionary theory.

Richard and I are the two people who write about evolution best. He writes about microevolutionary theory, in a way I disagree with. I focus on the pattern of life's history and its relationship to evolutionary theory. I treat the fossil record and write about macroevolutionary theory, which he doesn't like. He writes on the nature of adaptation and on evolutionary theory in its traditional small-scale immediacy, and I write about the large-scale history of life.

Whether or not Darwin would be a Darwinist today, in the way the word is used, is so hard to say, because you have to make inferences about his mental flexibility. Given the set of ideas that he himself promulgated, I think he would, because his tendency in argument was always to try and stretch natural selection on bodies to cover cases. He was willing to allow a few very circumscribed exceptions, like his invocation of group selection for the evolution of human moral behavior — an important exception, to be sure, because we care about human moral behavior. But he circumscribed it in such a way that it could apply to no other species, because he invoked a group-selection mechanism that could work only in highly cognitive species that are sensitive to the "praise and blame of their fellows" — those are his words — and we're the only such species. So therefore he set up the exception in such a way as to marginalize it; it's an important one, because it's about us and we care about us, but it's not important in the full realm of nature.

On the other hand, if you want to speculate psychologically, Darwin was an enormously flexible, brilliant, and radical thinker, so I suspect that when he learned about asteroidal impact and mass extinction and maybe even punctuated equilibrium, he would be open. I doubt that he expected that a hundred years after his death things would be exactly as he had left them.