by Pacific Discovery associate editor Gordy Slack
Geerat Vermeij is probably best known for his work chronicling the arms race among long-extinct mollusks and their predators. By examining and analyzing fossils for evidence of interspecies competition and predation, Vermeij has prompted the field of paleobiology to acknowledge the profound influences creatures have on fashioning each other’s evolutionary fates. Vermeij, a native of the Netherlands, has concentrated, especially, on ecological interactions like competition and predation, rather than on environmental factors such as climate change. Vermeij has also made major contributions to research on the movement of species between different marine environments after the removal of barriers, and he has published on such varied topics as bird evolution and leaf shape.
Vermeij, an Academy Fellow and a professor of paleobiology at the University of California at Davis, now aged 50, has been blind since the age of three when his eyes were removed to prevent a rare disease from causing neural damage. He downplays the importance of his blindness and denies that approaching mollusks and their environments through his other senses have led him to connections other scientists may have missed. But watching him turn a shell over in his hands, feeling each bump, crenelation, and texture, it seems inevitable that this different mode of experience has influenced his analysis.
Vermeij has published nearly a hundred scientific papers and four books, including Evolution and Escalation: An Ecological History of Life, A Natural History of Shells, and a recent autobiography entitled Privileged Hands: A Scientific Life. He was the editor of Evolution, the field’s foremost journal has a world-class collection of shells, and is an intrepid field naturalist and explorer of the coasts of nearly every continent. In 1992, Vermeij won a MacArthur Fellowship.
The ecology of fossil mollusks would seem an obscure area of expertise, but speaking with Vermeij, and reading his books and articles, one begins to wonder if the study of these fossils is the key, not only to understanding specific principles of competition in evolution, but also to comprehending beauty, work, courage, and economics. And one begins to wonder, too, if these things are not all fundamentally related.
On shells and the evolutionary arms race
Gordy Slack: I believe it was in New Jersey that shells really caught your attention?
Geerat Vermeij: Yes, my school teacher had brought shells back from Florida and they were so much fancier and more evenly sculptured than the temperate shells I had collected in the Netherlands and on the New Jersey shore.
GS: What was it about shells that held such a great attraction?
GV: They just have everything going for them as far as I’m concerned. As natural objects go, they are first of all easily handled. They are the right scale, the right size. They are geometrically very pleasing because they have that spiral structure and they show lots of contrasts in texture; there are all sorts of ribs and there are smooth areas, and the inside is different from the outside. They satisfy a lot of aesthetic demands. And there are just about endless variations on the shell theme. There is diversity, there is regularity, there is sculptural contrast. They evoke questions about why some are so fancy and others so plain.
GS: In your book, you ask why tropical shells are so smooth and polished and why cold water shells are chalky.
GV: That occurred to me because I saw this contrast between Florida and Dutch shells. There are several levels of explanation, all of which probably have some merit. One way of putting it is that the temperate shells are simply sloppily built. You don’t see the great regularity of growth in the temperate shells that you do in the tropics. One explanation might be that the process of laying down calcium carbonate, of which these shells are built, is less carefully controlled in the cool, temperate faunas than it is in the tropics. And one reason for that might be that the calcification that takes place, the laying down of mineral, is a good deal more expensive in temperate waters. Calcium carbonate precipitates much more readily in warm water than in cold. So the whole process of making a shell may be energetically much more expensive in cooler regions. There are also many more demands placed on tropical shells than on temperate ones — demands by predators, potential borers that live inside shells, and many other things. You are simply setting a higher standard for building shells in the tropics. Shells are very much like houses. If you live in a strong area you’ve got to build a stronger house.
GS: Among the things you are best known for is your investigation of the arms race among marine invertebrates. Would you say a few words about how your thoughts on the subject evolved?
GV: My arms-race idea evolved from the simple observation that Pacific shells appear more armored — more strongly knobbed, with a smaller opening — than tropical Atlantic shells. I thought about this difference, began to test the idea that differences in the power of shell-crushing predators was responsible, and then saw that modern organisms are better fortresses than ancient ones. In other words, some sort of escalation had occurred.
GS: You have also drawn analogies between invertebrates’ arms races and those of humans.
GV: I think they are more than analogies. They are actually the same principles. In fact I have a running battle with some people arguing that evolutionary and economic principles are in many ways identical. And the same is true of principles having to do with the arms race. The argument is that there is no organism on Earth that doesn’t have competitors and there is no human on Earth that doesn’t have competitors. Competition for mates or food is just a fact of life whenever there are resources that can be taken up by more than one entity. I’m using competition here in the very broad sense to include being eaten. Predation is one form of competition that happens to involve eating you. An awful lot of adaptations and other attributes of plants and animals and of humans and of human societies are interpretable as responses to variably competitive environments. And the arms race is one manifestation of that.
GS: If that is the case, have you learned anything about de-escalation?
GV: I don’t think there is necessarily such a thing as de-escalation, but I do think there is such a thing as cessation, where the escalation stops. Why it stops and why it starts are, I think, the two most interesting questions about it. In fact, in a very perverse sort of way evolutionists have been so anxious to demonstrate that evolution occurs that many have forgotten that often it doesn’t occur, and that the more interesting questions are why not, why it starts, and how it stops.
Many of the improvements that could make you a better competitor or make you better defended unfortunately involve a good deal of energy investment. For example, this morning I had a chat with a visitor here who works on nitrogen-fixing bacteria in legumes. They form these nodules on the roots, which is why legumes are such great plants to grow between crops. It’s a wonderful thing for these plants because it makes them very good competitors. But, it turns out that these bacteria exact a very, very high price in terms of energy and resource allocation on the part of the plant. So it’s an expensive luxury, but it does give big advantages.
Well, the same is true for such things as endothermy or warm-bloodedness in animals. It is incredibly expensive, but it also gives you huge advantages. Obviously the same is true for nuclear weapons and for very large battleships. These things are incredibly expensive, but they do provide you with at least temporary competitive advantages or prevent others from taking your territory. Even if you don’t use the weapons, there still is that deterrent effect.
GS: What happens when the economy inevitably begins to contract and you can no longer afford to maintain those defenses? Does specialization bring on extinction when the economy shrinks?
GV: Probably not directly, but specialization probably predisposes organisms to be more vulnerable to the events that cause extinction. It does look as if the biologically most sophisticated organisms are prone to extinction, either because they require a steady supply of food, or because something interfaces with reproduction. We are far from understanding just how all this works, but it is clearly an important issue.
You’ve already got the weapons, but you’re not going to develop them any further. You’re going to reach a status quo. Competition is still there, and there is lots and lots of predation in nature and in human societies. There is never going to be an end to friction. But one’s ability to respond through adaptation is very limited because there are all these conflicting demands; you improve in one direction and you have to make compromises in others. So the general result is going to be a stalemate, which will remain until there is some other kind of a breakthrough. And I think that one of the commonest breakthroughs would be a further increase in resource availability or energy availability.
GS: Does the breakthrough ever come in the form of an adaptation that allows for new forms of energy exploitation?
GV: There is a continuing debate about where those breakthroughs come from. The older school of thought argues that most of the big adaptive breakthroughs come through happy coincidences within organisms. For example, the evolution of endothermy can be considered such a breakthrough. The evolution of vascular systems in plants is another one. A very common class of these kinds of breakthroughs would be the origins of certain symbioses, like the nitrogen-fixing bacteria, or the possession of microbial fungi on roots so that plants can take up minerals more effectively. But, as I pointed out, every one of these, whether they be symbioses or just new structures or both, is energy-intensive and it may therefore be that even these innovations will not arise or will not be very successful unless there is enough energy to take advantage of.
My sense is that it is largely but not entirely the extrinsic input that matters. Now it is certainly true that if organisms are given a lot of nutrients or a lot of energy there must be ways of recycling them or taking good advantage of them, which often means in some sense a positive feedback. For example, it turns out that quite a lot of animals burrow in sand and mud, and the action of burrowing brings up nutrients or at least recycles nutrients so that they are not hidden in the sediment from the rest of the biological system. So you’re recycling them, which in effect means you’re increasing the supply of those nutrients. Well, the act of burrowing is itself an energy-intensive operation. But clearly, with an increase in nutrients, and with this recycling ability, you are greatly expanding the initial effect; it’s a positive feedback. I think this is very, very common. So, yes there may be a fundamentally extrinsic trigger, but the organisms can take advantage of it.
On punctuated equilibrium
GS: It sounds like you fall pretty squarely into the punctuated equilibrium camp on questions of rates and constancy of evolutionary change.
GV: Only up to a point. I think that the only significant contribution punctuated equilibria made is to emphasize something that evolutionists have actually known all the time but have in fact ignored, and that is that evolution isn’t constant and that there really are long periods when evolution is essentially not taking place. There are a lot of other things that come along with the punctuated equilibria theory that I don’t buy. The most important one of which is that evolution occurs only at times when there is lineage splitting going on. I just don’t see any evidence for that at all. There is no reason why evolution has to always involve lineage splitting. You can have a single lineage in which evolution occasionally stops and starts. It’s as simple as that.
GS: Many molecular biologists seem to think the punctuated equilibrium issue is closed and that the court favors constancy.
GV: Two comments about that. First of all it is impossible for a molecular biologist to know the dynamics of the evolution of molecules. We don’t have a fossil record of molecules so we do not know. We cannot know. I think it is wishful thinking to say that evolution is always going on. In fact, we do not really know how to measure rates of molecular evolution. There are all kinds of possible ways of doing it, but they’re all based ultimately on calibrations from the fossil record, some of which are highly suspect.
Now it is also true that there are molecular changes that take place in evolution that are truly neutral in the sense that they seem to be unobserved by natural selection. I am prepared to believe that those things do go on, probably more or less constantly, because they simply are not adaptive evolution. But of course, the part of evolution that I look at is to a very large extent adaptive, and, moreover, I would argue very strongly, in contradiction to [paleontologist and punctuated equilibria proponent] Steve Gould, that adaptation is the dominant theme in evolution. Getting back to that theme of competition being ever-present, what else would you expect?
On describing new mollusks
GS: What percentage of the world’s mollusks have been described?
GV: There is a paper that just came out by my friend and collaborator, Philip Boucher in Paris, who has actually followed the numbers of new species that have been described in the last 40 years and he is literally tallying them up, and he finds that the number described per year is roughly constant. I think it is on the order of four or five hundred a year, which is a fairly large number. And the numbers seem not to be declining. One could say, ‘Well, maybe a lot of those will turn out to be synonyms,’ but he’s also studied how many of them have turned out to be synonyms and that ratio is about constant also. So you can reduce the actual number of taxa by some proportion but it will still be constant over the years. What is interesting is that the number of marine species being described is actually increasing every year and the number of land and freshwater mollusks is decreasing. In the case of land mollusks, that reflects only the lack of expertise and it probably means that we’re falling behind there.
GS: You mean we’re just not educating enough taxonomists?
GV: Right. There are only about ten people in the world who describe land snails, none of whom is living in the United States. To get back to your question, though, I think that there is a long way to go in describing even living mollusks, to say nothing of fossil ones. Let me give you one other anecdote which I find very instructive. In 1982 I had a graduate student named Brad Kent at the University of Maryland. In that year he published a paper in which he described a new species, a thing called Beauticom something or other. It’s a whelk, about six or seven inches long. It is the largest living mollusk on the coast of Maryland and Delaware and it’s a new species. You would have thought the fauna of Delaware and Maryland would be pretty bloody well known. But obviously not well enough. And even in Britain and in Holland, whose faunas are as well known as any in the world today, new mollusk species are described every couple of years.
GS: Is the degradation of freshwater habitat causing the slowdown in discovery in freshwater mollusks?
GV: That’s part of it, but it is much worse for the land snails. I’m sure we’re missing a huge number of land snails for that reason. My sense is that freshwater faunas on the whole are better known than land faunas are. I may be wrong, but just judging from the literature that I casually read I’d have to say that the number of freshwater species is pretty well known.
GS: Why are so few students studying such a fertile field?
GV: For the very simple reason that descriptive biology is frowned upon by most academic departments. Description for its own sake is just not seen as a viable scientific enterprise. If you’re a student who wants to get a job, that kind of descriptive work must be done in the context of larger questions that you’re asking and not be an end in itself.
Now there are plenty of people who obviously spend their lives, and once in a while their careers, describing species. I like that, and I use their work all the time myself. But almost always it’s just not a viable way to make a living. In the case of mollusks, we’re fortunate, because there are legions of extremely capable amateurs who are doing a lot of the description. I worked with one of them, a man named Ronald Houart in Belgium, who is one of the world experts on a certain family of snails. He has described the preponderance of species in that family.
GS: Are a good percentage of those four hundred new species a year described by amateurs?
GV: Yes, a fair number. I’d bet it’s a good half.
Big biology questions
GS: What do you see as the major questions of your field of biology now?
GV: My answer will be tinged with my own biases. One very valuable way of thinking about biology is to ask why things don’t exist. Why it is that certain plausible modes of life or kinds of organisms have not evolved? Or if they have evolved, why didn’t they evolve earlier, or why are they no longer there? There are, for example, different types of morphology, and different modes of life that occurred in the past that don’t occur today, and vice versa, and it’s worth asking why that is. It would give us some insight into the limitations or constraints operating that we don’t now imagine.
GS: Do you think there may be general principles of constraint?
GV: There may be. For instance, there are almost no hermit-crab-like creatures that live in empty shells in freshwater. Now that’s a curious fact, something to store away. There are almost no predators in freshwater that use distance chemoreception. There are very few mobile animals that have the ability to manufacture their own food. All of these things are plausible, so why aren’t they more common?
Mollusks in a mean world
GS: You’ve shown that fossil mollusks are a lot different than modern ones, that armor which would have worked pretty well some millions of years ago just wouldn’t hold up today. Is the world becoming a meaner, more competitive place for organisms in general?
GV: You bet! I would be willing to bet that the world on average, within certain environments, has become a more rigorous place to live. Much as human society has, in some respects, become a more demanding place to live.
GS: Are there refuges?
GV: Lots of them. Living in the soil as compared to living on top. Organisms active at night don’t seem to have quite as much to worry about as organisms about during the day. There are many examples, and they can be boiled down to ‘Why is it that we don’t find a, b, or c in these environments?’ In fact that’s how my explorations started because I was puzzled by the differences between the Caribbean and the Indo-Pacific. Why is it that we find all these heavily armored things in the Pacific and to a much lesser extent in the Caribbean?
I think the answer is a combination of less extinction and more opportunity for evolution in the Pacific as compared to the Atlantic. The greater diversity of the Pacific may itself also play a role here. Diversity and history are not, of course, independent, so further work will have to approach the question from various points of view.
GS: Are mollusks particularly vulnerable to environmental degradation? When this page of natural history is looked at a thousand years from now, will we see a massive extinction event among mollusks in the fossil record?
GV: Well, we’re seeing one in land snails. We’re not yet seeing it in marine mollusks. We have seen it in freshwater snails.
GS: Do these human-caused declines suggest that more attention should be given to conservation biology, to the protection of biological diversity? Is this a concern of yours?
GV: Absolutely. I value diversity more than you can imagine. I value it for its own sake, for the sheer beauty and unpredictability and surprise of it all. I want to preserve diversity, which means that I want to preserve the natural habitats — the context — in which organisms evolved and continue to thrive.
There is a lot of justifiable concern about biodiversity today, but I am also persuaded that most scientists who are involved in biodiversity do not know exactly what it is that they would like to know. They cannot somehow translate their concern into a sustainable scientific project. And I think that asking the right questions is an absolutely key element. Of course, that is often something you learn after the fact. But still, it is important to think about.
One of the hopes in biodiversity is that “diversity” actually means something. We all intuitively think that it does, but few of us have dared to ask. It would be nice if diversity has a significance to ecosystems beyond aesthetics. It is probable that, above some minimal diversity, ecosystems become more stable in terms of how geochemical cycles are regulated by organisms; but are other principles of ecosystem function diversity-dependent? This is a fundamental question. Even if the answer proves to be no, the aesthetic considerations should be more than sufficient to compel us humans to protect what diversity is left.
In the same way, there are surprisingly few good data on how much extinction there has been. We could do a whole lot better. Especially by going into museum collections and looking at specimens that haven’t been collected for years and trying to track all of these things down and asking why we are not finding them. Is it because we haven’t looked or because they are really gone? We could, I think, do a vastly better job than we have at estimating extinction.
The more we learn about patterns of extinction relative to where organisms are living geographically and ecologically, the better position we will be in to predict extinction and to prevent it.
Also in terms of invading organisms, there is a strongly held view by many biologists — which I think is largely emotional, though, of course, in many cases it may be true — that invasion is a bad thing. Well, I think we need as scientists to be more dispassionate than that. We need to see in how many cases is it bad, under what conditions is it bad, and what we can learn about invasions that matter and invasions that don’t. I think those questions are rarely asked because we are so used to thinking that invasion is bad that we don’t think more broadly about it.
GS: In the San Francisco Bay Estuary invasions have actually increased biological diversity.
GV: There’s a good case in point where invasion absolutely doesn’t make a goddamn bit of difference. The San Francisco Bay Estuary is about twelve thousand years old and its fauna hasn’t been together in its “native” form for more than a couple of thousand years. Yes, there have been hundreds of introduced species. But so what? There was no community there to start with. It’s a very good case in point.
GS: How are those who don’t want San Francisco Bay invasions different from you not wanting the Panama Canal to go to sea level and letting everything move from one ocean to the other?
GV: I wouldn’t like to see it done, partly for emotional reasons, to be sure. I have made predictions about what would happen and I think some of the things would not be good, but I think a lot of it probably wouldn’t matter.
Invasions have always gone on. We now think of the guanaco, and alpaca, and vicuna as native to South America. But we have to remember that that group of camelids arrived a couple of million years ago, or maybe only one million. I guess they diversified there, but hey, they’re immigrants. Same thing is true for a whole lot of things in the North Atlantic that came from the North Pacific about three or four million years ago, hundreds and hundreds of species. They came in as invaders.
GS: But the time scale there is so wildly different. Isn’t a million years a lot different than a decade when you’re talking about the effects of hundreds of introductions?
GV: Well, we don’t know what the dynamics of invasion were at all. All I’m saying is that if we’re going to study invasion or extinction or anything else having to do with biodiversity we should, as scientists, if not as citizens, suspend our emotions a little bit more and ask the important and perhaps uncomfortable questions.
I love diversity, and I am a conservationist as much as anyone can be. And I put my money where my mouth is. I want to see human population tithed, diminished by nine-tenths if not more. I want to see all these trends reversed. But I’m also a scientist and I think we need to ask the difficult questions.
- Read about evolutionary arms races and coevolution in Evolution 101.
- Find out what punctuated equilibrium is and how it works.