On July 5, renowned evolutionary biologist Ernst Mayr celebrated his 100th birthday. He also recently finished writing his 25th book, What Makes Biology Unique?: Considerations on the Autonomy of a Scientific Discipline [Cambridge University Press, in press]. A symposium in Mayr's honor was held at Harvard University on May 10. Scientific American editor and columnist Steve Mirsky attended the symposium and wrote about it for the upcoming August issue. On May 15, Mirsky, Brazilian journalist Claudio Angelo and Angelo's colleague Marcelo Leite visited Mayr at his apartment in Bedford, Mass. Edited excerpts from their conversation appear below.

For a PDF of the entire interview, click here.

Claudio Angelo: What is the book about?

Ernst Mayr: What the book is about. (Laughs.) Primarily to show, and you will think that this doesn't need showing, but lots of people would disagree with you. To show that biology is an autonomous science and should not be mixed up with physics. That's my message. And I show it in about 12 chapters. And, as another fact, when people ask me what is really your field, and 50 years or 60 years ago, without hesitation I would have said I'm an ornithologist. Forty years ago I would have said, I'm an evolutionist. And a little later I would still say I'm an evolutionist, but I would also say I'm an historian of biology. And the last 20 years, I love to answer, I'm a philosopher of biology. And, as a matter of fact, and that is perhaps something I can brag about, I have gotten honorary degrees for my work in ornithology from two universities, in evolution, in systematics, in history of biology and in philosophy of biology. Two honorary degrees from philosophy departments.

Steve Mirsky: And the philosophical basis for physics versus biology is what you examine in the book?

EM: I show first in the first chapter and in some chapters that follow later on, I show that biology is as serious, honest, legitimate a science as the physical sciences. All the occult stuff that used to be mixed in with philosophy of biology, like vitalism and teleology-Kant after all, when he wanted to describe biology, he put it all on teleology, just to give an example-all this sort of funny business I show is out. Biology has exactly the same hard-nosed basis as the physical sciences, consisting of the natural laws. The natural laws apply to biology just as much as they do to the physical sciences. But the people who compare the two, or who, like some philosophers, put in biology with physical sciences, they leave out a lot of things. And the minute you include those, you can see clearly that biology is not the same sort of thing as the physical sciences. And I cannot give a long lecture now on that subject, that's what the book is for.

I'll give you an example. In principle, biology differs from the physical sciences in that in the physical sciences, all theories, I don't know exceptions so I think it's probably a safe statement, all theories are based somehow or other on natural laws. In biology, as several other people have shown, and I totally agree with them, there are no natural laws in biology corresponding to the natural laws of the physical sciences.

Now then you can say, how can you have theories in biology if you don't have laws on which to base them? Well, in biology your theories are based on something else. They're based on concepts. Like the concept of natural selection forms the basis of, practically the most important basis of, evolutionary biology. You go to ecology and you get concepts like competition or resources, ecology is just full of concepts. And those concepts are the basis of all the theories in ecology. Not the physical laws, they're not the basis. They are of course ultimately the basis, but not directly, of ecology. And so on and so forth. And so that's what I do in this book. I show that the theoretical basis, you might call it, or I prefer to call it the philosophy of biology, has a totally different basis than the theories of physics.

If I say so myself, I think this is going to be an important book. The philosophers of course will ignore it, it's bothersome, it doesn't fit into their thinking. And so the best way is to just forget it, put it under the rug. But those who take it seriously will say, well, gee, that's not something I know how to deal with. But this fellow Mayr seems to have something here, nobody else has made that so clear, nobody else has shown that, really, biology, even though it has all the other legitimate properties of a science, still is not a science like the physical sciences. And somehow or other, the somewhat more enlightened philosophers will say we really ought to deal with that. But so far they haven't.

SM: So would you say that before Darwin-you have a period after Newton but before Darwin-in that period, physics is a science that's different from biology?

EM: Absolutely. You have a marvelous historical document that illuminates that. Kant, after he had shown in the Critique of Pure Reason how in the physical sciences everything is based on natural laws, that was supposedly Kant's great contribution, and then he went on, in 1790, to show that biology is no exception, that it's also based all on natural laws. He describes [this] somewhere in the early chapters of the Critique of Judgment. And he tried to base the generalizations, let's call them laws, of biology, on natural laws, and it just didn't work. It was a complete disaster. And so finally, he said, you have to base them on something else. Well, what? And he said teleology. Aristotle's fourth cause, finality. Everybody has been trying to show how Kant had the right instinct to get away from the natural laws for biology and adopt instead teleology. Well, one of the chapters in this forthcoming book of mine is devoted to showing that this doesn't work. There is no such obscure force in nature like teleology, like Aristotle's fourth cause.

CA: So, would you say that the whole quest of molecular biology to try to ascribe everything to chemical bonds and physical laws is the same mistake that Kant made?

EM: Well, I now will jump ahead to what probably would have come out gradually. When did biology originate? Well, not in the 17th or 18th century. You had fields of biological activity, like anatomy and taxonomy and other things like that. But you didn't have a field like biology. Now the word biology, curiously enough, was proposed three times around the year 1800 by three different authors. My claim, which I make in earlier books, is that biology as a field, something that you can recognize as something different from the physical sciences, that you can really designate with a single word, developed and originated and became what it is, biology, in a relatively short number of years. Around 40 years, between 1828, when Karl Ernst von Baer organized developmental biology, embryology, and then came very soon after that, the two authors of cytology, Schwann and Schleiden, who caused a tremendous uproar at the time when they published their work in the 1830s, because it showed that animals and plants are composed of the same elements, cells. So that was a major contribution toward the science of biology. And then comes a big period of physiology, Claude Bernard in France and in Germany they had two or three authors that were the great physiologists, Johannes Miller was one. So that's the third field.

And then genetics, of course. Genetics was the last one. The next one in time that developed, of course, was Darwin's and Wallace's evolutionary biology. And finally, in 1865-66, genetics. Now this series of six sciences beginning with embryology and ending with genetics was the founding of biology. And you can really argue about what is biology only after you have nailed that down, because this compound of things, including genetics, evolution and so forth, is biology.

Now, you asked what about molecular biology. Well, let me now again sort of go a step or two back. There was a very crucial period in the early part of the last century during which the so-called evolutionary synthesis took place. And up to that time, meaning the period between 1859 and the evolutionary synthesis, which was in the 1940s, there was a great turmoil in evolutionary biology. There were at least four if not five major basic theories of evolution, for instance. But anyhow, the evolutionary synthesis, initiated by Dobzhansky and then joined by people like myself and Julian Huxley and Simpson and Stebbins and so forth, the evolutionary synthesis sort of put a stop to the major theorizing, particularly in the evolutionary field. And what is very interesting, then you have Avery showing that nucleic acids rather than proteins are the genetic, evolutionary material. And then came Watson-Crick. And then came all the developments in molecular biology and finally the developments in genomics. And each time one of these major upheavals occurred, we expected the theory of the evolutionary synthesis to have to be rewritten. But the fact is, and I don't know whether any molecular biologist has complained about it, or expressed regrets, that none of these major upheavals in the factual structure of this new biology from Avery to genomics, none of these changes really affected what is usually referred to as the Darwinian paradigm, the set of theories that make up modern Darwinism, from let's say the 1950s, let's say from Watson-Crick to today. And new books come out all the time in which the author tries to prove that Darwinism is invalid. Well, I think even if you're a neutral outsider, you will admit that none of these books has been a success. And in the end, it has always been showed that Darwinism was and is correct.

But this is now finally the answer to your question. The funny part is that molecular biology has a remarkably small impact on the theory structure of biology. At least that's the way it looks to me. Of course, they can point out that the genetic code has shown that life as it now exists on the earth could have originated only a single time, otherwise it wouldn't be the same code that it is. And of course there are several other things that molecular biologists have contributed. But none of them really touched the theory structure of the Darwinian paradigm, in my opinion.

SM: If anything, hasn't it been the opposite, that the synthesis informs the molecular biology work.

EM: Right, yes. That's molecular biology's theory structure.

Marcelo Leite: But on the other hand, molecular biology is seen by molecular biologists and also by the public as the kind of defining moment of biology in the 20th century. They kind of reconstruct the whole history of biology as if pointing to molecular biology and the human genome project as the climax of this. So this is a wrong way of seeing 20th century biology?

EM: There is no doubt. If you go further back, the molecular biologists take everything else that happened for granted. On the other hand, if you're a cytologist, you could say that the Schwann-Schleiden demonstration that all organisms consist of cells, and that the cells have a nucleus and all this sort of thing, that all is as much a foundation of biology as, let us say, that nucleic acids consist of base pairs. I don't see anything more, in fact, I would say that from the point of view of philosophy, these findings, these descriptive findings of molecular biology, are no more important than these, let's say, achievements from the origins of biology in the period from 1828 to 1866. Those findings made in that period are at least as important as anything in molecular biology.

They [molecular biology's findings] are very important, I'm not running it down. But I'll give you another historical example that's very interesting. Let's say, in the 1950s, right after Watson and Crick, a lot of chemists, biochemists and physicists, went away from their physical sciences into biology. And they were very often making the appropriate amount of noise, they were very successful in being considered great innovators in science. And very often they became the chairmen of biology departments, and there are at least three cases known and probably more if you would look at enough colleges and universities, where a biochemist or a straight chemist usually, became the head of a biology department. And he just got rid of every organismic biologist. He said we don't need them, they're not biology, biology is molecules.

ML: Well, James Watson is still writing this.

EM: No, James Watson is broader. If you carefully read what he says, yes he emphasizes the importance of his and his school's things, but Watson has enough of an organismic biology background. Now I can tell you a true anecdote about that. Did you know that Jim Watson was an ardent birdwatcher? When he was, I assume it was the senior class of high school, his mother came with Jim from Chicago, and his mother asked me what college Jim Watson should go to to get his PhD in ornithology. Listen to that carefully, I can swear to it, this is the honest truth. I've reminded Jim of this and he's tried to be quite forgetful about it. So I said to Jim, or rather to his mother, he doesn't want to go to the best ornithology college. What he needs is to get a good education in biology. Let him go to the best school in biology. Because this special knowledge that he needs as an ornithologist he can always acquire eventually. But what he needs in order to be successful in any special branch of biology is a sound foundation in biology. And so they took my word and probably other people told them the same thing. And he didn't go to any place for ornithology, but he went to Chicago and various other places and got a very good thorough training in biology. So as a joke, and please remember this is a joke, I sometimes say, well, how did Watson ever get a Nobel Prize? Well, I'm the one who's responsible for that!

SM: If you were about to start your graduate school career today, what would you study?

EM: Well, you see, I have shifted so much in the course of my life that I really don't know, and of course part of my choices were a result of what preceded. Now, in a way I'm sometimes surprised at how advanced I was in my 1942 book Systematics and the Origin of Species. That was quite a bit ahead of its time. I had no teacher who was that much ahead. How I could see things in such a modern way I still don't understand. But I did.

SM: What do you think the major questions, or even a single question, for a young researcher today is. Where would you point that person?

EM: Well, you know, the genotype. I'll mention something that nobody ever mentions. Let's say you have now a genotype that makes a certain protein. And that protein, and you can see this in every issue of Science practically, that protein is a very complex structure, incredibly complex. Now how that step from a group of amino acids to that polypeptide [happens] is an enormous jump. I think right now everybody leaves it alone because nobody yet has figured out just exactly how to attack this problem.

ML: So you are still getting up at 6:15 every day to write letters?

EM: No sir. I'm rather dismayed how many days I have to work on my willpower very strongly in order to get out of bed before 8 o'clock.

ML: But you still write letters in the morning.

EM: I write letters, I write manuscripts, in addition to the book that is in press I have two manuscripts that are going to be published some time this or next year, and I have a whole list of manuscripts that I would like to write. And people say, Why do you punish yourself like that??And I say, Punish, hell! I enjoy it!