ERNST MAYR: WHAT EVOLUTION IS
From:
www.edge.org
31st October 2001
Introduction by Jared Diamond
When the
first bird survey of the Cyclops Mountains was carried out. I found it hard
to imagine how anyone could have survived the difficulties of that first
survey of 1928, considering the already-severe difficulties of my second
survey in 1990.
That 1928 survey
was carried out by the then-23-year-old Ernst Mayr, who had just pulled off
the remarkable achievement of completing his Ph.D. thesis in zoology while
simultaneously completing his pre-clinical studies at medical school. Like
Darwin, Ernst had been passionately devoted to outdoor natural history as a
boy, and he had thereby come to the attention of Erwin Stresemann, a famous
ornithologist at Berlin's Zoological Museum. In 1928 Stresemann, together
with ornithologists at the American Museum of Natural History in New York
and at Lord Rothschild's Museum near London, came up with a bold scheme to
"clean up" the outstanding remaining ornithological mysteries of New Guinea,
by tracking down all of the perplexing birds of paradise known only from
specimens collected by natives and not yet traced to their home grounds by
European collectors. Ernst, who had never been outside Europe, was the
person selected for this daunting research program.
Ernst's
"clean-up" consisted of thorough bird surveys of New Guinea's five most
important north coastal mountains, a task whose difficulties are impossible
to conceive today in these days when bird explorers and their field
assistants are at least not at acute risk of being ambushed by the natives.
Ernst managed to befriend the local tribes, was officially but incorrectly
reported to have been killed by them, survived severe attacks of malaria and
dengue and dysentery and other tropical diseases plus a forced descent down
a waterfall and a near-drowning in an overturned canoe, succeeded in
reaching the summits of all five mountains, and amassed large collections of
birds with many new species and subspecies. Despite the thoroughness of his
collections, they proved to contain not a single one of the mysterious
"missing" birds of paradise. That astonishing negative discovery provided
Stresemann with the decisive clue to the mystery's solution: all of those
missing birds were hybrids between known species of birds of paradise, hence
their rarity.
From New Guinea,
Ernst went on to the Solomon Islands in the Southwest Pacific, where as a
member of the Whitney South Sea Expedition he participated in bird surveys
of several islands, including the notorious Malaita (even more dangerous in
those days than was New Guinea). A telegram then invited him to come in 1930
to the American Museum of Natural History in New York to identify the tens
of thousands of bird specimens collected by the Whitney Expedition on dozens
of Pacific Islands. Just as Darwin's "explorations," sitting at home, of
collections of barnacles were as important to Darwin in forming his insights
as was his visit to the Galapagos Islands, so too Ernst Mayr's
"explorations" of bird specimens in museums were as important as his
fieldwork in New Guinea and the Solomons in forming his own insights into
geographic variation and evolution. In 1953 Ernst moved from New York to
Harvard University's Museum of Comparative Zoology, where even today he
continues to work at the age of 97, still writing a new book every year or
two. For scholars studying evolution and the history and philosophy of
biology, Ernst's hundreds of technical articles and dozens of technical
books have been for a long time the standard reference works.
But in addition
to gaining insights from his own fieldwork in the Pacific and from his own
studies of museum bird specimens, Ernst has collaborated with many other
scientists to extract insights from other species, ranging from flies and
flowering plants to snails and people. One of those collaborations
transformed my own life, just as the meeting with Erwin Stresemann
transformed Ernst's life. While I was a teenaged schoolboy, my father, a
physician studying human blood groups, collaborated with Ernst in the first
study proving that human blood groups evolve subject to natural selection. I
thereby met Ernst at dinner at my parents' house, was later instructed by
him in the identification of Pacific island birds, began in 1964 the first
of 19 ornithological expeditions of my own to New Guinea and the Solomons,
and in 1971 began to collaborate with Ernst on a massive book about Solomon
and Bismarck birds that we completed only this year, after 30 years of work.
My career, like that of so many other scientists today, thus exemplifies how
Ernst Mayr has shaped the lives of 20th-century scientists: through his
ideas, his writings, his collaborations, his example, his lifelong warm
friendships, and his encouragement.
—
Jared Diamond
[Excerpted from Jared Diamond's Introduction to
What Evolution Is
by Ernst Mayr — ScienceMasters Series/Basic Books; October 2001]
ERNST MAYR is Alexander Agassiz Professor of Zoology, Emeritus, at Harvard
University. He is the recipient of numerous honorary degrees and awards,
including the National Medal of Science, the Balzan Prize, and the Japan
Prize.
Mayr is one of the 20th century's leading evolutionary biologists. His work
has contributed to the conceptual revolution that led to the synthesis of
Mendelian genetics and Darwinian evolution, and to the development of the
biological species concept. His theory of peripatric speciation has become
widely accepted as one of the standard modes of speciation, and is the basis
of the theory of punctuated equilibrium. Furthermore, his writings reflect,
not only a technical expertise in biological subjects, but also a broad and
penetrating understanding of the deeper philosophical issues involved.
Among his many books are Animal Species and Evolution; Evolution and the
Diversity of Life; Systematics and the Origin of Species; The Growth of
Biological Thought; One Long Argument; Population, Species, and Evolution;
This Is Biology; and Toward a New Philosophy of Biology.
Mayr, born Kempten, Germany in 1904, began his studies of ornithology at
the University of Berlin where, in June, 1926, at the age of 21, he received
his Ph.D. In June, 2001, to honor the 75th anniversary of this event, the
Humboldt University of Berlin awarded him a second (and honorary) Ph.D.
Ernst Mayr's Edge Bio Page
ERNST MAYR: WHAT EVOLUTION IS
EDGE: To what extent has the study of evolutionary biology been the study of
ideas about evolutionary biology? Is evolution the evolution of ideas, or is
it a fact?
ERNST MAYR: That's a very good question. Because of the historically
entrenched resistance to the thought of evolution, documented by modern-day
creationism, evolutionists have been forced into defending evolution and
trying to prove that it is a fact and not a theory. Certainly the
explanation of evolution and the search for its underlying ideas has been
somewhat neglected, and my new book, the title of which is What Evolution
Is, is precisely attempting to rectify that situation. It attempts to
explain evolution. As I say in the first section of the book, I don't need
to prove it again, evolution is so clearly a fact that you need to be
committed to something like a belief in the supernatural if you are at all
in disagreement with evolution. It is a fact and we don't need to prove it
anymore. Nonetheless we must explain why it happened and how it happens.
One of the surprising things that I discovered in my work on the philosophy
of biology is that when it comes to the physical sciences, any new theory is
based on a law, on a natural law. Yet as several leading philosophers have
stated, and I agree with them, there are no laws in biology like those of
physics. Biologists often use the word law, but for something to be a law,
it has to have no exceptions. A law must be beyond space and time, and
therefore it cannot be specific. Every general truth in biology though is
specific. Biological "laws" are restricted to certain parts of the living
world, or certain localized situations, and they are restricted in time. So
we can say that their are no laws in biology, except in functional biology
which, as I claim, is much closer to the physical sciences, than the
historical science of evolution.
EDGE: Let's call this Mayr's Law.
MAYR: Well in that case, I've produced a number of them. Anyhow the question
is, if scientific theories are based on laws and there aren't any laws in
biology, well then how can you say you have theories, and how do you know
that your theories are any good? That's a perfectly legitimate question. Of
course our theories are based on something solid, which are concepts. If you
go through the theories of evolutionary biology you find that they are all
based on concepts such as natural selection, competition, the struggle for
existence, female choice, male dominance, etc. There are hundreds of such
concepts. In fact, ecology consists almost entirely of such basic concepts.
Once again you can ask, how do you know they're true? The answer is that you
can know this only provisionally by continuous testing and you have to go
back to historical narratives and other non-physicalist methods to determine
whether your concept and the consequences that arise from it can be
confirmed.
EDGE: Is biology a narrative based of our times and how we look at the
world?
MAYR: It depends entirely on when in the given age of the intellectual world
you ask these questions. For instance when Darwin published The Origin of
Species, the leading Cambridge University geologist was Sedgwick, and
Sedgwick wrote a critique of Darwin's Origin that asked how Darwin could be
so unscientific as to use chance in some of his arguments, when everyone
knew that God controlled the world? Now who was more scientific, Darwin or
Sedgwick? This was in 1860 and now, 140 years later, we recognize how much
this critique was colored by the beliefs of that time. The choice of
historical narratives is also very time-bound. Once you recognize this, you
cease to question their usefulness. There are a number of such narratives
that are as ordinary as proverbs and yet still work.
EDGE: Darwin is bigger than ever. Why?
MAYR: One of my themes is that Darwin changed the foundations of Western
thought. He challenged certain ideas that had been accepted by everyone, and
we now agree that he was right and his contemporaries were wrong. Let me
just illuminate some of them. One such idea goes back to Plato who claimed
that there were a limited number of classes of objects and each class of
objects had a fixed definition. Any variation between entities in the same
class was only accidental and the reality was an underlying realm of
absolutes.
EDGE: How does that pertain to Darwin?
MAYR: Well Darwin showed that such essentialist typology was absolutely
wrong. Darwin, though he didn't realize it at the time, invented the concept
of biopopulation, which is the idea that the living organisms in any
assemblage are populations in which every individual is uniquely different,
which is the exact opposite of such a typological concept as racism. Darwin
applied this populational idea quite consistently in the discovery of new
adaptations though not when explaining the origin of new species.
Another idea that Darwin refuted was that of teleology, which goes back to
Aristotle. During Darwin's lifetime, the concept of teleology, or the use of
ultimate purpose as a means of explaining natural phenomena, was prevalent.
In his Critique of Pure Reason, Kant based his philosophy on Newton's laws.
When he tried the same approach in a philosophy of living nature, he was
totally unsuccessful. Newtonian laws didn't help him explain biological
phenomena. So he invoked Aristotle's final cause in his Critique of
Judgement. However, explaining evolution and biological phenomena with the
idea of teleology was a total failure.
To make a long story short, Darwin showed very clearly that you don't need
Aristotle's teleology because natural selection applied to bio-populations
of unique phenomena can explain all the puzzling phenomena for which
previously the mysterious process of teleology had been invoked.
The late philosopher, Willard Van Orman Quine, who was for many years
probably America's most distinguished philosopher — you know him, he died
last year — told me about a year before his death that as far as he was
concerned, Darwin's greatest achievement was that he showed that Aristotle's
idea of teleology, the so-called fourth cause, does not exist.
EDGE: Is this an example of Occam's Razor?
MAYR: It's that in part as well, but what's crucial is the fact that
something that can be carefully analyzed, like natural selection, can give
you answers without your having to invoke something you cannot analyze like
a teleological force.
Now a third one of Darwin's great contributions was that he replaced
theological, or supernatural, science with secular science. Laplace, of
course, had already done this some 50 years earlier when he explained the
whole world to Napoleon. After his explanation, Napoleon replied, "where is
God in your theory?" And Laplace answered, "I don't need that hypothesis."
Darwin's explanation that all things have a natural cause made the belief in
a creatively superior mind quite unnecessary. He created a secular world,
more so than anyone before him. Certainly many forces were verging in that
same direction, but Darwin's work was the crashing arrival of this idea and
from that point on, the secular viewpoint of the world became virtually
universal.
So Darwin really had an amazing impact, not just on evolutionary theory, but
on many aspects of everyday human thought. My firm belief is that each
period in world history has a particular set of ideas that are the Zeitgeist
of that period. And what causes this Zeitgeist? The answer usually is that
there are a couple of important books that have been responsible for
everybody's thinking. The number one book in this realm is, of course, the
Bible. Then for many years, the answer might have been Karl Marx's Das
Kapital. There was a short period when Freud was mentioned (though I don't
think he's mentioned anymore by anyone besides the Freudians). The next one
— and there is no doubt in my mind that Darwin's Origin of Species was the
next one — not only secularized science, gave us the story of evolution, but
also produced hosts of really basic theoretical concepts, like bio-populationism
and, as I showed, the repudiation of teleology. No one before Darwin had
introduced these ideas or had advanced them so forcefully.
EDGE: Not even the scientific community outside of evolutionary biologists?
MAYR: No. They weren't brought up with these ideas, though scientists like
T. H. Huxley probably felt, as he said, "how stupid of me not to have
thought of it."
EDGE: How do you account for the fact that in this country, despite the
effect of Darwinism on many people in the scientific community, more and
more people are god fearing and believe in the 8 days of creation?
MAYR: You know you cannot give a polite answer to that question.
EDGE: In this venue we appreciate impolite, impolitical, answers.
MAYR: They recently tested a group of schoolgirls? They asked where is
Mexico? Do you know that most of the kids had no idea where Mexico is? I'm
using this only to illustrate the fact that and pardon me for saying so
the average American is amazingly ignorant about just about everything. If
he was better informed, how could he reject evolution? If you don't accept
evolution then most of the facts of biology just don't make sense. I can't
explain how an entire nation can be so ignorant, but there it is.
EDGE: I understand that there is a facsimile of the first (1899) edition of
Darwin's Origin of the Species.
MAYR: Yes and this is an interesting story. Darwin's importance has only
been gradually acknowledged. Even 50 years ago, Darwin was just one of those
people's names you learned was kind of important. That was it. Nobody read
him. Well I published a very successful book for Harvard University Press in
1963 and this gave me the courage to go to the director of Harvard Press,
Tom Wilson, and say to him, Tom, I have a great wish, a heart's desire, and
that is to see a facsimile edition of the first edition of the Origin of
Species. We have facsimile editions of all the great classics, but we
haven't got one for Darwin. So he said all right, all right, we'll do it for
you, even though we'll probably lose money since who's going to buy it? In
1964 they published this facsimile edition. That was almost 40 years ago.
and at that time, the first few years I guess they sold about a couple
hundred a year but much to everybody's surprise, sales did not drop off
after all the libraries had their facsimile edition, but rather they picked
up. After a while, they sold over a thousand a year, and then about 67
years ago I was informed by Harvard Press that for that particular year they
had for the first time sold 2,500 copies. The last two years I have a report
that they sold 3,000 copies a year! Now this shows you how an interest in
Darwin has been steadily growing in spite of the great majority of ignorant
people. People are beginning to want to know what Darwin really said, which
for me is an absolutely marvelous development. You know there's an
interesting side note that as a publisher you might be interested in. In the
first edition of the Origin of the Species there's not a single misprint.
What a document of the workmanship in 1859.
EDGE: Where do you think Darwinism is going to go in the next 50 years?
MAYR: Well, Darwinism will not have to do any going, because it's already
here. In the last 50 years, ever since the "Evolutionary Synthesis" of the
1940s, the basic theory of Darwinism has not changed, with perhaps one
exception, that is the question of the target of selection. What's the
object of a selective act? For Darwin, who didn't know any better, it was
the individual — and it turns out he was right.
An individual either survives or doesn't, an individual either reproduces or
doesn't, an individual either reproduces very successfully or it doesn't.
The idea that a few people have about the gene being the target of selection
is completely impractical; a gene is never visible to natural selection, and
in the genotype, it is always in the context with other genes, and the
interaction with those other genes make a particular gene either more
favorable or less favorable. In fact, Dobzhanksy, for instance, worked quite
a bit on so-called lethal chromosomes which are highly successful in one
combination, and lethal in another. Therefore people like Dawkins in England
who still think the gene is the target of selection are evidently wrong. In
the 30's and 40's, it was widely accepted that genes were the target of
selection, because that was the only way they could be made accessible to
mathematics, but now we know that it is really the whole genotype of the
individual, not the gene. Except for that slight revision, the basic
Darwinian theory hasn't changed in the last 50 years.
EDGE: Where do the generation of William Hamilton, George Williams and John
Maynard Smith fit in?
MAYR: Hamilton never denied the primacy of the individual. In the case of G.
C. Williams, I have come to the unhappy conclusion that not many of the
proposals of his best known book, Adaptation and Natural Selection (1996)
are valid.
EDGE: All right, so Darwinism isn't going to change in 50 years, but the
people writing about it certainly are changing.
MAYR: Every year one if not two books come out about Darwinian theory. Many
of them are favorable, which is fine, and yet as many others attempt to
improve or revise Darwin's original ideas, coming up with some so-called new
theory that is invariably total nonsense.
EDGE: I can imagine what you think about evolutionary psychology.
MAYR: Not necessarily! To tell the truth, I don't know much about it, but I
have heard there's a field called evolutionary epistemology. They use a very
simple Darwinian formula that can really be stated in a single sentence. If
you have a lot of variation, more than you can cope with, only the most
successful will remain. That is how things happen. In epistemology and
countless other fields. Variation and elimination.
EDGE: Who's notable in that field?
MAYR: Quite a few people though I can't recall their names right now.
Suffice it to say that there are many more evolutionary epistemologists in
Germany and Austria than in this country.
EDGE: It seems to me that Darwin is much better known in England than in the
United States. Books about Darwin sell well and people debate the subjects.
Here in America what passes for intellectual life doesn't necessarily
include reading and having an appreciation of Darwin.
MAYR: Yet the funny thing is if in England, you ask a man in the street who
the greatest living Darwinian is, he will say Richard Dawkins. And indeed,
Dawkins has done a marvelous job of popularizing Darwinism. But Dawkins'
basic theory of the gene being the object of evolution is totally
non-Darwinian. I would not call him the greatest Darwinian. Not even Maynard
Smith. Maynard Smith was raised in math and physics, and he was an airplane
engineer in the last war. For the most part, he still thinks like a
mathematician and engineer. His most successful contribution to evolutionary
biology has been applying so-called game theory to evolution. Personally I
have — and now I perhaps expose myself to a great deal of criticism, but
regardless — I have always been a little unhappy about that application of
game theory. What animal ever, in a confrontation, would say, now let me
figure it out, would it be better to be timid or would it be better to be
bold? That's not the way organisms think. You get — and somebody would have
to work this out since I'm not a mathematician — exactly the same result if
you have a population with every animal acting with a different mixture of
timidity and boldness. Individuals at one end of the curve are very timid
and have little boldness, individuals in the middle of the curve have an
appropriate mixture of timidity and boldness, and individuals at the other
end of the curve are very bold. Somewhere in between, in a given environment
with a given set of enemies and competitors, is the best mixture of the two
tendencies. You get the same results with game theory, but in my opinion,
the better solution has a much more biological, Darwinian approach.
EDGE: How can the evolution of human ethics be reconciled with Darwinism?
Doesn't natural selection always favor selfishness?
MAYR: If the individual were the only target of selection, this would indeed
be an inevitable conclusion. However, small social groups that compete with
each other, such as the groups of hunter-gatherers in our human ancestry,
were as groups also targets of selection. Groups, the members of which
actively cooperated with each other and showed much reciprocal helpfulness,
had a higher chance for survival than groups that did not benefit from such
cooperation and altruism. Any genetic tendency for altruism would therefore
be selected in a species consisting of social groups. In a social group,
altruism may add the to fitness. The founders of religions and philosophies
erected their ethical system on this basis.
EDGE: What important questions have I not asked you?
MAYR: One question that is very difficult one to answer is whether the
Darwinian framework is robust enough to remain the same for many years,
which I think it is, yes. The real question is what the burning issues in
evolutionary biology are today. To answer that you've got to get back into
functional biology. Take, for instance, a particular gene. Say this gene
makes amino acids that determine which side of the egg is to become the
anterior end of the larva and which will become the rear. We know that's
what it does but how it can do that is something about which we don't have
the slightest clue. That's one of the big problems, but it's in the realm of
proteins and functional biology rather than of DNA and evolutionary biology.
In evolutionary biology we have species like horseshoe crabs. The horseshoe
crab goes back in the fossil record over two hundred million years without
any major changes. So obviously they have a very invariant genome type,
right? . Wrong, they don't. Study the genotype of a series of horseshoe
crabs and you'll find there's a great deal of genetic variation. How come,
in spite of all this genetic variation, they haven't changed at all in over
two hundred million years while other members of their ecosystem in which
they were living two hundred million years ago are either extinct or have
developed into something totally different? Why did the horseshoe crabs not
change? That's the kind of question that completely stumps us at the present
time.
Then there are issues that no one besides a few biologists can fully fathom.
Like how and why do prokaryotes, bacteria that have no nucleus, differ in
their evolution from eukaryotes, organisms that do have an nucleus.
Eukaryotes have sexual reproduction, genetic recombination and well-formed
chromosomes, whereas prokaryotes have none of the above. So how do they get
genetic variation, which they must have in order to survive according to the
principle of natural selection? The answer is that prokaryotes exchange
genes with each other unilaterally; one bacterium injects a set of DNA into
another bacterium, which is an amazing process. Genes of course also go from
one chromosome to another via this old-fashioned process that all bacteria
use to reproduce. Beyond that, we don't really know how much such gene
transfer occurs in higher organisms.
EDGE: A number of years ago I was talking to a German publisher about a new
book on Darwinism. "I can't publish it," he said. "It's just too hot to
handle." Why is Darwin so dangerous, to use Dan Dennett's phrase?
MAYR: I have a good deal of contact with some very good young German
evolutionary biologists, and I'm constantly amazed how preoccupied they are
with political concerns. It's just that they have gone through a series of
political changes, from the Weimar Republic, to the Nazi period, Soviet
occupation, DDR, and finally a United Germany, and throughout this time,
everything has always been colored by politics. People got their jobs
because they were Nazis, or because they were anti-Nazis, and so forth. They
have to find a way to purge this from their system. In Germany, they
scrutinize all leaders in a field and check all the records as to whether
they had been Nazis, which Nazi organizations they might have belonged to,
whether they published either papers or books that indicate that they had
been Nazis or Communist, etc.
They think they have to do all this cleansing of science so that people
can't go and say well you didn't tell us that so-and-so was a Nazi or a
Communist. Scientists just have to cope with that. On the other hand,
translations of my books that were published in Germany have been very
successful. In fact, one of them is so successful that the German printing
has run out and I can't persuade the publisher to republish it. He asks why
he should publish another German edition of the book, when everybody reads
the English edition. Which is true.
EDGE: Recently the Frankfurter Allgemeine Zeitung began an initiative in
their Feuilletton (Arts and Culture) section to present popular science and
big scientific ideas to the public.
MAYR: I would say that generally you have far more food for the intellect in
foreign newspapers than you have in American ones, except a little bit in
papers like the Washington Post or The New York Times. It's remarkable; you
pick up a German newspaper and there's all sorts of good reading material in
it. Whereas we have very few such general interest articles in our papers.
The focus in our papers tends to be almost exclusively on news rather than
on education.
From:
www.edge.org
31st October 2001
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