"The New York Times" 
December 16, 2001

'What Evolution Is': A Friendly Textbook

By PAUL RAEBURN

When you are 97 years old, and for six or seven decades you've been at the
center of nearly every dispute in evolution -- and have helped settle several of
them -- it's O.K. to make highfalutin claims for your new book. Ernst Mayr,
emeritus professor at Harvard and the author of ''What Evolution Is,'' claims in
the preface that this book surpasses all of the existing books on evolution. The
others, he says, ''are rather poorly organized and fail to present a concise,
reader-friendly account.'' Many are too technical, and none ''quite fills the
niche I have in mind.'' His book is addressed both to readers who want to know
more about evolution and to those who reject evolution but may want to learn
more ''if for no other reason than to be able to better argue against it.'' 

After I'd read that, I continued with high hopes. Here I thought I'd find the
unerring hand of a master, leading me expertly through the subtleties of
evolutionary theory. As it turns out, I should have skipped the preface. Mayr
set goals for this book that probably couldn't be met by anyone. He did,
however, write a very good book. 

Mayr has been called ''the greatest living evolutionary biologist'' by his
colleague Stephen Jay Gould. He has held that honorary title for more than half
a century: one of his most important contributions came in 1942, when he
published ''Systematics and the Origin of Species,'' which incorporated
genetics, ecology and paleontology into what has become the modern view of
evolution. And Mayr has been hard at it ever since, turning out two books this
year alone. (Besides this one, he has a 500-page scholarly work on the birds of
Melanesia, written with Jared M. Diamond.) 

''What Evolution Is'' is not the last book you will ever need on the subject.
Too much jargon still clings to Mayr's professorial tweed jacket, and he's not
too generous with the anecdotes and oddities you will find in most popular works
on evolution. But if you approach the book without unrealistic expectations, you
will find a wise and illuminating account that sorts out the complexities of
evolution with insight and an authority often lacking elsewhere. The book makes
some modest demands on its readers. Mayr isn't interested in an audience that
won't take a little time to think. I came to think of ''What Evolution Is'' as a
friendly textbook, less daunting and less exhaustive than the real thing, and a
lot easier to carry on the subway. 

One of the first things Mayr does is to establish what made Darwin Darwin.
Evolution was in the air long before the publication, in 1859, of ''On the
Origin of Species.'' Why, then, did Darwin's work set off a revolution? His
grandfather, Erasmus, had written about the ability of species to change or
become extinct, sometimes putting his ideas down in the form of erotic poetry.
The naturalist Jean-Baptiste Lamarck had proposed that the world was not static
but changing, with simpler organisms progressing to more complex animals and man
at the top of the scale. The word ''evolution,'' once used to describe the
development of the egg, had already been commandeered to describe the
development of life on earth. These early notions of evolution arose to explain
the growing evidence that the world was changing and that some animals had
become extinct. Until Darwin, however, these changes were thought to be entirely
in the hands of the Creator. 

When Darwin returned to England in October 1836, after nearly five years
traveling the world aboard the Beagle, he brought with him a wealth of specimens
and observations that would vastly extend those earlier, tentative observations
of evolution. All the parts of a revolutionary new theory of evolution were
spread before him, but it took him 23 years of research and study to assemble
them and describe the results. The publication of ''On the Origin of Species,''
Mayr says, ''represents perhaps the greatest intellectual revolution experienced
by mankind.'' Darwin ''proposed an explanation for evolution that did not rely
on any supernatural powers or forces. He explained evolution naturally, that is,
by using phenomena and processes that everybody could daily observe in nature.''
The book ''almost single-handedly effected the secularization of science.'' 

Mayr backs that up with a deft analysis of what Darwin actually said. Indeed,
Darwin did more than merely demonstrate that the world's organisms are changing.
That was only one of five separate theories he put forth. Two of them were
widely accepted almost immediately. One was the extensive evidence that species
are changing, that the world is not constant. And the other was the idea that
different species have descended from common ancestors. Men did not in fact
descend from apes, at least not the apes living today. Humans and modern apes
descended from an ancestor that had attributes common to both. 

The acceptance of those ideas is what Mayr calls the first Darwinian revolution.
The three other theories outlined by Darwin were not accepted until the 1940's,
Mayr says. At that time, in what he calls the second Darwinian revolution, most
uthorities came to agree with Darwin's remaining theories. One explained the
gradual nature of evolution, a second outlined the reasons behind the
multiplication and diversity of species and the third was the principle of
natural selection. 

The gradual nature of evolution was explained by focusing on what Mayr says is
one of its key concepts: the idea that it occurs in populations, not individual
organisms. Before Darwin, naturalists worked hard to determine what
characteristics made up an ideal specimen of, say, a species of butterfly -- to
pin down the platonic essence of that particular creature. 

Darwin recognized that there is no perfect specimen -- that the naturally
occurring variations in populations are crucial to the operation of evolution.
Some in any population will have characteristics that give those individuals a
tiny advantage in terms of survival. One of Mayr's pointed insights is that
natural selection is really a process of elimination, not selection. In any
given population, most individuals will be fit enough to survive, and a few will
not. The attributes that confer survival advantages will gradually become more
common among the population. It happens slowly over many generations, producing
the kind of gradual change seen in the fossil record. According to Mayr, many
evolutionists did not accept this explanation for gradualism until the 1940's. 

Mayr's parsing of Darwin's various theories, and his description of how they
eventually triumphed, are among the many virtues of this book. I've wandered
through a number of books on evolution over the years, but none have spelled all
that out so clearly. 

In the end, Mayr provides as convincing a testament to Darwin's genius as you
are likely to find. Virtually all of modern evolutionary theory was contained in
that single book Darwin published in 1859. There is, however, one outstanding
exception. What, Darwin wondered, was the source of the variability in
populations? ''This is what puzzled Darwin all of his life, but in spite of all
his efforts he never found the answer,'' Mayr writes. 

What Darwin needed was the science of genetics, which, unknown to him or anyone
else in the scientific world, was then being born about 800 miles from London in
what is now the Czech Republic. There, Gregor Mendel was deducing the principles
of inheritance from painstaking work in a garden of pea plants. Mendel presented
his findings in 1865, only six years after the publication of ''On the Origin of
Species'' and 17 years before Darwin's death. If Darwin had known of Mendel's
work, he might have solved that one remaining puzzle. 

As Robin Marantz Henig tells it in her 2000 book, ''The Monk in the Garden,''
Darwin came very close. Mendel, desperate for others to pay attention to his
work, sent reprints of his paper to several prominent scientists in Europe.
After Darwin's death, a copy of Mendel's reprint was found in Darwin's library.
The printed pages had been folded but not cut apart. Darwin apparently never
looked at it. 

Paul Raeburn, a senior writer at Business Week, is working on a book on mental
illness in children.

Oryginal: http://www.nytimes.com/2001/12/16/books/review/16RAEBURT.html

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