Toward a New Philosophy of Biology - review
by Jack P. Hailman
s most
readers of Auk are aware, Ernst
Mayr is one of the great ornithologists of this century, and he is one
of the foremost evolutionary biologists of our time as well. So when he
writes, it behooves us to read. Moreover, the present book was issued in
Mayr's ninth decade of life, reminding us of how long his contributions
have provided a guiding light of modern evolutionary thought.
Does biology need a new philosophy? Mayr begins by
arguing that it does, or perhaps that those who are not evolutionary
biologists need to recognize more fully that organic evolution is the
central theme of the biological sciences. So he embarks on a voyage through
natural selection, adaptation, Darwin's thinking, biological diversity,
species and speciation, and macroevolution, and he concludes with two essays
of historical perspective in order to show the way. This is not a new book,
in the sense of his 1982 opus, "The Growth of Biological Thought," but
rather a collection of previously published articles, book reviews, and
essays that have been edited to update them and to remove redundancy. The
works are arranged carefully and integrated with new bridge material to
provide the volume with a coherence too rarely found in this genre, so even
those who have read some of this material when it appeared will want to
consider it again within the new context. California produces high quality
wines year after year; the date on the label tells us the age of the wine,
but the vintage year is not so important. So let it be with Mayr.
Every essay in this book (there are nearly thirty) could
easily be the subject of its own review, as each deals with one or more
issues of real substance in evolutionary biology. There is no woodland
without its individual oaks, maples, pines and their ilk, but the trick is
to see the forest despite the trees. Whether those of us who are
evolutionary biologists like it or not, our science is not fully accepted in
the community of scholars for much the same reasons that we find it an
absorbing life's endeavor. Why is it that evolutionary biology is
"different," and how well has Mayr identified and dealt with the global
issues? I shall ignore largely historical problems such as vitalism, which
Mayr considers just at the start, and also the many smaller issues that do
not pierce the core. Forgive necessary oversimplification in the attempt to
treat the problem under just four rubrics: empiricism, reductionism,
historical load, and operationism.
In discussing evolution with biologists and other
scientists who profess reservations about our science, I have found that
they ask first after the evidence that selection is the driving force of
evolutionary change. Mayr asserts (p. 3) that "The Darwinian mechanism of
natural selection with its chance aspects and constraints is fully sufficient"
to explain teleological-like
aspects of evolution in particular, and indeed all the results of
evolution in general. A major stumbling block to understanding selection
processes is the unit
of selection or, as Mayr prefers, selection's target. Episodically
through the book, Mayr hammers home the point that the individual is the
target, and he has strong but deserved words about "the silent assumption
of the mathematical population geneticists that the gene is the unit of
selection" (p. 119). I find essay 7 on group selection somewhat angential
in focusing on different kinds of "groups" while losing track of the
"selection" part. The vagueness of the notion of "competition among
species" lies at heart here, for unless the species has a heritable emergent
property of its own that potentiates its continuance at the expense of
another species, "competition among species" is no more than competition
among individuals of different species. Still, logical problems aside,
Mayr nowhere confronts head-on the philosophical need in science for direct
empirical evidence. He cites (p. 96) Endler's 1986 book as providing the
"abundant evidence for the occurrence of natural selection in nature" but
that ambitious compilation reviews the works of true believers. What we
need is a philosophy for empirically testing the existence of selection in
such a way that one possible outcome of the test is outright rejection of
our beloved hypothesis.
Mentioning emergent properties brings me to the second of
four rubrics, for which we can use the term reductionism. As Mayr rightly
points out, many mechanistically inclined biologists see as a guiding
principle the reduction of life to "understood" mechanisms of physics and
chemistry. These colleagues fail to realize that the interactions among
parts provides the whole with properties that "emerge" with its existence.
As someone, perhaps Sir Arthur Eddington, said: we think we understand "two"
after making a thorough study of "one" because one and one are two, but we
forget that we must also make a thorough study of "and." Mayr does not
devote a lot of space to the reductionist problem per se, but he treats it
implictly throughout the book.
The third major issue that makes evolutionary biology
different from most sciences, although not uniquely so, is its pervasive
historical underpinning. There is a bridge in New York state unlike any over
which you have driven a vehicle. It is impossible to understand the design
of this bridge until you know that it was originally built as an aqueducto
carry the Erie Canal, and later modified as a roadbed. And so it is with
every organism on earth today: its ancestors were different, functional
organisms. Mayr confronts the historical constraints of evolution throughout
the book, although perhaps not with the verve and evidence I would have
desired. Essay 4, on the "Probability of Extraterrestrial Intelligent Life,"
is a particular gem. It shows us, as no other comparable section of the book,
how the evolutionary biologist arrives at vastly different predictions from
those of the physical scientist. The problem with most science fiction
movies is that they have the mindset of astronomer Donald Menzel rather than
that of biologist Ernst Mayr.
I have saved for last the bone that I am willing to
contend. Early in this century, physicists grappling with things that they
could not see came to realize this: an entity or process had communicable
meaning to fellow physicists only within the context of the operations by
which it was measured. From this origin, Nobel laureate Percy Bridgman
developed the philosophy of operationalism which today pervades most of
science. Evolutionary biology stands out like a very sore thumb. Most of
contemporary biology is so thoroughly operational that modern students take
it as a fact of life without realizing that things were not always this way.
Barely a generation ago, one could define the home range of an animal as
where it spent its time, but today one specifies the methods of recording
where it was and when, and then makes explicit how home range was calculated
from the data, say, by connecting spatial points to form the largest
possible polygon. What a philosophy of evolutionary biology needs, above all
else in my view, is operational approaches. We stake a difficult claim for a
legitimate science among peers when adaptedness is defined (p. 135) as "the
morphological, physiological, and behavioral equipment of a species or of a
member of a species that permits it to compete successfully with other
members of its own species or with individuals of other species and that
permits it to tolerate the extant physical environment." (For the curious,
an operational alternative may be found in my 1988 essay in "Evolutionary
Processes and Metaphors," edited by M. W. Ho and S. W. Fox.) Evolutionary
biology is so immensely complex that it has moved at a snail's pace toward
operational thinking. My complaint is not that Mayr himself has a
conceptual rather than operational intellect, for he was exactly appropriate
to his time, namely most of this century. My complaint is that this book
shows not the slightest hint that lack of operationism stands today as the
largest philosophical impediment to new advances in evolutionary biology.
To summarize the summary, "Towards a New Philosophy of
Biology" rates high in three of the four general issues I have dissected out
as being particularly crucial. It is, as the overworked closing sentiment
goes, "must" reading for anyone interested in evolutionary biology. And that,
I hope, includes us all. — JACK P. HAILMAN.
[ Jack P. Hailman, "Reviews,"
Auk
106 (October 1989): 751-752. ]
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