Evolution
as Fact and Theory
STEPHEN
JAY GOULD
Gould’s
career as a scientist at Harvard from 1967 until his death
in 2002 ended with the publication of his magnum opus, The
Structure of Evolutionary Theory. In addition to his
treasured teaching and remarkable research, he wrote each
month for 25 years a column, “This View of Life,”
for Natural History, the magazine of the American
Museum of Natural History. The wisdom of this leading participant
in major scientific controversies was evident whenever he
spoke at Cambridge Forum events in the same Unitarian Meeting
House in Harvard Square where earlier Ralph Waldo Emerson
delivered his epochal address on “The American Scholar.”
This
article is abridged from Speak Out Against the New Right
edited by Herbert F. Vetter (Boston:
Beacon Press, 1982)
Kirtley Mather, who died last year at age 89, was a pillar
of both science and the Christian religion in America and
one of my dearest friends. The difference of half a century
in our ages evaporated before our common interests. The
most curious thing we shared was a battle we each fought
at the same age. For Kirtley had gone to Tennessee with
Clarence Darrow to testify for evolution at the Scopes trial
of 1925. When I think that we are enmeshed again in the
same struggle for one of the best documented, most compelling
and exciting concepts in all of science, I don't know whether
to laugh or cry.
According to idealized principles of scientific discourse,
the arousal of dormant issues should reflect fresh data
that give renewed life to abandoned notions. Those outside
the current debate may therefore be excused for suspecting
that creationists have come up with something new, or that
evolutionists have generated some serious internal trouble.
But nothing has changed; the creationists have not a single
new fact or argument. Darrow and Bryan were at least more
entertaining than we lesser antagonists today. The rise
of creationism is politics, pure and simple; it represents
one issue (and by no means the major concern) of the resurgent
evangelical right. Arguments that seemed kooky just a decade
ago have reentered the mainstream.
Creationism
Is Not Science
The
basic attack of the creationists falls apart on two general
counts before we even reach the supposed factual details
of their complaints against evolution. First, they play
upon a vernacular misunderstanding of the word "theory"
to convey the false impression that we evolutionists are
covering up the rotten core of our edifice. Second, they
misuse a popular philosophy of science to argue that they
are behaving scientifically in attacking evolution. Yet
the same philosophy demonstrates that their own belief is
not science, and that "scientific creationism"
is therefore meaningless and self-contradictory, a superb
example of what Orwell called "newspeak."
In the American vernacular, "theory" often means
"imperfect fact" —part of a hierarchy of
confidence running downhill from fact to theory to hypothesis
to guess. Thus the power of the creationist argument: evolution
is"only" a theory, and intense debate now rages
about many aspects of the theory. If evolution is less than
a fact, and scientists can't even make up their minds about
the theory, then what confidence can we have in it? Indeed,
President Reagan echoed this argument before an evangelical
group in Dallas when he said (in what I devoutly hope was
campaign rhetoric): "Well, it is a theory. It is a
scientific theory only, and it has in recent years been
challenged in the world of science—that is, not believed
in the scientific community to be as infallible as it once
was."
Well, evolution is a theory. It is also a fact. And facts
and theories are different things, not rungs in a hierarchy
of increasing certainty. Facts are the world's data. Theories
are structures of ideas that explain and interpret facts.
Facts do not go away when scientists debate rival theories
to explain them. Einstein's theory of gravitation replaced
Newton's, but apples did not suspend themselves in mid-air
pending the outcome. And human beings evolved from apelike
ancestors whether they did so by Darwin's proposed mechanism
or by some other, yet to be discovered.
Moreover, "fact"
does not mean "absolute certainty." The final
proofs of logic and mathematics flow deductively from stated
premises and achieve certainty only because they are not
about the empirical world. Evolutionists make no claim for
perpetual truth, though creationists often do (and then
attack us for a style of argument that they themselves favor).
In science, "fact" can only mean "confirmed
to such a degree that it would be perverse to withhold provisional
assent." I suppose that apples might start to rise
tomorrow, but the possibility does not merit equal time
in physics classrooms.
Evolutionists have been clear about this distinction between
fact and theory from the very beginning, if only because
we have always acknowledged how far we are from completely
understanding the mechanisms (theory) by which evolution
(fact) occurred. Darwin continually emphasized the difference
between his two great and separate accomplishments: establishing
the fact of evolution, and proposing a theory—natural
selection—to explain the mechanism of evolution. He
wrote in The Descent of Man: "I had two distinct objects
in view; firstly, to show that species had not been separately
created, and secondly, that natural selection had been the
chief agent of change . . . Hence if I have erred in . .
. having exaggerated its | natural selection's] power .
. . I have at least, as I hope, done good service in aiding
to overthrow the dogma of separate creations."
Thus Darwin acknowledged the provisional nature of natural
selection while affirming the fact of evolution. The fruitful
theoretical debate that Darwin initiated has never ceased.
From the 1940s through the 1960s, Darwin's own theory of
natural selection did achieve a temporary hegemony that
it never enjoyed in his lifetime. But renewed debate characterizes
our decade, and, while no biologist questions the importance
of natural selection, many now doubt its ubiquity. In particular,
many evolutionists argue that substantial amounts of genetic
change may not be subject to natural selection and may spread
through populations at random. Others are challenging Darwin's
linking of natural selection with gradual, imperceptible
change through all intermediary degrees; they are arguing
that most evolutionary events may occur far more rapidly
than Darwin envisioned.
Scientists regard debates on fundamental issues of theory
as a sign of intellectual health and a source of excitement.
Science is—and how else can I say it?—most fun
when it plays with interesting ideas, examines their implications,
and recognizes that old information may be explained in
surprisingly new ways. Evolutionary theory is now enjoying
this uncommon vigor. Yet amidst all this turmoil no biologist
has been led to doubt the fact that evolution occurred;
we are debating how it happened. We are all trying to explain
the same thing: the tree of evolutionary descent linking
all organisms by ties of genealogy. Creationists pervert
and caricature this debate by conveniently neglecting the
common conviction that underlies it, and by falsely suggesting
that we now doubt the very phenomenon we are struggling
to understand.
Using another invalid argument, creationists claim that
"the dogma of separate creations," as Darwin characterized
it a century ago, is a scientific theory meriting equal
time with evolution in high school biology curricula. But
a prevailing viewpoint among philosophers of science belies
this creationist argument. Philosopher Karl Popper has argued
for decades that the primary criterion of science is the
falsifiability of its theories. We can never prove absolutely,
but we can falsify. A set of ideas that cannot, in principle,
be falsified is not science.
The entire creationist argument involves little more than
a rhetorical attempt to falsify evolution by presenting
supposed contradictions among its supporters. Their brand
of creationism, they claim, is "scientific" because
it follows the Popperian model in trying to demolish evolution.
Yet Popper's argument must apply in both directions. One
does not become a scientist by the simple act of trying
to falsify another scientific system; one has to present
an alternative system that also meets Popper's criterion—it
too must be falsifiable in principle.
"Scientific creationism" is a self-contradictory,
nonsense phrase precisely because it cannot be falsified.
I can envision observations and experiments that would disprove
any evolutionary theory I know, but I cannot imagine what
potential data could lead creationists to abandon their
beliefs. Unbeatable systems are dogma, not science. Lest
I seem harsh or rhetorical, I quote creationism's leading
intellectual, Duane Gish, Ph.D., from his recent (1978)
book Evolution? The Fossils Say No! "By creation
we mean the bringing into being by a supernatural Creator
of the basic kinds of plants and animals by the process
of sudden, or fiat, creation. We do not know how the Creator
created, what processes He used, for He used processes which
are not now operating anywhere in the natural universe
[Gish's italics]. This is why we refer to creation as special
creation. We cannot discover by scientific investigations
anything about the creative processes used by the Creator."
Pray tell, Dr. Gish, in the light of your last sentence,
what then is "scientific" creationism?
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