BYLINE: By Michael J. Behe; Michael J. Behe,
professor of biological sciences
at Lehigh University, is author of "Darwin's
Black Box: The Biochemical
Challenge to Evolution."
DATELINE: BETHLEHEM, Pa.
The debate leading the Kansas Board of
Education to abolish the requirement
for teaching evolution has about the same
connection to reality as the play
"Inherit the Wind" had to the actual Scopes
trial. In both cases complex
historical, scientific and philosophical issues
gave way to the simplifying
demands of the morality play. If the
schoolchildren of Kansas and other states
are to receive a good science education, however,
then we'll have to forgo the
fun of demonizing each other, take a deep breath
and start making a few
distinctions.
Regrettably, the action of the Kansas board
makes that much more difficult.
Not only are teachers there now discouraged from
discussing evidence in support
of Darwin's theory, results questioning it won't
be heard either.
For example, let's look at three claims of
evidence for Darwinian evolution
often cited by high school textbooks. First, as
the use of antibiotics has
become common, mutant strains of resistant
bacteria have become more common,
threatening public health. Second, darkcolored
variants of a certain moth
species evaded predation by birds because their
color matched the sooty tree
trunks of industrial England. Third, the embryos
of fish, amphibians, birds and
mammals look virtually identical in an early
stage of development, becoming
different only at later stages.
A relevant distinction, however, is that only
the first example is true. The
second example is unsupported by current
evidence, while the third is downright
false. Although light and darkcolored moths did
vary in expected ways in some
regions of England, elsewhere they didn't.
Further, textbook photographs
showing moths resting on tree trunks in the day,
where birds supposedly ate
them, run afoul of the fact that the moths are
active at night and don't
normally rest on tree trunks. After learning
about the problems with this
favorite Darwinian example, an evolutionary
scientist wrote in the journal
Nature that he felt the way he did as a boy when
he learned there was no Santa
Claus.
The story of the embryos is an object lesson
in seeing what you want to see.
Sketches of vertebrate embryos were first made in
the late 19th century by
Ernst Haeckel, an admirer of Darwin. In the
intervening years, apparently
nobody verified the accuracy of Haeckel's
drawings. Prominent scientists
declared in textbooks that the theory of
evolution predicted, explained and was
supported by the striking similarity of
vertebrate embryos. And that is what
generations of American students have learned.
Recently, however, an international team of
scientists decided to check the
drawings' reliability. They found that Haeckel
had, well, taken liberties: the
embryos are significantly different from each
other. In Nature, the head of the
research team observed that "it looks like it's
turning out to be one of the
most famous fakes in biology." What's more, the
embryonic stages shown in the
drawings are actually not the earliest ones. The
earliest stages show much
greater variation.
If I were teaching a high school biology
course, I certainly would want my
students to understand Darwin's theory of
evolution by natural selection, which
explains antibiotic resistance and a lot of other
things. I would want them to
know the many similarities among organisms that
are interpreted in terms of
common descent, as well as to understand the
laboratory experiments that show
organisms changing in response to selective
pressure.
But I would also want them to learn to make
distinctions and ask tough
questions. Questions we might discuss include
these:
If it's so difficult to demonstrate that small
changes in modern moths are
the result of natural selection, how confident
can we be that Darwinian
selection drove large changes in the distant
past? If supposedly identical
embryos were touted as strong evidence for
evolution, does the recent
demonstration of variation in embryos now count
as evidence against evolution?
If some scientists relied for a century on an
old, mistaken piece of data
because they thought it supported the accepted
theory, is it possible they
might even now give short shrift to legitimate
contrary data or
interpretations?
Discussing questions like these would help
students see that sometimes a
theory actively shapes the way we think, and also
that there are still
exciting, unanswered questions in biology that
may require fresh ideas.
It's a shame that Kansas students won't get to
take part in such a
discussion. We should make sure that the students
of other states do.
Emotions run very deep on the subject of
evolution, and while the morality
play generally casts religious people as the ones
who want to limit discussion,
some scientists on the "rational" side could fit
that role, too. But if we want
our children to become educated citizens, we have
to broaden discussion, not
limit it.
Teach Darwin's elegant theory. But also
discuss where it has real problems
accounting for the data, where data are severely
limited, where scientists
might be engaged in wishful thinking and where
alternative even "heretical"
explanations are possible.
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