(originally published in
Science Jun 22 2001: 2257-2258)
If someone were to charge that textbooks present atomic theory using
evidence that is erroneous, misleading, and even fraudulent, and that we
should therefore question whether matter is composed of atoms, eyebrows
would be raised — at least at the accuser. If someone further claimed that
distinguished physicists crassly participate in this fraud to keep the
research dollars rolling in or to promote a materialist philosophical
agenda, scientists would be angry at the attempt to besmirch the
reputations of respected scholars. And if the same person proposed that
citizens should encourage local school boards to insert anti-atomic theory
disclaimers in science textbooks, discourage Congress from funding research
in atomic theory, and lobby state legislatures to restrict its teaching, it
is doubtful that such exhortations would receive much attention.
Such would be the fate of Jonathan Wells's call to arms in
Icons of
Evolution, if biological evolution were not substituted for atomic theory
in the above scenario. But rather than being ignored, Wells's book has
already inspired attacks on textbooks and at least one lawsuit against a
local school board (
1). Unlike atomic theory, evolution has obvious
theological implications, and thus it has been the target of concerted
opposition, even though the inference of common ancestry of living things
is as basic to biology as atoms are to physics.
Wells claims "students and the public are being systematically misinformed
about the evidence for evolution" because high school and college textbooks
rely on invalid or misleadingly interpreted "icons": the peppered moth, the
Miller-Urey experiment, vertebrate limb homology, Haeckel's embryos,
Archaeopteryx, Darwin's finches, the tree of life, four-winged fruit flies,
fossil horses, and the familiar fossils-to-modern-humans series of striding
men. These are well-known and frequently repeated examples of principles or
mechanisms of evolution, or episodes from the history of the field.
Textbooks use them because they communicate these basics clearly to
uninformed students. But Wells's premise that textbook examples are the
best evidence for evolution is wrong; evolution does not stand or fall on
whether a high school book simplifies an example of natural selection.
I examined the books reviewed by Wells and found that things are not
always as he portrays them. For example, textbooks don't uncritically rely
upon Haeckel or his drawings in their discussions of embryology. Only two
of the ten books reproduce Haeckel's embryo drawings, although all of them
present, in varying degrees of detail, the scientifically accepted
inference that comparative embryology reflects common ancestry. Some of
the other "icons" don't occur in most of his sample, and even when they do,
they are often accorded only a few paragraphs (
2).
Textbooks are, alas, far from perfect, but authors and publishers would
do little to improve their wares by altering their texts to suit Wells.
This is because Wells presents a systematically misleading view of
evolution. Individual sentences in Icons are usually technically correct,
but they are artfully strung together to take the reader off the path of
real evolutionary biology and into a thicket of misunderstanding. The
Cambrian explosion is supposed to be a "serious challenge to Darwinian
evolution" because "phyla and classes appear right at the start." Wells is
wrong to claim that the Cambrian appearance of major body plans supposedly
puts paleontologists into a tizzy; actually, they regard it simply as a
phenomenon yet to be explained. Unexplained is not unexplainable. More
misleading to nonscientists is the implication that most modern phyla and
classes occur in the Cambrian, which doesn't hold true for either animals
or plants. Wells neglects to mention that insects, amphibians, reptiles,
birds, and mammals are all post-Cambrian (and even Cambrian "fish" are
problematic). Wells correctly notes that chordates appear in the Cambrian,
and he correctly describes chordates as "tunicates, lancets, vertebrates."
But a layman hearing "vertebrates" is more likely to think of lions and
tigers and bears than of the very primitive, worm-like Cambrian chordate
Pikaia. Here, and with the other "icons," what Wells leaves out of his
discussion is often critical.
The author's discussion of the admittedly complex changes in populations
of the peppered moth is both incomplete and incorrect. He excoriates
textbooks for showing "fraudulent" photos of light and dark moths glued to
lichen-covered tree trunks. Wells argues that moths don't rest on tree
trunks and that lichens are not associated with moth color changes. But he
ignores research showing that moths rest on all parts of trees(including
the trunks) and that the color of the surface upon which moths alight is
what counts in predation. Dark moths against light backgrounds get nabbed,
whether or not lichens form those backgrounds. Textbooks show staged photos
of moths affixed to trees to illustrate crypsis of dark and light moths
against dark or light backgrounds; not unreasonably, photographers didn't
sit patiently by waiting for the right combinations of moths and
backgrounds. Researchers glued moths to trees to test whether birds
differentially prey upon moths that contrasted against their surface, an
experiment necessary to test the hypothesis of bird predation. This is not
fraud, it's research.
Space limits a full treatment of the book's errors and misdirections,
but as a physical anthropologist I must mention that Wells cites science
writer Henry Gee on the paucity of human fossils from 5 to 10 million years
ago. Yet he leaves out the abundance of such fossils over the last 5
million years, which is when humans evolved. Combining this deflection with
a 20-year-old citation from another journalist about the scarcity of human
remains, the lay reader may incorrectly conclude that the human fossil
record is unusually weak. Wells also ignores the many significant
discoveries of the past two decades.
Even more misleading, however, is Wells's steady drumbeat of accusation
of fraud, misconduct, deception, and incompetence against evolutionary
biologists and his claim that evolution is shoddy science maintained by
ideology rather than evidence. Although his targets have treated the book
with derision, Icons of Evolution has high potential to mislead the
nonscientific public, and scientists should be prepared to respond.
Notes
1.Arkansas legislation HB 2548 (2001) would ban textbooks which included
the icons. Patty Pulliam, a West Virginia parent, listed the "icons" in her
lawsuit against Kanawha County concerning alleged textbook inaccuracies.
Joe Baker, a senior at a Perkasie, PA, high school, is lobbying his
school board to insert icons disclaimers into the textbooks.
2.The set reviewed by Wells is a miscellany of ten high school and
college biology books, which curiously omits some best-selling texts and
other titles with comprehensive treatments of evolution. It is unclear
whether his results can be generalized. Wells's critique is discussed
further in A. Gishlick and E. C. Scott, "Do textbooks mislead students
about evolution? A look at Icons of Evolution,"
Reports of the NCSE, in press.