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62 IGUANA  •  VOLUME 13, NUMBER 1  •  MARCH 2006 COMMENTARIES

Charles Darwin was not looking for trouble when he set off
on the Beagle in 1831. He most definitely could not have

imagined that, more than 150 years later and a third of the globe
away, judges in one of the world’s most advanced nations would
still be handing down rulings on his findings. Yet here we are,
and, as I write this in late December 2005, a federal judge once
again has had to inform the American public that the theory of
evolution is the only scientific explanation we have for how life
arose on this planet. The case in point involved the school board
of Dover, Pennsylvania, which in late 2004 adopted a policy
requiring students in science classes to be told about “intelligent
design” (ID) as “an explanation of the origin of life” (the text of
the statement can be found at http://www.cnn.com/2005/LAW/
12/20/intelligent.design.ap/). In striking down this requirement,
U.S. District Judge John E. Jones III, a Republican appointed
by President Bush, said that the school board’s decision was not
just unconstitutional but also dishonest: “We find that the sec-
ular purposes claimed by the Board amount to a pretext for the
Board’s real purpose, which was to promote religion in the pub-
lic school classroom.” He also had some strong words for the
members of the school board who created the policy, all eight of
whom subsequently lost their positions in recent elections and
were replaced by board members who promised to eliminate the
policy. He called the effort to force ID on the students a “breath-
taking inanity” and pointed out that “It is ironic that several of
these individuals, who so staunchly and proudly touted their
religious convictions in public, would time and again lie to cover
their tracks and disguise the real purpose behind the ID policy”
(the text of the decision can be found at http://www.pamd.
uscourts.gov/kitzmiller/kitzmiller_342.pdf).

Alas, that is not likely to be the end of the ongoing battle
to remove the teaching of evolution from the nation’s science
curricula, preferably to be replaced by material perceived to be
more compatible with Christian views of a particular flavor.
Proponents of ID correctly point out that evolutionary theory
does not explain everything. The struck-down Dover statement,
for example, says: “Gaps in the theory exist for which there is no
evidence.” In as much as our knowledge of anything is incom-
plete, they are absolutely correct. However, the underlying prob-
lem appears to be that many religious people in the U.S. believe
that accepting evolution somehow requires them to give up their
faith. The theory of evolution does make statements about how
life evolved once it appeared on Earth, and these statements now
have extensive support from biology, geology, and other fields of
science. They are not consistent with a literal interpretation of
the biblical creation story, but neither are parts of physics,
astronomy, geology, and other sciences. Nonetheless, science has

nothing to say about whether or not any particular deity exists,
and evolutionary theory does not make claims about the ulti-
mate source of life. As stated by the recently-deceased Pope John
Paul II, one can be a Christian and accept evolution: No inher-
ent contradiction exists between the two. In fact, many believ-
ers see no problem accepting evolution, and many scientists are
religious.

C O M M E N T A R I E S

Intelligent Design?
Gad Perry

Department of Range, Wildlife and Fisheries Management
Texas Tech University, Lubbock, Texas

Charles Darwin is often villified by those claiming evolution cannot
be true, and his theories are often disparaged by critics who pejoratively
call them “Darwinism,” suggesting that an acceptance of evolution is
comparable to a personality cult.

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IGUANA  •  VOLUME 13, NUMBER 1  •  MARCH 2006 63COMMENTARIES

What is ID? At heart, it claims that biological complexity
— proponents often cite processes such as blood clotting, which
rely on multiple biochemical pathways — shows that life could
not have evolved, but must rather have been formed by an
unnamed intelligent designer. In Pennsylvania, Judge Jones com-
plained about the “striking ignorance” of the education board
regarding the underpinnings of ID, but that does not necessar-
ily discredit the concept. However, Judge Jones also had some
clear words about the underlying scientific merit. ID is “not sci-
ence,” and “the fact that a scientific theory cannot yet render an
explanation on every point should not be used as a pretext to
thrust an untestable alternative hypothesis grounded in religion
into the science classroom or to misrepresent well-established sci-
entific propositions.” In fact, he ruled that ID is “creationism
relabeled.” ID cannot be science primarily because it does not
provide any means for scientists to test it. The few scientists who
advocate ID have been unable to provide scientifically valid ways
to evaluate their idea, and have consequently yet to receive exter-
nal support for such work or publish anything in the peer-

reviewed scientific literature. Moreover, let’s assume for a
moment that ID proponents are correct and evolutionary the-
ory is too weak to hold water. The scientific method would
require us to seek an alternative, but the Judge pointed out that
the argument made by ID proponents is “at bottom premised
upon a false dichotomy, namely, that to the extent evolutionary
theory is discredited, ID is confirmed.”

OK, ID is not science. Why have scientists throughout the
world long accepted evolution as the cornerstone of all biologi-
cal sciences? To appeal to scientists, an explanation has to have
predictive value. One must be able to make statements such as:
“If I am correct about the nature of gravity then this pen will
drop as soon as I let go of it.” Only a single case in which the
pen drifts up to the ceiling disproves our hypothesis, but no
matter how many times it falls, the possibility always remains
that next time, it will do something different. That is why sci-
entists should never claim to have proven anything. Still, we
have now dropped enough items and watched them crash to the
floor that no sane person will step off the roof with the hope of
floating up. Gravity has so much predictive power that we now
call it a theory and take it for granted, even though physicists
still do not understand why it works.

Our understanding of evolution also allows us to make
testable predictions about the world around us. For example, a
single solid case in which a fossil of a mammal is found in a layer
preceding the evolution of fish would refute our understanding
of the process, because fish are thought to be ancestral to mam-

“As a Christian, a trained engineer and scientist, and a professor at
Emory University, I am embarrassed by … [attempts] to censor and
distort the education of Georgia’s students,” said former President
Jimmy Carter, a Baptist and Nobel prize winner, in 2004 in response
to suggestions that the word “evolution” should be banned from the
state’s curriculum. Additional information can be found at the White
House web site (http://www.whitehouse.gov/history/presidents/
jc39.html).

This series of “family trees” shows how natural selection has affected
anoles on the islands of the Greater Antilles. A. When only physical
characteristics are considered, species cluster according to ecomorph
class (a descriptive suite of characters that reflects an animal’s lifestyle
or niche) regardless of geographic affinities. Letters indicate the islands
on which a species is found (C = Cuba; H = Hispaniola; J = Jamaica;
P = Puerto Rico). B. In sharp contrast with A., this tree, which was
generated using molecular data (DNA sequences), indicates frequent
transitions among ecomorph classes and a much stronger correlation
between close relationships and geographic affinities. In other words,
species found on the same island are much more likely to be closely
related than species on different islands that might share very similar
appearances as a consequence of being in the same ecomorph class.
This example of how evolutionary methods can shed insights on eco-
logical relationships was adapted from Losos et al. (1998. Science 279:
2115–2118).

Michelangelo’s Sistine Chapel illustrates the negative consequences of
curiosity. The church in Michelangelo’s time, like many authoritarian
regimes, very actively stifled any free-thinking, believing that curiosity
would foster doubts and lead to inquiries, all of which are threatening
to the status-quo.

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64 IGUANA  •  VOLUME 13, NUMBER 1  •  MARCH 2006 COMMENTARIES

mals. In fact, evolutionary biologists predicted the evolution of
drug-resistant germs and pesticide-resistant insects. Both are
large and well-publicized problems now, especially with the
prevalence of drug-resistant diseases such as tuberculosis being
on the rise. Evolutionary biologists also were the first to point
out that a disease such as avian flu, that currently attacks birds

in Asia, could easily evolve into a pandemic killing many mil-
lions of people all over the world — a contingency many coun-
tries, including the U.S., are investing billions of dollars to
address. Evolutionary biologists made predictions about the
mechanisms by which evolution proceeds long before the tools
for studying evolutionary developmental biology were available
to test them. Cutting-edge research from recent years has shown
how different-looking morphological structures could evolve
from similar underlying genetic building blocks. Scientists used
to think that eyes had evolved many times, giving rise to the dif-
ferent structures shown by insects and mammals, for example.
Recent discoveries have identified a single gene, called Pax-6,
which is involved in the formation of eyes in creatures as diverse
as fruit flies, squid, and humans. Apparently, all modern eyes,
no matter how different-looking, have evolved from a primitive

Evolutionary studies have confirmed Cuba as the origin of all species
in the Anolis carolinensis group (top); adapted from Glor et al. (2005.
Molecular Ecology 14: 2419–2432). Most dispersal routes follow pre-
vailing winds and currents; a notable exception is A. longiceps on
Navassa Island (left; no. 6 on the map), which is to the southeast of
Cuba. Over-water dispersal of the ancestors of A. longiceps was pre-
sumably facilitated by the counter-clockwise winds associated with hur-
ricanes (Powell. 1999. Caribbean Journal of Science 35: 1–13).

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IGUANA  •  VOLUME 13, NUMBER 1  •  MARCH 2006 65COMMENTARIES

organ found in a shared ancestor. As one final demonstration of
its utility, an understanding of evolutionary processes allows us
to use DNA to determine paternity, identify bodies, and assign
blame in criminal cases.

For those of us engaged in conservation, an understanding
of evolution is especially important. “Everybody knows” small
populations are at risk, but evolutionary biology explains why,
and further predicts how fast they might decline. We all recog-
nize that habitat fragmentation is undesirable, but only because
evolutionary theory allows us to analyze the potential genetic
consequences. Without the concept of coevolution, how would
we understand the strong dependence some plants have on par-
ticular pollinators, or why closely related species of parasites
often infect closely related hosts? Evolutionary theory also tells
us that invasive species are going to adapt to their novel envi-
ronments and become even more problematic, something man-
agers have to know when designing responses to that problem.
Finally, evolution is responsible for the many species of iguanas
and other insular species in the Caribbean, and an understand-
ing of DNA and the varying rates at which different kinds of

DNA evolve allows us to identify unique populations deserving
of extra protection.

The now-defeated Dover board defined a theory as “a well-
tested explanation that unifies a broad range of observations.”
By every measure available to us, evolution is not “just a theory”
— as one so often hears it disparagingly called — but is instead
an extremely robust and successful theory whose predictive value
has repeatedly been demonstrated. Of course, there are many
things we do not yet know. As a leading proponent of ID
pointed out after the Pennsylvania ruling, “A thousand opinions
by a court that a particular scientific theory is invalid will not
make that scientific theory invalid … It is going to be up to the
scientists who are going to continue to do research in their labs
that will ultimately determine that.” Some details of evolution-
ary theory will doubtlessly need to be reformulated as more
information comes in — for that’s how science works. The time
has come for religious zealots to leave their beliefs outside the
science classroom, which is properly devoted to studying natu-
ral explanations of the phenomena that rule our lives.
Evolutionary theory is unlikely to be replaced any time soon.

Understanding evolution can have important practical applications. Doonesbury © 2005 G.B. Trudeau. Reprinted with permission of Universal
Press Syndicate. All rights reserved.

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