One side can be wrong
Accepting 'intelligent design' in science classrooms would have
disastrous consequences, warn Richard Dawkins and Jerry Coyne.
It sounds so reasonable, doesn't it? Such a modest proposal. Why not
teach "both sides" and let the children decide for themselves? As
President Bush said, "You're asking me whether or not people ought to
be exposed to different ideas, the answer is yes." At first hearing,
everything about the phrase "both sides" warms the hearts of educators
One of us spent years as an Oxford tutor and it was his habit to choose
controversial topics for the students' weekly essays. They were
required to go to the library, read about both sides of an argument,
give a fair account of both, and then come to a balanced judgment in
their essay. The call for balance, by the way, was always tempered by
the maxim, "When two opposite points of view are expressed with equal
intensity, the truth does not necessarily lie exactly half way between.
It is possible for one side simply to be wrong."
As teachers, both of us have found that asking our students to analyse
controversies is of enormous value to their education. What is wrong,
then, with teaching both sides of the alleged controversy between
evolution and creationism or "intelligent design" (ID)? And, by the
way, don't be fooled by the disingenuous euphemism. There is nothing
new about ID. It is simply creationism camouflaged with a new name to
slip (with some success, thanks to loads of tax-free money and slick
public-relations professionals) under the radar of the US
Constitution's mandate for separation between church and state.
Why, then, would two lifelong educators and passionate advocates of the
"both sides" style of teaching join with essentially all biologists in
making an exception of the alleged controversy between creation and
evolution? What is wrong with the apparently sweet reasonableness of
"it is only fair to teach both sides"? The answer is simple. This is
not a scientific controversy at all. And it is a time-wasting
distraction because evolutionary science, perhaps more than any other
major science, is bountifully endowed with genuine controversy.
Among the controversies that students of evolution commonly face, these
are genuinely challenging and of great educational value: neutralism
versus selectionism in molecular evolution; adaptationism; group
selection; punctuated equilibrium; cladism; "evo-devo"; the "Cambrian
Explosion"; mass extinctions; interspecies competition; sympatric
speciation; sexual selection; the evolution of sex itself; evolutionary
psychology; Darwinian medicine and so on. The point is that all these
controversies, and many more, provide fodder for fascinating and lively
argument, not just in essays but for student discussions late at night.
Intelligent design is not an argument of the same character as these
controversies. It is not a scientific argument at all, but a religious
one. It might be worth discussing in a class on the history of ideas,
in a philosophy class on popular logical fallacies, or in a comparative
religion class on origin myths from around the world. But it no more
belongs in a biology class than alchemy belongs in a chemistry class,
phlogiston in a physics class or the stork theory in a sex education
class. In those cases, the demand for equal time for "both theories"
would be ludicrous. Similarly, in a class on 20th-century European
history, who would demand equal time for the theory that the Holocaust
So, why are we so sure that intelligent design is not a real scientific
theory, worthy of "both sides" treatment? Isn't that just our personal
opinion? It is an opinion shared by the vast majority of professional
biologists, but of course science does not proceed by majority vote
among scientists. Why isn't creationism (or its incarnation as
intelligent design) just another scientific controversy, as worthy of
scientific debate as the dozen essay topics we listed above? Here's
If ID really were a scientific theory, positive evidence for it,
gathered through research, would fill peer-reviewed scientific
journals. This doesn't happen. It isn't that editors refuse to publish
ID research. There simply isn't any ID research to publish. Its
advocates bypass normal scientific due process by appealing directly to
the non-scientific public and - with great shrewdness - to the
government officials they elect.
The argument the ID advocates put, such as it is, is always of the same
character. Never do they offer positive evidence in favour of
intelligent design. All we ever get is a list of alleged deficiencies
in evolution. We are told of "gaps" in the fossil record. Or organs are
stated, by fiat and without supporting evidence, to be "irreducibly
complex": too complex to have evolved by natural selection.
In all cases there is a hidden (actually they scarcely even bother to
hide it) "default" assumption that if Theory A has some difficulty in
explaining Phenomenon X, we must automatically prefer Theory B without
even asking whether Theory B (creationism in this case) is any better
at explaining it. Note how unbalanced this is, and how it gives the lie
to the apparent reasonableness of "let's teach both sides". One side is
required to produce evidence, every step of the way. The other side is
never required to produce one iota of evidence, but is deemed to have
won automatically, the moment the first side encounters a difficulty -
the sort of difficulty that all sciences encounter every day, and go to
work to solve, with relish.
What, after all, is a gap in the fossil record? It is simply the
absence of a fossil which would otherwise have documented a particular
evolutionary transition. The gap means that we lack a complete
cinematic record of every step in the evolutionary process. But how
incredibly presumptuous to demand a complete record, given that only a
minuscule proportion of deaths result in a fossil anyway.
The equivalent evidential demand of creationism would be a complete
cinematic record of God's behaviour on the day that he went to work on,
say, the mammalian ear bones or the bacterial flagellum - the small,
hair-like organ that propels mobile bacteria. Not even the most ardent
advocate of intelligent design claims that any such divine videotape
will ever become available.
Biologists, on the other hand, can confidently claim the equivalent
"cinematic" sequence of fossils for a very large number of evolutionary
transitions. Not all, but very many, including our own descent from the
bipedal ape Australopithecus. And - far more telling - not a single
authentic fossil has ever been found in the "wrong" place in the
evolutionary sequence. Such an anachronistic fossil, if one were ever
unearthed, would blow evolution out of the water.
As the great biologist J. B. S. Haldane growled, when asked what might
disprove evolution: "Fossil rabbits in the pre-Cambrian." Evolution,
like all good theories, makes itself vulnerable to disproof. Needless
to say, it has always come through with flying colours.
Similarly, the claim that something - say the bacterial flagellum - is
too complex to have evolved by natural selection is alleged, by a
lamentably common but false syllogism, to support the "rival"
intelligent design theory by default. This kind of default reasoning
leaves completely open the possibility that, if the bacterial flagellum
is too complex to have evolved, it might also be too complex to have
And indeed, a moment's thought shows that any God capable of creating a
bacterial flagellum (to say nothing of a universe) would have to be a
far more complex, and therefore statistically improbable, entity than
the bacterial flagellum (or universe) itself - even more in need of an
explanation than the object he is alleged to have created.
If complex organisms demand an explanation, so does a complex designer.
And it's no solution to raise the theologian's plea that God (or the
Intelligent Designer) is simply immune to the normal demands of
scientific explanation. To do so would be to shoot yourself in the
foot. You cannot have it both ways. Either ID belongs in the science
classroom, in which case it must submit to the discipline required of a
scientific hypothesis. Or it does not, in which case get it out of the
science classroom and send it back into the church, where it belongs.
In fact, the bacterial flagellum is certainly not too complex to have
evolved, nor is any other living structure that has ever been carefully
studied. Biologists have located plausible series of intermediates,
using ingredients to be found elsewhere in living systems. But even if
some particular case were found for which biologists could offer no
ready explanation, the important point is that the "default" logic of
the creationists remains thoroughly rotten.
There is no evidence in favour of intelligent design: only alleged gaps
in the completeness of the evolutionary account, coupled with the
"default" fallacy we have identified. And, while it is inevitably true
that there are incompletenesses in evolutionary science, the positive
evidence for the fact of evolution is truly massive, made up of
hundreds of thousands of mutually corroborating observations. These
come from areas such as geology, paleontology, comparative anatomy,
physiology, biochemistry, ethology, biogeography, embryology and -
increasingly nowadays - molecular genetics.
The weight of the evidence has become so heavy that opposition to the
fact of evolution is laughable to all who are acquainted with even a
fraction of the published data. Evolution is a fact: as much a fact as
plate tectonics or the heliocentric solar system.
Why, finally, does it matter whether these issues are discussed in
science classes? There is a case for saying that it doesn't - that
biologists shouldn't get so hot under the collar. Perhaps we should
just accept the popular demand that we teach ID as well as evolution in
science classes. It would, after all, take only about 10 minutes to
exhaust the case for ID, then we could get back to teaching real
science and genuine controversy.
Tempting as this is, a serious worry remains. The seductive "let's
teach the controversy" language still conveys the false, and highly
pernicious, idea that there really are two sides. This would distract
students from the genuinely important and interesting controversies
that enliven evolutionary discourse. Worse, it would hand creationism
the only victory it realistically aspires to. Without needing to make a
single good point in any argument, it would have won the right for a
form of supernaturalism to be recognised as an authentic part of
science. And that would be the end of science education in America.
Arguments worth having ...
The "Cambrian Explosion"
Although the fossil record shows that the first multicellular animals
lived about 640m years ago, the diversity of species was low until
about 530m years ago. At that time there was a sudden explosion of many
diverse marine species, including the first appearance of molluscs,
arthropods, echinoderms and vertebrates. "Sudden" here is used in the
geological sense; the "explosion" occurred over a period of 10m to 30m
years, which is, after all, comparable to the time taken to evolve most
of the great radiations of mammals. This rapid diversification raises
fascinating questions; explanations include the evolution of organisms
with hard parts (which aid fossilisation), the evolutionary "discovery"
of eyes, and the development of new genes that allowed parts of
organisms to evolve independently.
The evolutionary basis of human behaviour
The field of evolutionary psychology (once called "sociobiology")
maintains that many universal traits of human behaviour (especially
sexual behaviour), as well as differences between individuals and
between ethnic groups, have a genetic basis. These traits and
differences are said to have evolved in our ancestors via natural
selection. There is much controversy about these claims, largely
because it is hard to reconstruct the evolutionary forces that acted on
our ancestors, and it is unethical to do genetic experiments on modern
Sexual versus natural selection
Although evolutionists agree that adaptations invariably result from
natural selection, there are many traits, such as the elaborate plumage
of male birds and size differences between the sexes in many species,
that are better explained by "sexual selection": selection based on
members of one sex (usually females) preferring to mate with members of
the other sex that show certain desirable traits. Evolutionists debate
how many features of animals have resulted from sexual as opposed to
natural selection; some, like Darwin himself, feel that many physical
features differentiating human "races" resulted from sexual selection.
The target of natural selection
Evolutionists agree that natural selection usually acts on genes in
organisms - individuals carrying genes that give them a reproductive or
survival advantage over others will leave more descendants, gradually
changing the genetic composition of a species. This is called
"individual selection". But some evolutionists have proposed that
selection can act at higher levels as well: on populations (group
selection), or even on species themselves (species selection). The
relative importance of individual versus these higher order forms of
selection is a topic of lively debate.
Natural selection versus genetic drift
Natural selection is a process that leads to the replacement of one
gene by another in a predictable way. But there is also a "random"
evolutionary process called genetic drift, which is the genetic
equivalent of coin-tossing. Genetic drift leads to unpredictable
changes in the frequencies of genes that don't make much difference to
the adaptation of their carriers, and can cause evolution by changing
the genetic composition of populations. Many features of DNA are said
to have evolved by genetic drift. Evolutionary geneticists disagree
about the importance of selection versus drift in explaining features
of organisms and their DNA. All evolutionists agree that genetic drift
can't explain adaptive evolution. But not all evolution is adaptive.
Website explaining evolution in user-friendly fashion
Climbing Mount Improbable,
Richard Dawkin (illustrations by Lalla Ward), Penguin 1997
Evolution versus Creationism,
Eugenie C Scott, Greenwood Press, 2004
Richard Dawkins is Charles Simonyi professor of the public
understanding of science at Oxford University, and Jerry Coyne is a
professor in the department of ecology and evolution at the University