David N. Reznick is professor of biology at the University of California, Riverside. His latest book is "The Origin Then and Now: An Interpretive Guide to the Origin of Species."

Editor's Note: The so-called Scopes Monkey Trial concluded on July 21, 1925, making this year the trial's eighty-fifth anniversary. HNN is pleased to present two articles, one by an evolutionary biologist, the other by a humanist, to mark the occasion.

On weekend mornings I get up at sunrise and run up the Box Springs Mountains. Lately there has been a marine layer of clouds that lock in cold, moist air at lower elevations. As I run up through the cloud layer I can feel the clouds dissipate and see them break up into a fine, particulate mist as the sun shines through, then I emerge into a warm, sunny day at higher elevations. Since the valleys are completely obscured by the cloud layer, I can run along the crest line and imagine that I am in a remote wilderness, rather than on an island surrounded by suburbs. Two Sundays ago, as I descended back into the clouds, I saw a man ahead of me wearing a black t-shirt with “Science Rules!” printed on the back in bold, white letters. I don’t like to stop, but I could not resist asking about him or the t-shirt. He explained that he was a member of the Skeptic Society and that they occasional met on Sunday mornings to take hikes together. When I mentioned that I was an evolutionary biologist, he replied that, while he was a fan of science, he had problems with evolution. That was the end of my run. I asked him about his doubts and tried to answer his questions as we walked down together. Answering all his questions was easy since they were mostly familiar—“If evolution is gradual, then why are species so distinct?” or “How can a gradual process explain the origin of complex traits?” A peculiar attribute of evolutionary biology is that, even though it is an arcane science, many people have opinions about it, much more so, I think, than any other science. Why?

The occasion of the eighty-fifth anniversary of the Scopes trial offers some basis for reflection on the peculiar status of evolution. The trial was neither the beginning nor the end of the public debate over Darwin’s theory. We could place the beginning at the British Association for the Advancement of Science meeting that took place in Oxford in 1860, where Thomas Huxley and Bishop Samuel Wilberforce squared off on a public debate of the newborn theory of evolution by natural selection. The end of the debate is not in sight. The Scopes trial instead stands out as a benchmark that adds an American flavor to the controversy, which is to blur the division between science and religion in the public classroom. The near-term impact was for evolution to recede from science textbooks. Evolution did not come back in force until the post-Sputnik era, when the U.S. enhanced science and math education. This renaissance was short-lived and we have returned to the conditions that surrounded the Scopes trial.

So why is there such persistent controversy about evolution? At one level, we always hear that evolution is “just a theory.” This descriptor reveals a misunderstanding of the word “theory.” An unabridged dictionary offers several definitions of the word, with the appropriate one being dependent on context. In colloquial use, theory means speculation, but when used by scientists it means something like the articulation of a general principle that unites a diversity of phenomena under a single explanatory framework, such as Newton’s theory of universal gravitation. Darwin’s evolution by natural selection fulfills this goal. But the source of skepticism cannot be this simple. We all have heard of the theory of relativity, but we never see headlines like “Relativity—fact or fiction?” No one debates how the theory of relativity is taught in physics classes, nor is a physicist ever likely to bump into some stranger who expresses doubts about relativity. Some argue that skepticism about evolution is instead a measure of the inadequacy of science education. We can certainly do better in teaching science in our public schools, but this is not a good answer either, since all science can be better taught but no other area of science attracts such scrutiny.

A better answer, for which the Scopes trial is a symbol, is that the theory of evolution has been a consistent target of religiously motivated propaganda campaigns. Two well-funded institutes—the Creation Science Institute and the Discovery Institute—are devoted to churning out anti-evolution literature. The former arose in the 1960s and was built on “creation science,” while the latter arose to promote “intelligent design” after creation science was discredited by repeated court battles. The Dover trial revealed that intelligent design is just thinly disguised creation science. A product of the efforts of these institutes and those who support their views is that most people have heard dozens of times that there is something wrong with the theory of evolution, so it is natural to be skeptical about evolution.

The arguments against evolution have changed little over the decades. A persistent favorite is the mystery of the origin of complex, seemingly perfect structures like the eye. The argument today is very much the one made by Archdeacon William Paley in his Natural Theology (1802), which is that when we see evidence of design in nature, then we also see evidence for the existence of the designer. Now that the genetic basis of eye development is emerging from the fog, some have shifted instead to the mystery of the bacterial flagellum. Otherwise, the argument is the same. These arguments are reinforced by occasional scientists or philosophers and historians of science who argue that natural selection is the product of circular reasoning. All of these arguments have been refuted, but they persist.

A consequence of the controversy is that every time I step in front of a lecture hall full of students, I can count on many of them being doubters of the theory. It also means that evolutionary biologists will often encounter people who have thought about and are skeptical of evolution, so evolutionary biologists feel more of a need to explain themselves in a way than those who represent any other branch of science. One response was to write books that counter the arguments against evolution, to little effect. The bicentennial of Darwin’s birth has brought on a different wave of books. Evolutionary biologists are now more inclined to just write about evolution and to present it in a light that makes it more accessible to a general public. We are all wondering who the silent majority really is and how to reach them. Our hope is that some of them are skeptics who are willing to read a well-crafted presentation of science and evaluate its virtues with an open mind. Some historians and philosophers have helped by articulating how evolution fits in to the development of science, but also by dealing with the relationship between science and religion as a topic for the humanities classroom, rather than the science classroom. We need the help, so I encourage my colleagues in the humanities to expand these efforts.

HNN Special: The Scopes Trial at 85