New York Times, August 13, 1999, Friday, Page A21, Editorial Desk

Teach Evolution and Ask Hard Questions


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.

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.