The case of the peppered moth illusion - science teaching needs to challenge traditional views of science

Whole Earth,  Spring, 1999  by Craig Holdrege

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Even more baffling, birds do not fly or feed at night and, as we don't know which kind of moths prefer light traps (more females than males? more darks than lights?), there is no correlation between contrived, daytime results and the conclusions drawn from equally contrived observations made at night.

SEEING WHAT WE BELIEVE?

Stephen Jay Gould and Richard Lewontin, highly regarded contemporary evolutionary scientists, are highly critical of the "adaptationist programme," as they call it; and one of their reasons is "its unwillingness to consider alternatives to adaptive stories." If Kettlewell hadn't been so convinced of the truth of bird predation affecting peppered moth evolution, he might have left more room for alternative explanations.

In the moth/bird-predation example we see how strongly a theoretical framework informs the interpretation of the facts. When scientists have, as Lynn Margulis puts it in Slanted Truths, "an uncritical acceptance of the mesmerizing concept of adaptation," there is a real danger of seeing what one believes. We get oversimplified portrayals that turn science into dogma.

If we are truly interested in understanding phenomena, and not in seeing our own preconceptions in them, we must become more aware of our thinking--make it a more adequate and adaptable instrument of understanding. In performing an experiment, we are creating a simple and relatively transparent situation which is, of course, not identical to a natural phenomenon. We should be extremely wary of drawing conclusions that go beyond the experiment itself. Kettlewell's field experiments seem to show that birds feed on moths released onto trees in the early morning. But since the moths are not normally found on lower tree trunks during the day, Kettlewell has created (as all experiments do) an artificial situation. We need to hold back conclusions and consider alternative explanations--the guessable and the unknown. Instead of viewing experiments as a way to prove or disprove an idea, we should come to see them as a way of interacting with phenomena. Experiments help us clarify our ideas, discover phenomena, formulate new questions, and look with new eyes into nature. We can use hypotheses as a way to get started, well knowing that they need to be left behind when we confront the true phenomena, and begin to practice a flexibility of thought. The peppered moth becomes more and more like a deep question, rather than an instance of general theory.

IMPLICATIONS FOR SCIENCE EDUCATION

In 1997 I taught the full picture of the peppered moth to high school seniors at a school in upstate New York whose curriculum is not state-regulated. The students were fascinated by the moth and by the contrast between the simple story and the complex reality; by the process of discovery and transformation. This historical, case-study approach demands more classroom time, and more research on the part of the teacher, than does providing general overviews of material. But it brings science alive. We learn how scientists make observations, formulate ideas and questions, and test their hypotheses through experiments. We see how contradictions arise, how concepts become rigid, and then--often in the face of resistance--how they are modified or even dropped. Young people (if we have not corrupted them too much) are open-minded and interested in the world. Certainly it makes sense for them to study science (and of course other disciplines) not as codified knowledge to be memorized, but as a way of interacting with nature that leads to insights, and to ever-new questions. They begin to think of science as a process occurring in a historical context. What could be a more appropriate way to learn about the science of life, of biology?