Teaching Evolution in Tennessee

The state of Tennessee is about to have a new law that impacts the teaching of science in their public schools. Here's how the National Center for Science Education (NCSE) describes the law.

Nicknamed the "monkey bill," HB 368 would, if enacted, encourage teachers to present the "scientific strengths and scientific weaknesses" of topics that arouse "debate and disputation" such as "biological evolution, the chemical origins of life, global warming, and human cloning."

It doesn't take a mental giant to see where the Tennessee legislators are coming from. They want to support teachers who challenge evolution in the classroom. Most of those teachers will, of course, be creationists of one form or another.

But here's the problem. Those ignorant legislators have been very clever to avoid mentioning religion or creationism. On the surface, the new law looks perfectly reasonable.After all, who wouldn't want students to learn both the scientific strengths and weaknesses of current theories of biological evolution?

The issue has prompted many scientists and teachers to come out against the bill. They hoped that the Governor would veto it. He didn't. A petition signed by thousands of Tennesseans was presented to the Governor Bill Haslam [Governor petitioned to veto "monkey bill"].

Explaining her opposition to the bill, petition organizer Larisa DeSantis, who teaches in the Department of Earth and Environment at Vanderbilt University, told MSNBC, "What it does is bring the political controversy into the classroom, where there is no scientific controversy," adding, "As a science teacher I would say there is no controversy over evolution or climate change in the scientific literature ... Sure, we argue about the details. But these are core ideas … that are not controversial."

This seems typical of the rhetoric over this bill and a similar one that was passed in Louisiana a few years ago. Evolution defenders seem to be committed to the idea that the way evolution is taught in high schools is not controversial and therefore there is no need to discuss any weaknesses. I doubt that this is true.

I don't know what the standards are in Tennessee but I recently had a chance to look at proposed national standards for teaching evolution as advocated by the National Academies in A Framework for K12 Science Education.

Biological evolution explains both the unity and the diversity of species and provides a unifying principle for the history and diversity of life on Earth. Biological evolution is supported by extensive scientific evidence ranging from the fossil record to genetic relationships among species. Researchers continue to use new and different technologies, including DNA and protein sequence analysis, to test and further their understanding of evolutionary relationships. Evolution, which is continuous and ongoing, occurs when natural selection acts on the genetic variation in a population and changes the distribution of traits in that population gradually over multiple generations. Natural selection can act more rapidly after sudden changes in conditions, which can lead to the extinction of species. Through natural selection, traits that provide an individual with an advantage to best meet environmental challenges and reproduce are the ones most likely to be passed on to the next generation. Over multiple generations, this process can lead to the emergence of new species. Evolution thus explains both the similarities of genetic material across all species and the multitude of species existing in diverse conditions on Earth—its biodiversity—which humans depend on for natural resources and other benefits to maintain themselves.

This is a proposal from the leading scientists in the USA. It's reasonable to assume that something similar is in the curriculum standards for Tennesse. For the sake of argument, let's assume that's true.

Let's assume that a knowledgeable high school teacher in Tennessee decides to teach her students that this definition of evolution is incorrect, or at least incomplete. Let's imagine that she points out several weaknesses, including the fact that analysis of DNA sequences shows little support for the idea that natural selection is responsible for the diversity within and between populations/species. What if she teaches her students that random genetic drift, not natural selection, might be behind most speciation events?

That teacher is posing a direct challenge to the standard curriculum that she is required to teach. Shouldn't she be protected from firing?

Do you see the problem? As scientists we can't proclaim that evolution is taught so well in the public schools that there is no legitimate scientific debate over the fundamentals of evolutionary theory. We can be almost certain that evolution is taught poorly in many schools and there's plenty of opportunity for legitimate criticism in the classroom.

Let's think of another example. Imagine a teacher who is really concerned about what the fossil record shows. He teaches his students that the fossil record does not show the gradual transformation of one species into a new species as the curriculum implies. Instead, new species seem to spring into existence in the blink of an eye as demonstrated by Gould and Eldredge over forty years ago. Furthermore, the Cambrian explosion shows that all animals appeared at once in the fossil record. This is not consistent with evolution.

Should this teacher be fired while the other one is protected? It's very difficult to make a law that distinguishes between the correct exposure of weaknesses in the first example and the incorrect criticism in the second example.

The goal should be to create a curriculum that exposes the students to critical thinking while, at the same time, getting the basics correct. Until that happens, we have no right to say there aren't any weaknesses in the way evolution is taught in high schools in Tennessee.

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