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Evolution: Teaching the Controversy

Today in the United States there are some groups calling for teaching creationism or intelligent design in public high school Biology classes. Proponents of these ideas sometimes argue that we should “teach the controversy”: the idea being that evolution is a controversial concept and we should teach both sides of the issue. Some suggest this may even help students get a deeper understanding of the material and the scientific method. Some also say that failing to do this is simply indoctrination. Those arguments may sound reasonable, and, certainly, it's hard to argue with the idea that reinforcing the scientific method is a bad idea, since it is the core of science. I believe the above argument is actually misguided, but I don't think the reasons are necessarily obvious. Below I will try to make those reasons clear in a way that I hope will speak to you whether or not you are inclined to agree with me at the beginning. I will focus mostly on the idea of intelligent design, because it seems to be more popular lately. Because of their similarities, most of what I will say applies equally well to creationism. I should also say that when I talk about “evolution” I mean the modern biological understanding of how the many complex species that exist today (including humans) arose from a few simple organisms by the process of natural selection. Let me also add the disclaimer that I am a physicist, not a biologist, so I'll do my best with my understanding of Biology, though most of what I have to say doesn't have much to do with Biology specifically.

What Should be Taught in Science Class?

In any class, we try to teach material that people with a lot of knowledge of the subject widely agree is likely to be close to correct and agree is important to either understanding the field or to using it for practical purposes. This fairly general statement should apply to History, English, Mathematics, or Science. In History, for example, we rely on historians to determine which ideas about History are well founded and for guidance about what facts about the History of a particular time and place we should use classroom time to discuss. There may be new ideas about a certain period that are not yet widely agreed upon, and we generally don't include them. There may also be “fringe” theories about History, which may even be held by a minority of researchers, say an idea about a very early civilization in the city of Atlantis, and we don't include those either. In both cases, the justification is usually that the people who know about history, who are familiar with what is known and what research has been done, don't agree that those ideas are important and well founded enough to be included. We rely on the consensus of experts. The idea behind this is not that the rest of us aren't smart enough to make these decisions, only that we don't have the specialized knowledge of the subject area. A related question you might ask is who we should consider an “expert”. A good standard would be to listen to people who have made contributions to the field that are widely recognized as being useful. In science, this is particularly easy, since whether ideas are useful or not is decided by results in the laboratory for everyone to see. So the people we can consider “experts” are the ones that have in the past allowed us to predict the behavior of the physical world and, perhaps, use that behavior to our advantage through technology.

Sometimes, when discussing ideas like creationism or intelligent design people talk about how popular these ideas may or may not be. The question, then, is whether we should decide what to teach in a class based on the popularity of the ideas among the general public. A great many people think that no one knew the Earth was round until Christopher Columbus sailed to the Americas. Should we teach that in History class, even though in the 3rd century B.C. Eratosthenes not only already knew this but already measured the circumference of the Earth? Should the answers we teach to math problems be determined by popular opinion? In the case of science, a good example is the following question: “What causes the seasons?”. The majority even of college educated people seem to believe that it's because the earth is further from the sun during the winter than it is during the summer1. If we were deciding what to teach in science class based on what belief most people in the general public hold, that's the answer we'd be teaching in science class and not the correct explanation. One can easily imagine more objectionable examples. In a community that is home to a significant number of Holocaust deniers, should the History class teach that the Holocaust did not happen? The purpose of education, of course, is to make people more knowledgeable by passing on the things that others have worked long and hard to figure out, not to pass on common misconceptions. So, we can't choose what to teach based on popularity among the general public; we have to look at the consensus among those people who have studied long and hard to become experts on the subject in question. That is the way that we educate and produce people who know more than those who came before them.

Is there a Controversy?

The main idea on which the “teaching the controversy” argument is based on is that there is a controversy. While it's true that there is disagreement in the general public about whether the theory of evolution is correct, we've just discussed why what we teach in science class is not, and should not be, based on popular opinion. Proponents of “teaching the controversy” often attempt to claim there is a controversy in the scientific community about whether the idea of evolution is correct; however, this is simply false. Part of understanding this depends on understanding the way in which science works. Scientific study is an ongoing process where we constantly do new research to refine our understanding of the Universe. No scientific theory is ever “done”. An existing theory is usually approximately correct, but new evidence allows us to see ways in which it is not quite right, and we must make revisions to the theory that reflect the new things we've learned about nature. This means that scientists will often debate and even revise details of a theory even if there's agreement that the theory is generally correct. For example, in my field, Physics, it is widely recognized that our current theory of gravity is incomplete, and there is a lot of debate as to what the correct theory is. But these are, in essence, the details of the theory, and there is no controversy about the theory of gravity as it is taught at the high school level. The situation with evolution is the same. Our scientific understanding of the details of evolution is still improving, but scientists agree that the basic idea of evolution is correct and, furthermore, that it is the central idea to understanding Biology.

People wishing to portray a controversy will try to pretend the debates over the details of evolution are debates over evolution itself, even going so far as to quote scientists out of context to make it appear that they are disputing evolution when they actually are not.2 You need only read the complete remarks of those scientists, or look at statements by the Union of Concerned Scientists or the National Academy of Sciences or various Nobel prize winners, or just look at the scientific literature itself to see there is no controversy among scientists about the fact that evolution is correct or about the fact that it is very important to understanding Biology as a whole3. Does that mean there's not a single person in the world with a Ph.D. in a scientific discipline who disagrees with the idea of evolution? Of course not. If you look hard enough, you can find people with Ph.D.s who dispute just about any scientific theory, from our understanding of gravity to evolution. If we used that as our standard of controversy, then practically every scientific theory would be considered controversial. But if you ask what is the scientific consensus and do the vast majority of scientists agree that evolution is a correct description of the way nature works the answer is yes, so it's not controversial in any reasonable sense.

Intelligent Design is Not Even a Scientific Hypothesis

This is a topic that probably deserves a separate discussion, but I will try to talk about it briefly here, since it relates to what I'm going to say next. You may find further discussion of these and similar ideas in the Intelligent Design Theory node. Let me start with two questions: There are many subjects that aren't taught regularly in high school (like linguistics or philosophy). Why does everyone teach Science? Why do people put so much stock in what scientists tell us about the world? To find the answer to both these questions I think you only have to look in front of you right now, at your computer. People put stock in Science and consider it important because science works. Our scientific understanding of the world allows us to create technology to help us stay fed, safe, and warm, to help us communicate and travel, and a great many other things. Science allows this because it allows us to think of what we want to accomplish and understand how a device must work in order to accomplish that end.

In order to be useful in this way, a scientific idea, a hypothesis or theory, has to actually make predictions, and we must be able to test those predictions by making observations that may possibly show our hypothesis to be incorrect. So, we can say that a scientific hypothesis must be predictive, and falsifiable. This is the core of what defines science. The theory of gravity, for example, predicts that if you drop two objects of different weights in a vacuum (a region where the air has been removed) they will fall at the same rate. You can go and do that measurement in a laboratory. There are other scientific ideas that you can't necessarily test in a laboratory, but you can still make observations, out in space or in the geological record, to see whether or not their predictions are shown to be false. Evolution predicts that over time we should see the types of life becoming more varied and complex. We should see one species divide into two different species if the two groups are in separate places with separate environments over a period of generations. These are things we see evidence for in the fossil record and by analyzing genetic similarities between different species. If, for example, scientists had looked at the fossil record and found that complex organisms like humans had existed throughout history, then evolution as an explanation for the origin of man and the diversity between different species would have been disproved. Thus, evolution is a scientific theory with tested predictions. I'd also like to stress that ideas about genetics and evolution are useful, in the way I outlined earlier. They help us deal with genetic disorders and understand phenomena like antibiotic resistance as well as helping us understand ecology to better manage our natural resources.

The core claim of intelligent design is that the diversity of species, and particularly the origin of man, cannot be explained by natural causes alone, and, in fact, they show signs that they were designed by some “intelligence”. The question, then, is what predictions does this theory make and what observations could you make to try to disprove them? In other words, how is this idea useful in the way that science is supposed to be useful, to predict things and help us make technological advances? Saying that a certain phenomenon cannot be explained by natural causes is not such a prediction. It might be a statement about the limitations of scientists, that they don't know everything and aren't smart enough to figure out every problem immediately, but it's not a statement about nature that you can go out and test. It does not say, “Go out and look in nature and you will find this...” As I suggested, you can also see this by the fact that it's not useful in the way I described; this could never help you to develop a new piece of technology and predict how it will behave or devise a new medical treatment. A student is in Biology class to learn about the anatomy of different animals, genetics, the structure of cells, etc. so that he or she will have the background to possibly go on to be a medical doctor , develop new medicines, understand the way proteins fold, develop more productive crops, or any number of other things. Ask yourself how this idea of intelligent design could possibly be useful in figuring out the details of how to accomplish these things. It can not.

Science is the process of working to understand things we don't yet have an explanation for; if we simply stopped and said “this must be the work of some higher intelligence” every time we found something we could not yet understand,science would not exist and neither would all the technological advances it has allowed. People did not, for example, immediately understand electricity. Electrostatic charges, commonly called static electricity, can cause two objects to be attracted to one another. That phenomenon has been seen probably throughout history, but it wasn't really understood until the last few hundred years. Seeing two objects attracted to one another with no apparent explanation, people could have thought it was caused by ghosts, because clearly inanimate objects don't normally just move on their own. The lack of scientific explanation at that time would not make the “ghosts” hypothesis true, and the ghosts hypothesis would in fact be completely unscientific, because, again, it could not possibly be proved false. Of course, further experiments showed that the attraction is caused by electric charges, and thankfully scientists of the time kept looking for causes with the scientific method, rather than resorting to an “intelligent design” type explanation, allowing the development of technologies like the ones that allow you to be reading this.

Now intelligent design also claims that organisms will look as though they were designed by some intelligence, but the question we must ask is how could I make an observation that objectively proves something is not designed by an “intelligence”? But, of course, the question of whether something seems like it was designed by an intelligence is subjective, it doesn't make any clear prediction that would be disproved by an observation. You can certainly ask whether something is designed by humans, because in that case you can see if it contains compounds that don't occur in nature. You could make that determination objectively (though maybe not with certainty), because there are concrete questions that can be answered by observation. But if you just ask whether something was designed by some unspecified “intelligence”, whose properties you can't measure or observe directly, then there's no way to test whether that intelligence is responsible. Some proponents of intelligent design have suggested that if you can find organs in a creature that are irreducibly complex, meaning that they will become completely useless if any part doesn't function properly, then this is evidence of a designer. The first point is that again this is just saying something exists that we can't explain, which is not a prediction about nature itself. The point is that the existence of an irreducibly complex organ might disprove the idea that the organ could have been the result of evolution4, but it doesn't tell you that an intelligence is responsible. It only tells you that there must be some alternative explanation. The second point is that no such irreducibly complex organ has been found. People have claimed various organs were irreducibly complex, but so far it's been shown that each one could have come about through the process of evolution.

For these reasons, intelligent design is not a scientific hypothesis. It doesn't make concrete predictions that could be objectively disproved by observations, so it could never be useful in the way that Science is designed to be useful. I want to be clear, though, that I am not saying that Science can prove there is no designer. Note that I've specifically said that it's an idea that cannot be disproved using the scientific method. Whether a supernatural intelligence is responsible for what happens in the world is beyond the sort of questions that Science can answer, because it does not fit in with the scientific method, so Science has nothing to say on the matter one way or the other. That sort of question is a philosophical question, specifically it would fall under the area of metaphysics, and it would be entirely appropriate to address it in a Philosophy class, but it has absolutely no place in a Biology class.

Teaching Scientific Controversies and the Scientific Method

The scientific method is what defines Science, so it is perhaps the most important thing for students to take away from a science class. Would teaching students that there's a controversy over evolution help them learn about the scientific method? It's actually standard practice to talk in a science class about older theories that were at some point popular but were disproved using the scientific method. For example, in Physics you can talk about Aristotle's idea that an object must always be pushed in order to keep moving, or you might talk about the geocentric model of the solar system5, and in Biology class it is actually quite usual to talk about the discredited idea of Lamarckian evolution, which was defeated by Darwinian evolution. These are useful teaching tools for several reasons: The two theories in question are both scientific theories, meaning they both make testable predictions. The differences between the two theories are simple enough that they can be explained clearly and completely enough for the students to understand how each does and does not fit the real world. And, finally, it's useful that the disagreement is in the past, so that students and teachers can discuss it objectively without their personal or political feelings interfering with their ability to apply the scientific method, and the resolution can be more clearly understood with the benefit of hindsight.

If you now think about the evolution “controversy”, you can see why it doesn't really fit in. First, intelligent design does not make testable predictions, as we discussed above, so it can't be used with the scientific method at all. It's not a scientific hypothesis, and suggesting to students that it is would probably actually confuse their understanding of the scientific method. Second, modern ideas about evolution have advanced a lot since Darwin, and truly understanding them takes an in-depth understanding of genetics and biochemistry, the details of the anatomy of many animals, and possibly even geology and palaeontology (when you start talking about the fossil record). Students are just learning the basics of these things (at best) when they are taught about evolution, so they are given a basic idea about the theory of evolution. At that level they just don't have enough background to really give a complete analysis of possible problems with Darwinian evolution. That's why the Darwinian versus Lamarckian evolution is so useful to discuss, because the difference between the ideas as they existed at that time is simple enough to discuss with students just learning about Biology. Finally, I doubt I need to point out that while there may not be a controversy over evolution among scientists, there is a controversy among the general public in some places that many people feel very strongly about.

It's not really standard practice, as far as I am aware, to discuss pseudoscience (ideas that may look like or claim to be scientific but actually are not) in Science classes. I can accept the idea that perhaps it would be useful for students to learn about examples of pseudoscience and how to recognize them. In principle then, a discussion of intelligent design could be useful as an example of something that might seem like a scientific hypothesis, but actually isn't. In practice, I think it's probably quite clear to everyone that making that statement in science class is far too likely to cause political controversy and take the attention away from where it ought to be: on teaching children science. If we were going to talk about pseudoscientific theories in the classroom, it would again be better to discuss historical examples that are simple enough for students just learning the subject and can be approached objectively without political ideology getting in the way of understanding the Science.

Suppose you ignore what I said above and assume that intelligent design is a scientific hypothesis that has just not gained popularity among scientists. In that case, shouldn't we teach it in science class? In the first section, I indicated that what we normally do in science class, as in any other class, is teach the ideas that are widely agreed on among experts, so the answer then to whether we should teach intelligent design would still be no. Besides the fact that the students are just learning the basics and don't have the expertise to figure out whether the new theory is good, there's also the simple fact that there's a very limited amount of class time, and it doesn't make sense to spend it teaching things that we're not very certain are correct (at least not at the basic, high school level). It's even more interesting to note that there are many new scientific ideas born every day, and some of those take a long time to gain popularity among the experts. Why aren't the people who came up with those hypotheses pushing to have them taught in science class? Well, the reason is that the people who have the expertise to figure out whether those theories are correct, the resources to make the observations to test them, and can then actually use them in research are practicing scientists, not school children. That's why when someone comes up with a new scientific idea, they publish it in a peer-reviewed scientific journal, talk about it at scientific conferences, or if nothing else they write and publish books. High school students generally aren't able to make direct use of a new scientific hypothesis, and they aren't knowledgeable enough in the details to really be skeptical and tell a good new idea from a bad one. However, one reason for someone to go directly to high schools with his idea is if he can't make a case that convinces people who really know about the field, so he tries to indoctrinate students before they have enough knowledge to critically approach the idea and see its flaws. I have no doubt that many people in favor of teaching intelligent design have only honest motives in mind, but my point is that if you only have honest motives you must admit that high school is not a normal or useful place to seek acceptance for a new scientific idea.


After examining the different aspects of the idea of “teaching the controversy”, I hope you will agree with me on the following points: There is no controversy among the community of professional biologists over whether evolution is correct. To teach a hypothesis without widespread acceptance among experts in a high school science class would not be the normal way of doing things, and it would not really be useful. Intelligent design is not a scientific idea at all, so it does not belong in science class, and teaching it as though it were a scientific idea will only serve to confuse students about the scientific method. If we want students to learn more about the scientific method, there are much better historical examples of actual scientific controversies or of pseudoscientific ideas that would be much more helpful to consider in the classroom and would not run the risk of putting the focus on politics instead of teaching Science. After all these considerations it becomes clear that the “theory of intelligent design” has no place in a high school Biology classroom. I haven't addressed the idea of separation of church and state, which may apply to public schools, at all here, only what is useful in a science classroom, so what I've written should even apply to Biology classes in private school that may teach a certain religion as part of the curriculum. The question of whether there is some supernatural intelligence at work in the Universe is an interesting one that would make a good part of a class on Religion or Philosophy, but whatever your religious of philosophical views it is clear that it's a consideration that has no place in science class.

  1. I base this remark off of the results of a survey given in the documentaryA Private Universe: Mind of Our Own”. I'm not certain if a large and scientific survey on this specific issue has been done, but the result I mention is plausible, given the results of similar surveys.
  2. See http://www.nasonline.org/NEWS_letter_president_03042005_BA_evolution or http://www.talkorigins.org/faqs/quotes/mine/project.html.
  3. As I said, you can look at basically any statement by the groups I've mentioned or search any major scientific publication and see fairly immediately that there is very widespread agreement on the idea of evolution, but it's not as easy to come up with one concise source to show this fact. I can offer the following three links as a beginning: http://www.geocities.com/lclane2/teachingthecontroversy.html, http://www.talkorigins.org/faqs/edwards-v-aguillard/amicus1.html, http://www.talkorigins.org/faqs/steve/.
  4. This is actually debatable, because an organ could come about by evolution in a form that has many extra parts, so that it could function without some of them, then natural selection could lead to a process where the structure simplifies over time until it has just the minimum complexity needed to work. Extra parts generally mean more things to break or get infected and more required nutrition, so they are generally selected against, though not always very strongly. At the end of this process the organ would look irreducibly complex, even though it was not that way when it originally evolved.
  5. The geocentric model of the Universe was, of course, backed by the Catholic church on religious grounds, but the heliocentric model won out eventually, because it was the one that agreed with the facts. Again, had people allowed philosophical or religious ideas to interfere with the proper functioning of Science then we would not even understand our own solar system, let alone what we now understand about the rest of the Universe. Note also that the vast majority of catholics and other Christians now accept the idea of a heliocentric solar system and do not see it as conflicting with their religious beliefs.

This node was inspired by a forum I attended recently on “Religion and the Public Schools” in which one of the topics was the teaching of intelligent design in public schools.

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