Evolution 101

Sunday, September 24, 2006

Icons of Evolution

Today, instead of answering your questions, I’m going to give a review of the DVD “Icons of Evolution,” which was actually produced a couple of years ago, but a friend of mine gave me a copy a while ago and so I finally got a chance to see it. This will be long enough to take up the whole podcast, so I’ll get to your questions next time.

The documentary “Icons of Evolution” is a good representative of the current argument from those who have, in the past, argued against the teaching of evolutionary theory in public schools. Although it was produced three years before the Dover trial, it’s argument amounts to essentially the “Teach the Controversy” approach which so many Evolution deniers have resorted to since that trial.

Without a doubt, it’s an effective way to frame the issue. And the documentary goes right for that from the beginning, by setting some common anti-evolutionary arguments in the context of an educator’s fight to teach “all the facts” about evolution to his students. Those of you from outside America may not be fully aware of how persuasive such an argument actually is- Americans take great pride in their freedom of speech, and the idea that any person should be able to voice their opinions on a subject, no matter what they are. They strongly believe in the concept of a marketplace of ideas, in which all points of view are, if not equally valid, at least given equal time. It’s this same mentality that, in my home city of Cincinnati, resulted in the display of a cross on Fountain Square at Christmas time, sponsored by the Ku Klux Klan. And I think, personally, that this is a mentality which should be supported- after all, what is the value of freedom if some voices are being silenced?

But this issue is not about silencing the voices of evolution deniers. There is no law that explicitly says that creationism cannot be taught in public schools- although the documentary tries its best to imply it. The educator in question whose struggle is the framing device for the documentary is Roger DeHart, who taught Biology and Earth Science at Burlington-Edison High School in Burlington, Washington. He got in trouble because, as the documentary says, he cared so much about his students that he wanted to teach them the truth about evolution. But Roger DeHart is no John Scopes. The documentary pushes very hard to cast him as the mirror image of the Tennessee teacher who was taken to trial for teaching evolutionary theory in the face of a law specifically prohibiting it. To quote from that law, the Butler Act: “that it shall be unlawful for any teacher in any of the Universities, Normals and all other public schools of the State which are supported in whole or in part by the public school funds of the State, to teach any theory that denies the story of the Divine Creation of man as taught in the Bible, and to teach instead that man has descended from a lower order of animals.” I’m sure you can see that for the argument to be made that Roger DeHart is the modern-day mirror image of John Scopes is exactly what the evolution denial position does not want to admit. You see, this law was written with an explicit Christian bias, against which the teaching of science was an infraction. But if DeHart is mirroring John Scopes, then it follows that he is against the teaching of science, and instead seeks to teach his explicit Christian bias. Of course, this would never be admitted to by either Mr. DeHart or the evolution denial groups which have sponsored this documentary. And rightly so, because I don’t think DeHart is a modern juxtaposition of John Scopes in the slightest. DeHart was not charged with any crime. He was not taken to trial. He was, however, criticized by his community for teaching a deviation of the prescribed curriculum which was recognized at that time, and has been recognized officially and legally after the fact in Dover, Pennsylvania, as a specifically religious deviation. In fact, DeHart was examined as part of the Dover proceedings, and admitted that a significant part of his evolution lesson plan was derived from the book, “Of Pandas and People,” which was found to be a clear piece of educational propaganda of the evolution denial movement, and part of the evidence which sealed the decision at Dover against evolution denial. As a matter of fact, Mr. DeHart has admitted to evolution denial, belief in a young earth of less than 100,000 years old, and instead claims that a better explanation of the facts comes from the belief in a designer. That’s right- Intelligent Design raises its head.

Suddenly this issue seems a lot less like a lone science teacher wanting to take a stand to teach the honest truth about his subject, and more like someone with an ideological axe to grind. I don’t intend here to use ad hominem criticisms of Mr. DeHart or anyone else who is involved in this issue, but it strikes me as telling that the central player in this drama just happens to be teaching a curriculum that just happens to be aligned closer to his theological position than to accepted science. And ultimately his community found that telling as well- and criticized him for preaching his theological beliefs as science in the classroom to the point where he resigned (was not fired, but resigned) from his position and eventually ended up moving to California and teaching at Oaks Christian High School, where presumably, his desire to teach Intelligent Design is not a problem.

After setting up a sympathetic context to get the audience in the mindset to favor a “teach the controversy” approach, the documentary moves on to the meat of the issue, which is essentially attempting to trash evolutionary theory. The arguments that follow are from a book by Jonathan Wells, not coincidentally titled “Icons of Evolution.” Before I address those arguments, I think something needs to be said about Wells also. Again, I don’t want to engage in ad hominem criticisms, but it can be informative to know the biases of those to whom you’re listening. For example, you should know that my sources of bias are: I am a molecular biologist, taught that evolution is a fact of reality. I’m also an atheist, and so I have no compelling theological reason to reject evolutionary theory (or any other scientific theory, for that matter, but evolution is the subject here). So that’s my bias, and you have to, as the listener, take that for what it’s worth. I don’t believe that either my scientific training nor my lack of god-belief give me a particular axe to grind in regards to evolutionary theory- in fact, I’ve said before that even when I was a Christian and before I entered college, I didn’t think twice about accepting evolutionary theory. But I think it’s significant when a person not only has potential sources of bias, but admits them as responsible for his positions outright. Jonathan Wells is a theist, and a member of the Unification Church. For those of you that aren’t familiar with this denomination, they’re frequently called the “Moonies,” because they believe that their leader, Sun Myung Moon, is the Second Coming of Jesus Christ, called by the Moonies themselves as “Father.” From Wells’ own words: At the end of the Washington Monument rally in September, 1976, I was admitted to the second entering class at Unification Theological Seminary. During the next two years, I took a long prayer walk every evening. I asked God what He wanted me to do with my life, and the answer came not only through my prayers, but also through Father's many talks to us, and through my studies. Father encouraged us to set our sights high and accomplish great things. He also spoke out against the evils in the world; among them, he frequently criticized Darwin's theory that living things originated without God's purposeful, creative activity. My studies included modern theologians who took Darwinism for granted and thus saw no room for God's involvement in nature or history; in the process, they re- interpreted the fall, the incarnation, and even God as products of human imagination. Father's words, my studies, and my prayers convinced me that I should devote my life to destroying Darwinism, just as many of my fellow Unificationists had already devoted their lives to destroying Marxism. When Father chose me (along with about a dozen other seminary graduates) to enter a Ph.D. program in 1978, I welcomed the opportunity to prepare myself for battle.”

Thus, Jonathan Wells sought out and earned a Ph.D. in molecular and cell biology at Berkeley specifically to earn the credentials he felt were necessary to attack evolutionary theory from “within.” He did, in fact, publish two peer-reviewed papers as a graduate student on the subject of frog embryo development, but nothing else. After graduating, he was placed briefly in an unpaid postdoc position by his mentor Philip Johnson of the Discovery Institute, and then moved directly into a position there. He published the book “Icons of Evolution” in 2000. And as I mentioned, it is the arguments from this book which form the bulk of the documentary. I’ll go through them now, and explain what mistakes are made in the presentation of these arguments, and what the scientific evidence actually shows.

The arguments against evolutionary theory in the documentary, as in the book, attempt to undermine certain evidences that support evolutionary theory which are considered key, or defining evidences. Wells argues that these evidences are treated as icons, hence the title of the documentary and book. The implication is that if these icons can be undermined in some way, evolutionary theory as a whole is called into question. Even if this task was achieved, of course, this wouldn’t threaten evolutionary theory in the slightest- I’ve spoken at length about the molecular evidence for evolution, which is not considered by this documentary. Given just the molecular evidence, a substantial case could be made for evolutionary theory by itself.
The first icon is Haeckel’s embryos. I won’t go into detail about this argument, because I’ve already debunked it months ago, in podcast 107. If you remember that episode, you recall that Haeckel had advanced the hypothesis that “ontogeny recapitulates phylogeny.” Evolutionary biologists have since then rejected that hypothesis, although it is worth nothing that ontogeny does organize according to phylogeny- human embryos do have “gill slits” as Haeckel drew, it’s just that they don’t turn into actual gills. Incidentally, none of my biology textbooks from college have this image in them, although they did dedicate entire sections to explaining evolution. I find it somewhat odd that these embryo drawings could be honestly considered to be an “icon” of evolution when they didn’t even factor into my biological or evolutionary education in the slightest. In fact, the first that I had ever heard about them was through being exposed to attacks on evolution from people such as Jonathan Wells. It seems that the science has long since moved past the need for Haeckel’s embryos, but the evolution deniers have not.

The second icon is Darwin’s finches. As I’ve mentioned in a previous podcast, Charles Darwin visited the Galapagos islands as part of his voyage on the H.M.S. Beagle, and although he wasn’t particularly interested in the different finch species while he was there, they did influence the development of his theory of natural selection when he had returned to England. Of particular note to Darwin was the size of the beaks of the various species, and how they correlated to the availability and size of seeds as a food source. According to Darwin, these species of finch were evidence for adaptive radiation, meaning that one finch species had been introduced to the islands at some point in the past, and the forces of natural selection among the different islands had caused speciation from that original population. What’s curious to me is that, in the documentary, no criticism is directly made against the finches themselves, the fact that their beak size changes in response to environmental changes, or even that this process can be observed. What happens is that Wells makes the argument that these changes cannot be extrapolated into actual speciation- instead, he says, it represents a kind of cyclic variation within the different populations of finches. Specifically, that since beak size changes in a way which correlates to changes in the environment, a population with a larger beak during drought reverts back to a population with a smaller beak during good rainfall. In other words, he’s making the argument that Darwin’s finches represent microevolution, and not macroevolution. Again, this is a subject that I’ve covered before, in podcast 102. There is no mechanistic difference between micro and macroevolution, just differences in scale. Beside the fact that there is a clearly observed mechanism for physiological change in the finches, morphological comparisons demonstrate that macroevolution has indeed occurred.

The documentary then moves on to the fruit fly. Fruit flies have long been used in studies of genetics because they are small, grow very fast, reproduce in large numbers, and have a small number of chromosomes. Also, the techniques for manipulating fruit fly genes have been around for a long time and are well established, so there’s a pragmatic aspect to using them as a model. In addition, they’re not vertebrates, so there’s not as much bureaucratic red tape associated with growing them in a laboratory compared to, say, mice and rats. In the documentary, the argument is made that although genetic change can be induced in the laboratory, the phenotypic results of these changes are not the kind which confer any kind of selective advantage. For example, fruit flies can be induced to grow an extra set of wings. In the documentary, these four-winged flies are shown buzzing around ineffectively, hampered by the extra, non-functional wings, and unable to survive normally, without being in the laboratory. The argument is then made that since this mutation actually makes the fruit fly’s life more difficult, then it is not a selective advantage and is not evidence for evolution. This kind of argument is typically referred to as a “straw man,” because it addresses a position not claimed by its opponent, which is roughly equivalent to picking a fight with someone, but instead of fighting them directly, building a straw dummy of that person, and then beating up the straw man. No geneticist has ever claimed to my knowledge that the mutations induced in the fruit fly in a laboratory setting have ever been an example of a speciation. That’s not why fruit flies are important, and this really troubles me about the documentary that it could take such an incorrect view of a basic model organism like the fruit fly. Fruit fly mutations aren’t important in and of themselves as an example of speciation- they’re nothing more than phenotypic markers, visible signals that show when a gene has been altered in some way. What the fruit fly has contributed is the basic understanding of genetics- by observing the frequency and heritability of the mutations that are induced, geneticists have been able to learn a great deal about how genes function in all organisms. I don’t think any geneticist actually set out to “evolve” a new species from fruit flies. That might be interesting, but not nearly as interesting as learning how genes function within organisms. So this “icon” really doesn’t support the overall argument of the documentary. Of course a four-winged fruit fly would be selected against in the wild- this explains why fruit flies have not evolved with four wings.

The documentary then moves on to the concept of antibiotic resistance in bacteria. This “icon” is kind of a mix between Darwin’s finches and the fruit fly in concept. Just as with the finches, the argument is made that selective changes revert back to a preexisting population genotype, and just as with the fruit flies, these changes are charged with not being examples of speciation. And as you would expect, the rebuttal to both these points remains the same as before, so I won’t belabor it. But briefly, the selection of bacteria by environmental condition (presence or absence of an antibiotic) is absolutely the mechanism of change that is posited by evolutionary theory- so I’m not sure what the problem is here. The fact that the bacteria lose antibiotic resistance when the antibiotic is removed from their environment isn’t an argument against evolution- it completely supports it. When any selective pressure is removed from a population, evolution is going to favor those members of the population which can reproduce best in the absence of that pressure. And when antibiotics are concerned, those bacteria which are not resistant reproduce much better, because antibiotic resistance comes at a metabolic price. And no microbiologist has ever claimed to be interested in creating new species of bacteria simply by adding or removing an antibiotic. So again, this is a straw man.

The next attack is on the concept of homology as evidence for common descent. Not homology per se, it’s pretty tough to refute the actual homology that exists between different organisms, even for a documentary as obtuse as this one. Instead, they make the argument that structures that share homology between different organisms should also share a genetic basis for that homology, if common descent is correct. They then look at the fruit fly again, and compare it to the wasp. The body segments, they say, are considered to be homologous, but instead of being controlled by the same gene, they are controlled by different genes. Thus, biologists cannot explain homologous structures that are caused by different genes. First of all, yes biologist can explain them- it’s called convergent evolution. This is the idea that selective forces experienced by different organisms are similar enough that, in certain situations, different organisms can “come up with” the same evolutionary solution to a selective problem. For example, the wings of birds and bats are an example of convergent evolution- bats did not evolve from birds, and in fact, if you go back to the nearest shared common ancestor between bats and birds, you find no wings at all. So both birds and bats evolved wings independently, as separate but very similar solutions to the problem of how to achieve powered flight. Going back to the fruit fly and wasp- this really isn’t an example of convergent evolution in my mind, but it’s awfully hard to tell, because the documentary doesn’t even give the name of the gene that supposedly is different between the two species. So there’s no way to verify if what they’re claiming is true. What I do know is that there have been several mutant genes identified in wasps which affect the development of body segmentation which are different from the mutations characterized in fruit flies, but this is no problem either, since fruit flies diverged from wasps over 200 million years ago, and we would expect some divergent evolution during that time. So once again, a straw man.

The final so-called “icon” of evolution is the “tree of life”, which is a metaphorical concept used by evolution to explain the relationships between all organisms. The argument that is used in the documentary is one that is based on a fundamental misconception of evolution that is actually pretty common among evolution deniers. The tree of life is not some kind of teleological necessity- in other words, the relationships between different organisms are not necessarily a reflection of the progression of time. That is, as time marches on, the number of species in existence does not necessarily increase. In fact, if anything, the number of species in total existence has decreased- millions upon millions of species have gone extinct over time, and species are constantly going extinct even today. So the idea that the tree of life is one which is small on one end and large on the other isn’t really an evolutionary necessity. Certainly, at some point in the history of life, the number of species was very very small. But once life was able to diversify, it did so without question, and the rest of biological history has been a refinement of that diversity, as different species compete for resources. The documentary focuses on the so-called Cambrian “explosion,” as a contradiction of its own assumptions about evolutionary history. Yes, you guessed it, another straw man. The argument says that since there were so many species in existence during the Cambrian period, and since this happened so quickly, it contradicts evolutionary theory. Well, first of all the Cambrian explosion did not happen overnight. Nor did it happen over seven days. It occurred over a range of time between 490 and 550 million years ago. And there are many explanations for the wide diversity of animal groups found within Cambrian rock, all of which are consistent with evolutionary theory. One explanation is that, it was only during the Cambrian period that organisms had evolved which contained body parts that lent themselves well to fossilization. Imagine, for example, if newspapers started to be printed on plastic sheets, instead of paper sheets. The plastic newspapers would be thrown away at about the same rate as the paper newspapers, but they wouldn’t degrade as readily. Thousands of years in the future, I could imagine a team of archaeologists unearthing a garbage dump from the early 21st century and wondering how strange it was that people suddenly started reading newspapers after the turn of the millennium. Another possibility is that environmental oxygen levels had not yet become high enough to promote the evolution of animals into any degree of complexity or diversity. Another explanation is that severe environmental and weather changes on the Earth at that time affected the chemistry of the oceans, promoting wide diversity and evolution of the organisms there. And a recent explanation involves the genes that have been characterized by Evo-Devo (which I’ve mentioned before) such as the Hox genes, which may represent the minimum requirement genetically for the development of wide diversity. It’s possible that these genes or prototype versions of these genes had developed by the Cambrian period allowing for a genetic basis of the kind of diversity seen in Cambrian fossils today.

The documentary is capped off again by an appeal to the audience’s sense of fairness, and an appeal to do the best thing for our students by teaching them the “full story” of evolution. Again, this is a strategy which has a lot of sympathy with the average person, especially here in America, but it just doesn’t hold up. I have shown here and others have shown elsewhere and much more detailed than myself that the so-called “rest of the story” that the evolution deniers want to be taught does not represent an accurate scientific argument. Are we really doing our children any favors by teaching them material in the science classroom that is demonstrably not science? Should we teach astrology to our children, to give them the “full story” about astronomy? Should we teach alchemy, to give the “full story” about chemistry? The power of science lies not just in the information that it adds to our body of knowledge, but in the information that it removes from it. Make no mistake, evolutionary theory is a scientific theory, like it or not. The only controversy that needs to be taught is the public controversy that should serve as a warning to everyone that science can and will be threatened by those who place ideology above reality.


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