Darwin Day Talk
So the big talk went well yesterday. Around thirty people showed up. If there were any creationists in the audience, they didn't say anything. Here's the Cliff's Notes version of what I said.
I began by showing a few of those cartoons Ken Ham likes so much, in this case drawn from his book Creation Evangelism for the New Millenium. You now the ones I mean. The ones that show evolution as the foundation of a secular worldview that promotes abortion, homosexuality, family breakup and all that other nasty stuff. I then rhetorically asked what kind of scientific theory could possibly provoke a response that irrational.
From here I discussed a few common myths about evolution. Evolution is neither a theory about the origin of the universe, nor about the origin of the Earth, nor about the origin of life. I gave examples from various cable news pundits illustrating each of these fallacies. Likewise, evolution is neither an atheistic theory nor is it a theory of random chance. I pointed out that the claim that humans and lobsters shared a common ancestor does not imply that we should expect to dig up a half-human half-lobster fossil. Finally, I explained why evolution does not say we evolved from apes.
After clearing up what evolution is not, I spent a few moments explaining what evolution is. I identified the hypotheses of common descent and natural selection as the primary shaper of that descent as the core of the theory.
Then I launched into the longest part of the talk, wherein I laid out some of the evidence for common descent and natural selection. The audience consisted primarily of students and I did not want to assume they were familiar with this area. Judging from the comments I got after the talk, this seems to have been the right decision.
I began with the fossil record, and argued that fossils provide three types of evidence for common descent. First, the broad history of life as revealed by the fossil record is perfectly consistent with common descent. No Cambrian rabbits, to use a famous example. Second, creationist protestations notwithstanding, there are droves of transitional forms in the fossil record. Finally, the geographic distribution of fossils supports common descent. For example, armidillos are native to South America, and that is also where you go to find the fossil ancestors of modern armidillos.
Next up was the issue of anatomical homologies. I used the ye olde forelimb example. There's a reason it's a classic. Why do the forelimbs of humans, whales and bats, among others, use the same bones in the same relative positions? This makes no sense from an engineering standpoint, but makes perfect sense if all of these critters evolved from a common ancestor.
Then came embryology. Why do the early developmental stages of very different organisms nonetheless look nearly identical? Why do human embryos form tails and yolk sacs? Why is it that birds possess the genetic information for making teeth when that information is not expressed in modern birds?
Then we talked about vesitigal structures like pelvic bones in whales in snakes. I brought up many others as well. Everyplace else we find pelvic bones they are there for attaching legs to torsoes. If whales and snakes evolved from critters with legs, this is easy to explain. If not, then what are they doing there?
I said a few words about biogeography as well, but I won't belabor that here.
Finally I discussed some of the genetic and molecular evidence for common descent and thisis where things got interesting. I used the example of cytochrome-c. I explained that all organisms possess some form of this protein, but that there is enormous functional redundancy in its structure. In other words, there are many different functional forms of the protein. Human and yeast cytochrome-c differ in over forty precent of the protein, but human cytochrome-c works perfectly well when transplanted into yeast.
How then to explain the fact that human and chimp cytochrome-c is identical? More genearlly, how do we explain the fact that the phylogenetic trees constructed by analyzing cytochrome-c across the animal kingdom perfectly matches the phylogenetic trees constructed by other methods. I argued that this fact alone argues strongly for common descent.
These patterns certainly can't be epxlained funcitonally, after all. And given the sheer variety of functionla cyctochrome-c proteins, we can't explain it as the result of chance either.
At this point an audience member asked how the ID folks explain this fact. I had to confess I didn't know. The only ID proponent I could think of who has addressed this subject was Cornelius Hunter, who did so in his contribution to Dembski's anthology Uncommon Dissent. But his only reply was to hold out the vague hope that there was some functional explanation after all for the patterns. Does anyone know of any other ID reply to this point?
I completed my round-up of the evidence for common descent with a discussion of retroviral scars. For example, the genomes of primates reveal numerous insertions of retroviral DNA. As with the cytochrome-c, the patterns of these insertions matches perfectly with the phylogenetic trees constructed by other means.
Next up was natural selection. I began with Darwin's description of natural selection from The Origin. Then I used Dawkins' “Methinks is like a weasel,” experiment to illustrate how it is possible in principle for natural selection to craft complex structures.
I then provided brief discussions of evolutionary computation, known instances of speciation via artificial selection, field studies of natural selection, laboratory experiments on selection that have shown that new functionalities can evolve, ring species, and artifical life. After this summary I argued that the upshot is that any claim that the adaptations of modern organisms are not the result of natural selection will have to be defended by appeal to specific biological data. There is no sound, armchair argument that can show that natural selection is fundamentally incapable of doing what biologists attribute to it.
I next offered three lines of evidence to show that natural selection really was responsible for crafting the complex systems in nature. I pointed to the fact that many complex systems appear to be cobbled together from parts that were readily available in related organisms. I used the examples of the bee-attracting gizmos of orchids. I also observed that, again, ID protestations notwithstanding, scientists had discovered plausible series of intermediates for a great many complex structures.
Related to this line of evidence are the many “senseless signs of history,” to borrow Gould's phrase, that we find in modern ogranisms. I pointed to the fact that we breathe and swallow through the same tube as an example. This makes perfect sense in the light of evolution (which posits that this system evolved from more primitive systems in ancient lungfish). I pointed to other examples as well, such as the weakness of our lower backs and the backward wiring of our eyes.
The final line of evidence came from the applications of game theory to problems of animal behavior. Mathematical models based on game theory explicitly assume that natural selection is the cause of the behaviors being analyzed. The success of these models is testimony to the correctness of this assumption.
This was the longest section of the talk. I next gave a short biography of Darwin and described what, exactly, his contribution to biology was.
Then came a round-up of various anti-evolution arguments. I treated Behe's claims about irreducible complexity in detail, and also said a few words about the tautology argument and the thermodynamics argument. I chose those three because all of them have been prominent lately, and all of them represent attempts to show that evolution is false while making very little appeal to the actual biological data. I used the following representative statement from the Judge's decision in the big Dover case:
The immune system is the third system to which Professor Behe has applied the definition of irreducible complexity. In Darwin’s Black Box, Professor Behe wrote that not only were there no natural explanations for the immune system at the time, but that natural explanations were impossible regarding its origin. However, Dr. Miller presented peer-reviewed studies refuting Professor Behe’s claim that the immune system was irreducibly complex. Between 1996 and 2002, various studies confirmed each element of the evolutionary hypothesis explaining the origin of the
immune system. In fact, on cross-examination, Professor Behe was questioned concerning his 1996 claim that science would never find an evolutionary explanation for the immune system. He was presented with fifty-eight peer-reviewed publications, nine books, and several immunology textbook chapters about the evolution of the immune system; however, he simply insisted that this was still not sufficient evidence of evolution, and that it was not “good enough.”
Since I was mostly out of time at this point I had to jettison the part where I disucssed that recent Washington Post article about the odious Caroline Crocker. See this post for details on that.
So instead I wrapped it up with Darwin's old “There is grandeur in this view of life” quote, answered questions for another hour and a half, and called it a night. All in all, a successful evening.