On Friday night of October 21, a debate titled, "Is Darwin's theory flourishing or floundering?" was held open for students and the public. It was hosted at St. Edward's University and presented by Hill Country Institute, Christ Church, and Associate Professor of Philosophy at St. Edward's University Dr. Stephen Dilley, Ph.D. The debate centered around whether all of life descended from one common ancestor or not.

As a biology major who is taking both Evolution and a philosophy class titled "God & Science," I attended the debate for both intrigue and because I had to. In fact, Dr. Dilley is teaching my "God & Science" class which discusses the relationship (if there is one) between religion and science and particularly centers around the discourse between evolutionary theory and creationism. As a senior science major taking a philosophy class that challenges the basis of evolutionary theory, I found myself in the privileged position of being able to view the debate from both lenses. Thus, I shall discuss the structure, content, and my impression of the debate in the following sentences.

Structure

The debate gave arguments for both pro- and anti- common descent. Dr. Joel Velasco from Texas Tech University defended common descent and Dr. Paul Nelson from the Discovery Institute challenged it. Dr. Velasco received his Ph.D. in Philosophy of Biology in 2008 at the University of Wisconsin-Madison. Dr. Nelson received his Ph.D. in Philosophy of Biology and Evolutionary Theory from the University of Chicago in 1998. They began with an introduction to their respective arguments, followed by their main arguments, a rebuttal, and Q&A. For purposes of this article, I will not discuss the Q&A portion.

Content

Opening remarks

Dr. Velasco argued that all carnivores, mammals, snakes, plants, eukaryotes, and everything else is related. He argued that all life is genealogically related by common descent.

Dr. Nelson asserted that there are four main opinions on the tree of life: design, no design, one tree, or multiple trees. He argued for the multiple trees of life hypothesis by contending that in the recent last decade, scientists such as microbiologist Carl Woese and biochemist Ford Doolittle found that there can be no single common ancestor since we find organisms outside the domain of the tree of life.

Arguments

Dr. Velasco argued that when we look back at history, over and over again, we find support for common descent because it is, has been, and always will be very well supported by research. We find this data exhibited in the distribution of life on the planet, in the distribution of traits within life, and where fossils are and what they look like. He contended that descent explains these through comparative anatomy, biogeography, and fossil records. In comparative anatomy, we find homologies between species. Velasco used the famous example of the shared radius, ulna, and wrist structures found in human, whale, bat, and frog bones. Velasco argued that all of these species have this comparative anatomy because they all descended from ancestors that had structures just like that. His biogeography argument claimed that all life came from organisms from somewhere else. He illustrated this through the example of the cactus. The cactus is native to the Americas and is not in Africa, Asia, or Europe even though there are desserts there. He claimed that the reason that there are no cacti there is because they descended from a common ancestor which was native to the Americas and did not spread or arise elsewhere because they cannot travel. Velasco also contended that transitional fossils and vestigial structures further attests to the fact that species are related because they share a common ancestor. Lastly, Velasco gave the example of humans having one less chromosome than chimps and instead having the fusion of two chimp chromosomes with telomeres (which are present at the ends of chromosomes). Velasco argued that this fact makes the theory of common ancestry impossible to not be true since this means that humans and chimps shared a common ancestor.

Dr. Nelson argued the opposing argument which he defined as there not being one primordial form from which all of life has originated. Dr. Nelson stated that the main way biologists view common descent is by the notion that all life is related. The way they define "related" is by organism reproduction. He said that if relatedness is defined as organism reproduction, then we should not find a case in which two cells arise independently from each other. He asserted that the similarities between species that is observed could be explained by two ways: material descent and other physical reasons that have nothing to do with descent. Dr. Nelson declared that if there is a violation to the claim that nothing lies outside the tree of life domain - that is, nothing could have evolved outside the tree of life - then the claim that all of life is descended from a last universal common ancestor (LUCA) is false. He then used counterfactual conditional logic to format his argument by making the claim that If we saw X, then common descent would be wrong. Dr. Nelson then listed the following conditions as substitute for X: the machinery that the cell uses should not be divergent from LUCA and that phylogenies built on morphology should be congruent with phylogenies built on DNA basis. Dr. Nelson's strongest argument, and for which he is most known for, was that ORFan genes are divergent from LUCA and thus invalidate the common descent claim. ORFan genes are genes that do not have homologies in other lineages. They are taxon specific and arise through horizontal gene transfer or other mechanisms other than duplication, rearrangement, and mutation. The second argument that Dr. Nelson presented was that since there are multiple topoisomerases (which are cell machinery essential to DNA unwinding) from which come out of nowhere, this violates the counterfactual conditional on machinery. It was also noted that morphological phylogenies, that were created before the advent of DNA sequencing, do not match phylogenetic trees made on molecular data. Dr. Nelson then mentioned scientists who could not believe in the single tree of life model due to the vast genetic diversity of organisms found and summed up his argument by stating that a possible solution would be an intelligent designer.

Rebuttals

Dr. Velasco recognized that he only mentioned evidence for the domain of Eukarya. He said that he implied that everything else is related. He also said that though there are variants of the genetic code, they are very similar and only vary in one amino acid.

Dr. Nelson said that the consequence of debunking common descent is that the single tree of life model will break from the bottom up because you lose the significance of history if the origin of an organism can arise multiple times independently and he concluded by saying that this is what is happening right now.

My Impression

First, I found the subtitle on the flier of the debate, "Is evolutionary theory rock solid or deeply flawed?" misleading. The actual debate was not considering whether evolutionary theory itself was correct; rather, it discussed whether the majority of biologists are correct in thinking that all of life descended from one single common ancestor or if a few scientists, who think that there are phenomena that lie outside the tree of life, are correct. Since the event was in part presented by an evangelical church, I think that some people who attended this event thought that it was a debate of religion versus science; however, this was not the case.

Second, I found the structure of the debate to be inappropriate. It consisted of two philosophers who presented scientific ideas unrelated to philosophy. They discussed evolutionary theory, molecular genetics, and cell biology - all of which are scientific topics and I fail to see how two philosophers could be experts in a field of which they do not reside.

Third, they didn't even really debate each other. Dr. Velasco only addressed the similarities within the domain of Eukarya and did not even mention Bacteria or Archaea - the two other domains of life - in his main argument. He only rushingly mentioned that it was implied that all other life is also related. Dr. Velasco also did not even make any genetic arguments and the topic of which was the entire emphasis of Dr. Nelson's argument. Instead, Dr. Velasco focused on comparative anatomy, biogeography, and fossils which do not apply Dr. Nelson's arguments.

Lastly, the most concerning part about this debate was that I think that some of the audience members left with the idea that all of life did not descend from a single universal common ancestor, which is the opposite of the consensus that the scientific community holds.

Before Friday's debate, nine St. Edward's University science professors, the Dean of Natural Sciences, and the Director of the Wild Basin Creative Research Center all touched on this fact when they signed a Letter to the Editor of the St. Edward's University campus newspaper Hilltop Views. In a portion of the letter, they write:

We write to state clearly that the theory of evolution has undergone significant review in the scientific literature and remains the best, most coherent explanation of the observed development of life on Earth. While specific mechanisms within evolutionary theory remain the subject of modern research, we reiterate that subject of evolution itself is not up for debate in the scientific community.

Numerous scientific societies, including the American Association for the Advancement of Science, the American Astronomical Society, the American Chemical Society, the American Geophysical Union, the American Institute of Physics, the Federation of American Societies for Experimental Biology, and the National Academy of Sciences, have issued statements on the subject of evolution and intelligent design, confirming the demonstrated success of the former and rejecting the scientific viability of latter. The undersigned faculty in the School of Natural Sciences at St. Edward’s University fully embrace this point of view.

Though my view aligns with that of the aforementioned professors, I am not trying to say that the topics discussed in the debate should not be points of discussion; rather, I am merely trying to make the point that I think this debate would have been more appropriate if done with scientific experts. In doing so, this would have been a debate of the scientific minority versus the majority done by scientists themselves instead of philosophers.

Regardless, I applaud Dr. Dilley for organizing a successful debate that was very civil and respectful. Both Drs. Nelson and Velasco were very courteous to each other and their friendship, despite their differing opinions, was apparent throughout the discourse of the debate, which I think is one admirable trait we should all adopt.