Wednesday, June 18, 2008

Common Descent vs. Common Design

As I stated in my previous post, it seems to me that this “battle”, as Ken Miller refers to it, between the Evolution and Intelligent Design communities is based almost entirely upon religion, theology and philosophy. For years, I’d been convinced that the scientific elements of the debate could be discussed and concessions made so that both sides of the debate over origins could be considered in the science classroom without the unwanted drama.

Well, I was obviously seriously mistaken.

Then I started wondering if maybe they're right. Perhaps the issues being discussed between the advocates on both sides of the fence really have no beneficial consequence in the realm of scientific research. Rather, it seems that the concept of truth is what we're ultimately reaching for. Yet, when I think back to the Menuge/Myers debate, PZ Myers asserted that science is not about truth, but about what works. So, what is it about the concept of common descent that is so much more valuable to scientific research than common design?

How would a scientist’s work be affected if they were to adhere to the ID paradigm rather than the Darwinian paradigm, for instance? In other words, what’s the difference between the two concepts, and how would those differences affect the scientific research of two scientists working side by side while holding opposing views? Why is it considered a prerequisite to adhere to common descent, and how would a Darwinist soar ahead of the IDist due to his adherence to the notion that every single organism on planet earth evolved from that very first molecule through the mechanisms of evolution alone?

Scientists always point me toward nesting hierarchies and how important this information is to science. While I certainly agree, I wonder why the resulting research could only be met through strict adherence to the concept of common descent. Since Linneaus was classifying organisms before Darwin arrived on the scene, it seems to me that either belief (descent or design) would suffice in continuing these classifications throughout history. Scientists can predict that many organisms will share common similarities and differences under either assumption. The only way to confirm and document those organisms into a particular classification is to physically dig into the organism itself and see if your predictions are accurate. Your first predictions would be based on morphology (as much of Linneaus’ were), but as the hierarchy of biological classification's advanced, more information would come to light making it easier to predict where other organisms fall within their niche on the hierarchy charts. I’m still very confused as to why common descent is so important to the study of biology other than it’s an ingrained mind set making it impossible for scientists to realize that considering common design would produce virtually the same scientific results. The only difference that lies between the two camps are whether the mechanisms of evolution alone are capable of producing the results we observe in all of nature.

Maybe an example would be helpful here. The following is a question that was asked of me when I was visiting a pro-Darwin forum...

How does common design [rather than common descent] explain the difference between an ice fish and a similar related fish that still has functional globin genes?

I'm not talking about what you term "adaptation within a species". I'm talking about changes that occur between species, fish in this case. If you accept that microevolutionary changes can generate new species of fish, why do you have problems with evolution as an explanatory framework? You're an evolutionist.

OTOH, if you don't accept this sort of macroevolutionary change, you are basically saying that this closely related fish, with a functional globin gene is the same species as the Antarctic ice fish.

First of all, maybe we need to get our definitions in sync so that we aren’t talking past each other. So, let’s consider how scientists define species...
What is a Species?

Despite our increasing ability to understand the finest details of organisms, there is still debate about what constitutes a species. Definitions of species tend to fall into two main camps, the morphological and the biological species concepts.

-Morphological species concept: Oak trees look like oak trees, tigers look like tigers. Morphology refers to the form and structure of an organism or any of its parts. The morphological species concept supports the widely held view that "members of a species are individuals that look similar to one another." This school of thought was the basis for Linneaus' original classification, which is still broadly accepted and applicable today.

This concept became criticized by biologists because it was arbitrary. Many examples were found in which individuals of two populations were very hard to tell apart but would not mate with one another, suggesting that they were in fact different species.

Mimicry complexes supplied further evidence against the concept, as organisms of the same species can look very different, depending upon where they are reared or their life cycle stage (some insects produce a spring brood that looks like one host plant and a summer brood that looks like another).
The morphological species concept was replaced by another viewpoint that puts more emphasis on the biological differences between species.

-Biological species concept: This concept states that "a species is a group of actually or potentially interbreeding individuals who are reproductively isolated from other such groups."

This definition was attractive to biologists and became widely adopted by the 1940's. It suggested a critical test of species-hood: two individuals belong to the same species if their gametes can unite with each other under natural conditions to produce fertile offspring.

This concept also emphasized that a species is an evolutionary unit. Members share genes with other members of their species, and not with members of other species.

Although this definition clearly is attractive, it has problems. Can you test it on museum specimens or fossil data? Can it explain the existence of species in a line of descent, such as the well-known lineage of fossil horses? Obviously not.

In fact, one cannot apply this definition easily, or at all, with many living organisms. What if species do not live in the same place? What about the hybrids that we know occur in zoos? These problems are serious enough that some biologists recently argued for a return to the morphological species concept.
So what is the best way to define a species?

Most scientists feel that the biological species concept should be kept, but with some qualifications. It can only be used with living species, and cannot always be applied to species that do not live in the same place. The real test applies to species that have the potential to interbreed.

Most importantly, the biological species concept helps us ask how species are formed, because it focuses our attention on the question of how reproductive isolation comes about. Let us first examine types of reproductive isolation, because there are quite a few.

Obviously, ID supporters don’t question evolution at the microevolutionary level, although I’m well aware that the terms micro, macro, and species are defined in slightly different ways depending on whom you’re talking to and how convoluted the discussion becomes. But basically ID supporters question the ~extent~ to which the mechanisms of evolution are responsible for major morphological changes from one organism to the next throughout history. Some ID supporters have no qualms with the concept of common descent, while others critically consider the evidence supporting the notion that all of nature evolved from that first single molecule that arose from primordial sludge and find it wanting.

Empirical evidence is extremely rare in support of speciation, and the examples put forth by evolutionists are not impressive when considering the massive morphological changes and information packed organisms that have evolved since that first molecule started the evolutionary process. Where did that increase in information come from?

The loss in functionality of the globin gene in ice fish is a perfect example of evolutionary change. But, when one considers that a fish is a fish, this example does nothing more than provide an example supported with empirical evidence showcasing the ability that all organisms have to adapt to their environment. The loss of information in the ice fish could most certainly have resulted due to common ancestry among various species of fish. Natural selection is a wonderful thing, but just how much is this mechanism, along with the other mechanisms of evolution, capable of? That’s the pertinent question that many ID supporters consider.

So, as I address this type of question time and time again, I wonder if I’m not articulating my response correctly or if I’m still missing something. Perhaps some of the other ID supporters reading this post would be able to help me out. Is is vital that scientists adhere to common descent, and is this example of the globin gene impossible to concede to unless you do so?

Not only is speciation a major technical problem in evolutionary biology, but novel body plans are an enigma to Darwinism as we have never seen such changes take place. Virtually all the evidence is based on inference.

Consider Stephen Meyer’s peer-reviewed essay...
Novel Body Plans

The problems with the neo-Darwinian mechanism run deeper still. In order to explain the origin of the Cambrian animals, one must account not only for new proteins and cell types, but also for the origin of new body plans. Within the past decade, developmental biology has dramatically advanced our understanding of how body plans are built during ontogeny. In the process, it has also uncovered a profound difficulty for neo-Darwinism.

Significant morphological change in organisms requires attention to timing. Mutations in genes that are expressed late in the development of an organism will not affect the body plan. Mutations expressed early in development, however, could conceivably produce significant morphological change (Arthur 1997:21). Thus, events expressed early in the development of organisms have the only realistic chance of producing large-scale macroevolutionary change (Thomson 1992). As John and Miklos (1988:309) explain, macroevolutionary change requires alterations in the very early stages of ontogenesis.

Yet recent studies in developmental biology make clear that mutations expressed early in development typically have deleterious effects (Arthur 1997:21). For example, when early-acting body plan molecules, or morphogens such as bicoid (which helps to set up the anterior-posterior head-to-tail axis in Drosophila), are perturbed, development shuts down (Nusslein-Volhard & Wieschaus 1980, Lawrence & Struhl 1996, Muller & Newman 2003).5 The resulting embryos die. Moreover, there is a good reason for this. If an engineer modifies the length of the piston rods in an internal combustion engine without modifying the crankshaft accordingly, the engine won't start. Similarly, processes of development are tightly integrated spatially and temporally such that changes early in development will require a host of other coordinated changes in separate but functionally interrelated developmental processes downstream. For this reason, mutations will be much more likely to be deadly if they disrupt a functionally deeply-embedded structure such as a spinal column than if they affect more isolated anatomical features such as fingers (Kauffman 1995:200).

This problem has led to what McDonald (1983) has called “a great Darwinian paradox” (p. 93). McDonald notes that genes that are observed to vary within natural populations do not lead to major adaptive changes, while genes that could cause major changes--the very stuff of macroevolution--apparently do not vary. In other words, mutations of the kind that macroevolution doesn't need (namely, viable genetic mutations in DNA expressed late in development) do occur, but those that it does need (namely, beneficial body plan mutations expressed early in development) apparently don't occur.6 According to Darwin (1859:108) natural selection cannot act until favorable variations arise in a population. Yet there is no evidence from developmental genetics that the kind of variations required by neo-Darwinism--namely, favorable body plan mutations--ever occur.

Developmental biology has raised another formidable problem for the mutation/selection mechanism. Embryological evidence has long shown that DNA does not wholly determine morphological form (Goodwin 1985, Nijhout 1990, Sapp 1987, Muller & Newman 2003), suggesting that mutations in DNA alone cannot account for the morphological changes required to build a new body plan.

Consider this: To claim that something like bacteria evolved into birds and humans, you must consider that the hypothetical series of steps had to traverse hundreds of vital organs. After a new vital organ evolved, one should wonder how the organism had survived before it had that vital organ, because without the newly evolved vital organ, the “critter” is (by the definition of vital) dead! Macroevolution must produce greater complexity which requires large increases in information. New vital organs and irreducible complexity would be examples of greater complexity. Where is the empirical evidence that this has actually occurred? Can you show me any natural process that produces large, nontrivial amounts of information? Natural processes tend to destroy information. All living things contain gigantic amounts of information! Here’s a question for the scientists out date, what are some of the most beneficial mutations to organisms in their natural environments that scientists have observed through the years?

In regard to the ice fish example, whether you consider the loss of the globin gene a significant evolutionary change at the species level is certainly in the eye of the beholder. Again, the mutation that occurred resulted in a loss of information. The fact that we can provide empirical evidence of this type that implies that the ice fish evolved from a related ~fish~ is not significant in regard to the question of design vs. common descent.

Something else that was directed toward me in the forum discussion was this accusation...
The onus is on you to show that common design has this sort of explanatory power, NOT to cast stones at the current paradigm. If your paradigm is as good as the current one, prove it.

First of all, the explanatory power of natural selection is not in question, and virtually every piece of empirical evidence used by scientists to support common descent are microevolutionary changes which are also a part of the design “paradigm”, if you will. Second, I most certainly have the right to cast stones at the current paradigm without providing you with a new one. Consider the following...

Norman Macbeth wrote a brilliant treatise in 1971, Darwin Retried: An Appeal to Reason. The book was endorsed by Sir Karl Popper, the great philosopher of science. Macbeth, a skilled lawyer (J.D. from Harvard) with razor-sharp logic, was invited to join the monthly meetings of the curators of the American Museum of Natural History. The discussions usually dealt with evolution; namely, how could it have happened. Macbeth responded to this type of accusation that one must provide an alternative explanation rather than “cast stones at the current paradigm”. Macbeth wrote on pages 5–7:

The proponents of a theory, in science or elsewhere, are obligated to support every link in the chain of reasoning, whereas a critic or skeptic may peck at any aspect of the theory, testing it for flaws. He is not obligated to set up any theory of his own or to offer any alternative explanations. He can be purely negative if he so desires. ...

I have been rather surprised to discover that many biologists dispute the propriety of a purely skeptical position. They assert that the skeptic is obligated to provide a better theory than the one he attacks. Thus Professor Ernst Mayr of Harvard rules out admittedly valid objections on the grounds that the objectors have not advanced a better suggestion. I thought at first that this was a personal foible of Mayr’s, but it has recurred in so many other places that it must be a widespread opinion.

So, in conclusion, I guess I question whether either paradigm (Design or Darwinism) would produce more fruitful research over the other? It seems to me that the arguments center on philosophy and a quest for truth in science rather than a means in which to advance scientific research.


I welcome all comments, but I will allow them with a few stipulations. Dialogue must be respectful. If you feel it mandatory to talk down to me, you’ll be walking on very thin ice. If you bring up YE arguments, your comments will be immediately deleted because this post is in reference to ID and common descent.



Dr. Walter Brown - via this dialogue thread. I have paraphrased or transcribed in full several sentences from Brown’s responses in that particular thread discussion.

Also: The Process of Speciation

Edit: 6/19 for clarity