May 14 2013

An Interview with Don McLeroy, Part II

In part I of my analysis of a recent interview with Don McLeroy on the SGU I discussed his assertion that those of faith are more free to accept or reject the evidence for evolution, while strict materialists can only accept it as it is the only materialist option. I mentioned in that post that I would invite Don to respond – I did and he did.

In this post I will include Don’s response and then my further analysis of his response. I will then extend the discussion to other points that Don raised during the SGU interview.

Don McLeroy Responds to Part I


Thank you for this opportunity to respond.

We are mirror images of each other. I see you as you see me-as “an excellent example of the power of motivated reasoning,” as “firmly in phase 2,” and as someone who might be considered “embedded” in a culture of their own publications, institutions, and websites.

At least we both agree to follow the evidence where ever it leads.

I do now admit that I was wrong about the atheist being compelled only to accept evolution; the atheist is also free to follow the evidence in another direction or say “I do not know.” As you wrote, “If the evidence were ambiguous or scant, than perhaps the current answer would be, we don’t know.”

In fact, I believe this is a perfectly satisfactorily answer for both the creationist and the atheist. Let us allow the students to evaluate the evidence for themselves. Concerning the Texas standards amended by the board, the Fordham report on state science standards stated “There are no concessions to ‘controversies’ or ‘alternative theories.’ In fact, the high school biology course is exemplary in its choice and presentation of topics, including its thorough consideration of biological evolution.” In Texas, we have not abandoned the “scientific consensus.”

The Austin American-Statesman opinions editor invited me to write an op-ed after the report was released.

Where the board amended the standards on evolution, Fordham described them as “exemplary”, where we accepted the standards as submitted by our writing panels, they criticized them. I guess we needed more “creationist” oversight.

My main critique of your post is an apparent confusion about the nature of science. You state “Science is about providing natural explanations.” and then later state “science is about producing testable theories that make predictions about how nature will behave.” I agree with the latter; the key criterion of science is testability. I believe it is the job of science to test theories-not to provide natural explanations.


False Equivalency

It is my opinion (shared by many skeptics and scientists) that creationism is a form of denialism – it is evolution denial.  Throughout this discussion I will point out the features in Don’s position that are typical of the denialist strategy. The first is known as false equivalency – specifically that between evolutionary theory and creationism.

Don’s opening paragraph is the clearest expression of false equivalency I can recall – noting that our positions are “mirror images” of each other. If my position is embedded in any culture, it is that of the broad international scientific community. My position reflects the overwhelming scientific consensus in common descent and evolutionary change over time.

Don’s position, by contrast, is embedded in a particular sect of a religion, one that has had significant conflict with mainstream science when it conflicts with their religious dogma. The two situations are not equivalent.

This also gets to the heart of the context of this discussion – what gets taught is public school science classrooms. It should be clear that what gets taught as science is the consensus of scientific opinion, not the beliefs of one religious sect.

Don’s response to this, reflected in the interview and in his response above, is that the Texas science textbook standards reflect science, and do not insert mention of God or creationism into the books. It can be clearly established, however (documented by those following this debate over the years) that this is just the latest strategy of creationist opposition to the teaching of evolution in public schools.

There is no mention of God or creationism now – only after several Supreme Court decisions struck down those strategies. Insertion of “strengths and weaknesses” language is the current strategy, that Don reflects quite well. Such strategies unfairly target evolution, however, and the “weaknesses” that are referred to are imaginary pseudoscientific creationist arguments that have already been thoroughly refuted by scientists.

With regard to “natural explanations” I think Don misunderstood my point. The natural explanations that science provides need to be testable – these are not exclusive features of science. The points of mentioning “natural explanation” was to emphasize “natural,” as opposed to supernatural.

These two features of science are, in fact, inextricably related. Only naturalistic explanations are testable. Supernatural explanations are not, because by definition they are not constrained by natural laws and can therefore never be falsified. (I discuss this point further here and here.)

Let’s move on to some new issues raised in the interview.

“Stasis” and “Sudden Appearance”

Don brought up in the SGU interview the language he managed to have inserted in the Texas science textbook standards, “analyze and evaluate the sufficiency or insufficiency of common ancestry to explain the sudden appearance, stasis, and sequential nature of groups in the fossil record.”

He wants students to decide for themselves if the fossil evidence supports evolution or not. This always superficially sounds reasonable, but the counterpoint I brought up during the interview was that we send a powerful message to students by what we choose to present and emphasize. Even presenting stasis and “sudden” appearance as a problem for evolutionary theory or common descent is misleading, because they aren’t.

Don acknowledged that the sequential nature of the fossil record is compelling evidence for evolution, and that he can understand how people would arrive at that conclusion. He thinks this is the most powerful evidence for evolution. I disagree – by far the most powerful evidence for evolution is the genetic and molecular evidence. Perhaps I can entice Don into analyzing and responding to this evidence.

I suspect he positions the fossil record as the strongest evidence for evolution because he feels he can then knock it down with his stasis and sudden appearance argument. This is really a very old creationist argument, dismantled decades ago. Steven D. Schafersman has an excellent discussion on this topic, but I will summarize.

When we look at the entire fossil record what we see are the first appearance of hard parts around 542 million years ago during the Cambrian Explosion (more on this later). These first multicellular organisms were simple compared to later life, but all modern phyla are represented, but many that are now extinct. In the last 500 million years we see new species arise in the fossil record, with clear antecedents. In other words, entirely new body plans do not arise out of nowhere. New species are always variations on older species. Further, species have a definite lifespan in the fossil record – they are not spread randomly over time.

In addition to this sequential nature of the fossil record, there appears to be an overall pattern of nested hierarchies. Apes appear closely related, but can also be grouped with all primates, who can be grouped with all placental mammals, who can be grouped with all mammals, who can be grouped with all vertebrates, etc.

These patterns reflect common descent and are exquisitely evolutionary. As an added feature, species also appear to be geographically located in an evolutionary pattern. Mammals in Australia are more closely related to each other than they are to mammals in North America.

There are also numerous transitional fossils – linking individual species, and major groups. The discovery of a large number of feathered dinosaurs, for example, nicely bridges the gap between birds and theropods. Ambulocetus, the walking whale, nicely links whales and terrestrial mammals – these represent a compelling morphological and temporal sequence.

In Darwin’s time the fossil record was very scant. Evolutionary theory predicted that as the fossil record emerged it would reveal a pattern consistent with evolution, and it has, in spades. There is no legitimate scientific refutation to the implications of this massive amount of physical evidence – evolution happened.

Don does not even try (at least in the interview) to refute this evidence. Rather he employs a common denialist strategy of focusing on smaller details as if they are capable of disproving the bigger picture. This is a fundamental misunderstanding of how science operates (which is why scientists are so concerned about inserting these ideas into science standards – they confuse students about how science operates).

The details about how genes work and are organized do not call into question whether or not DNA is the molecule that carries inherited information. The deviations from a perfect sphere in the Earth’s shape cannot be used as evidence that the Earth is actually a cube (it is still basically a sphere, or an oblate spheroid to be technical).

Likewise, details about the pace and tempo of evolution do not even address let alone call into question the sequential,  hierarchical, and geographical patterns in the fossil record that scream evolution and common descent.

Stasis and sudden appearance are not problems for evolution or common descent, nor are they the only patterns we see in the fossil record. Some species do gradually change over time in the record, for example.

Gould and Eldridge proposed a very nice hypothesis about stasis and sudden appearance – punctuated equilibrium. Speciation events tend to be geologically rapid. “Sudden” in this context means between 5 and 50 thousand years. Five thousand years at the low end is still many generations, and is not sudden in terms of evolutionary processes. Creationists misuse the term “sudden” in the context of the geological record and apply it to biological processes in a deceptive way.

The apparent stasis of many species in the fossil record Gould and Eldridge explained as species being in equilibrium with their environment. Research has born this out. Once a species is comfortably optimized to their niche, selective pressures will maintain their optimal state. If the environment changes, species are most likely to simply migrate, to track to an environment to which they are already adapted.

Occasionally species are pushed out of equilibrium with their environment – they colonize an island, adopt a new strategy of survival, a new predator or prey species enters their environment, or climate change significantly alters their environment. Those that don’t or cannot migrate to a better environment, must evolve or die. It makes sense that a species out of equilibrium must adapt quickly – within thousands of years.

Again – this is a dominant feature of the fossil record, but is by no means universal. It also in no way calls into question the bigger picture in the record.


The fossil record is very powerful evidence for evolution (and not even the most powerful). The fact that many species appear suddenly in the record, persist for a few million years on average, then go extinct is completely compatible with evolutionary theory and common descent, and is nicely explained by the current modern synthesis of evolutionary theory. The details are likely to be tweaked as new evidence emerges, but those details do not touch the bigger picture of common descent.

It is also important to point out, and a common part of the denialist strategy, that the fossil record in no way supports young earth creationism. If there was one creation over a six “day” period (however you interpret “day”) then why is there a fossil record showing a sequential pattern of nested hierarchies?

That fact is a fatal problem for creationism, while stasis and rapid appearance is not a problem at all for evolution. This reflects the creationist strategy, however, of not even bothering to build a body of evidence for creationism, but rather to just chip away at the evidence for evolution, and then declare victory for creationism by default (a false dichotomy logical fallacy).

The fossil record is clear evidence that evolution occurred, and was predicted by Darwin’s theory. The fossil record could have turned out very differently – there are countless patterns that would have falsified evolution (horses in the Cambrian strata, new body plans popping up out of nowhere, impossible chimeras, lack of a temporal sequence), but none of them were found.

The higher resolution details of the record tell us about what evolved from what and when, and the pace and tempo of evolution, but do not address the larger pattern of common descent. This hierarchical confusion is again typical of denialists. 

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