Neurosurgeon and recent addition to the Discovery Institute’s Media Complaints Division blog Dr. Michael Egnor is at it again. He’s responded to Burt’s latest response to his prior response to Burt’s earlier response to his - you get the drift. Burt’s been doing a great job of responding to Egnor, and I don’t want to step on his toes, but Egnor says a couple of things this time that I think would benefit from the perspective of someone who is studying evolutionary biology.

First, though, I’d like to address this delightful bit of less-than-honest rhetoric:

In addition, a common Darwinist argument is that the presence on medical school faculties of scientists who study some aspects of evolutionary biology is evidence that evolutionary biology is indispensable to medicine. That argument is flawed, but it does raise an important issue.

Actually, Dr. Egnor, if you look back through your exchange with Dr. Humburg, you will see that you were the one who brought up faculty composition at medical schools. If you’ll recall, you said this in your opening entry:

Doctors don’t study evolution. Doctors never study it in medical school, and they never use evolutionary biology in their practice. There are no courses in medical school on evolution. There are no ‘professors of evolution’ in medical schools. There are no departments of evolutionary biology in medical schools.

Let’s look at the sequence of events one more time:

1: Egnor argues that the lack of “professors of evolution” in medical schools is evidence that evolution is irrelevant to medicine.

2: Burt points out the fact that there are plenty of medical school professors who have research programs that focus on evolution.

3: Egnor claims that Burt was arguing that the presence of evolutionary biologists (aka “professors of evolution”) is evidence that evolution is relevant to medicine.

4: Egnor claims that the argument in point 3 is flawed.

Nice chain of argument there.

Now, on to evolutionary biology.

Egnor writes:

These fine scientists do not, however, contribute to medicine by studying or teaching evolutionary biology. They contribute to medicine by their work in anatomy, or physiology, or microbiology, or molecular biology. The central assertion of Darwinism–that all biological complexity arises by random heritable variation and natural selection–is of interest to evolutionary biologists (and to those of us who disagree with it), but the assertion that randomness is the raw material for all biological complexity plays no role in medical education or research. Darwin’s assertion of randomness is irrelevant not only to medicine, but to much of biological science. Darwinism is, in Phillip Skell’s apt phrase, a narrative gloss applied to biology and highly superfluous. Teaching medical students about the anatomy of the brain or the molecular structure of DNA is very important. Teaching students about Darwinian speculations about the random origins of the brain or of DNA adds nothing to students’ knowledge of medicine.

As someone who studies evolutionary biology, I have a lot of problems with Egnor’s description of it. To be blunt, it’s a strawman, pretty much from top to bottom.

Let’s start with Egnor’s description of the “central assertion of Darwinism.” Actually, before we get to the description, I have a problem with that phrase itself. The mechanism of evolution by natural selection is not an “assertion.” It is a theory. It is not a dogmatic truth that must be accepted. It is a hypothesis that has been tested, retested, and tested some more, and that has done quite well along the way.

Moving on to the description itself, Egnor claims that “Darwinism” “asserts:”

that all biological complexity arises by random heritable variation and natural selection

Egnor, like many other anti-evolutionists, seems to object more to the “random” nature of evolution than anything else. In this case, I find that to be more than a little funny, since the only difference between what Darwin actually argued and what Egnor thinks Darwin argued results from Egnor’s use of the word “random.”

The theory of evolution by natural selection simply states that species change as a result of the process of natural selection acting on heritable variations. For the purposes of natural selection, it doesn’t matter whether the variation is random or not. Given a set of heritable variations that result in different probabilities of successful reproduction, natural selection will act to increase the frequency of the variants that make reproduction more likely. If, tomorrow, I were to use genetic techniques to add a new gene to a wild population, natural selection would act on the gene I added in the same way that it acts on any other gene.

So, if “random” isn’t a necessary condition of natural selection, where does it come from?

In science, “randomness” is a null hypothesis. It is the default position that we take unless there is strong evidence that this is not the case. This is not unique to evolution. It’s the way almost all scientific hypotheses are tested these days. If you want to know if a finding is significant, you usually ask if the differences between the things you are looking at differ from what you would expect if random chance was the only factor involved.

In genetics, the null hypothesis is that mutations occur randomly. If there is enough evidence that mutations are taking place in a non-random fashion under certain circumstances, the null hypothesis will be rejected under those circumstances. There are different types of mutation. For most of those, the null has not been rejected. “Random mutation” is not an assertion of evolutionary biology. It is our best scientific understanding of how mutation takes place, it is an easily tested null hypothesis that has not been rejected.

If you don’t like the idea that mutations are random, your argument isn’t with Darwin. It’s with nature.

Moving on, Egnor talks about “Darwin’s assertion of randomness.” Here’s what Darwin actually had to say about why he treated variation as random (this quote comes from the beginning of chapter 5 of the 6th edition of Origin of Species):

I have hitherto sometimes spoken as if the variations – so common and multiform with organic beings under domestication, and in a lesser degree with those under nature – were due to chance. This, of course, is a wholly incorrect expression, but it serves to acknowledge plainly our ignorance of the cause of each particular variation.

Darwin, like modern scientists, did not assert that variation was random. He simply used it as a null hypothesis.

Now we get to the last, and most objectionable, part of Egnor’s mischaracterization of evolution:

Teaching students about Darwinian speculations about the random origins of the brain or of DNA adds nothing to students’ knowledge of medicine.

I know of absolutely no evolutionary biologist who would call the origin of the brain – or, for that matter, the eye, the stomach, the heart, the lungs, the gills, the fins, etc – “random.” Natural selection is a fundamentally non-random process. It does not preserve variants at random. It selects (hence the name) variants non-randomly, based on their effect on the organism’s ability to produce the next variation.

Anyone who thinks that natural selection is a random process clearly does not understand natural selection, and is definitely not qualified to discuss evolution.