The Dutch biologist Gert Korthof maintains a website devoted to in-depth reviews of many books on evolution. Aside from often-insightful remarks, a delightful feature of his site is that he can write with great strength of feeling and yet not engage in insults or ad hominem remarks. He has posted an extensive review of The Edge of Evolution.
He makes two main points. First, that while I profess to believe in both common descent and intelligent design, he sees an internal contradiction — there cannot be, he thinks, common descent if there is intelligent design, and vice versa. The second point is that he thinks I contradict what I wrote in Darwin’s Black Box concerning the status of pseudogenes as evidence of common descent. I’ll take these points in turn.
The “designed group” contains at least Kingdoms, Phyla, Classes (and maybe Orders, Families and Genera). Behe’s “randomness group” contains at least species (and maybe genera, families and orders).
“Explicit design appears to reach into biology to a certain level, to the level of the vertebrate class, but not necessarily further” (p. 220)
Apparently the vertebrate class is explicitly designed. That means that at a certain moment in the history of the earth the first vertebrate “was designed”. The fundamental problem here is that the reason for invoking design is that natural processes are not sufficient to produce vertebrates. However, as soon as one single nonnatural event is invoked during the history of life, the genetic continuity of life is broken. Common Descent is based on the vertical (sometimes horizontal) transmission of genetic information. Without that genetic continuity, Common Descent breaks down.
Korthof is incorrect here. As I read him, Korthof is saying that the first moment that some vertebrate class appeared was the moment that it was designed. Thus there is a discontinuity that can’t be classified as common descent. But as I tried to make clear especially in the last chapter of my book, all design might have been built into the initial conditions of the universe and unfolded over time. I try to get this point across with the figure of the überphysicist who selects a certain one out of very many universes which will develop in just the way he wishes; he “activates it”; and from there on everything follows according to unbroken natural law. It may be that in that universe there are some apparently amazing coincidences and astronomically low-probability events [which were front-loaded into the initial set-up], but all events follow without further prodding after the initial activation. Thus, contra Gert Korthof, there can indeed be purposeful intelligent design and common descent.
Concerning the second point — the status of pseudogenes, Korthof writes:
Here [in Darwin’s Black Box] Behe argues against Ken Miller. Miller claimed that Intelligent Design cannot explain pseudogenes of hemoglobin in humans, because it would mean that “the designer made serious errors, wasting millions of bases of DNA on a blueprint full of junk. Evolution can explain them as nothing more than failed experiments”. Indeed, it is true that in general one cannot conclude from structures with unknown function to no function at all, but the pseudogene is not an unknown structure, but a copy of a known functional gene with mutations which make it non-functional. So Behe’s critique fails. Behe’s second argument against pseudogenes as evidence for Common Descent is that “even if pseudogenes have no function, evolution has “explained” nothing about how pseudogenes arose” (DBB,226) and his third is that “these chance events do not mean that the initial biochemical systems were not designed.” (DBB,228).
My point is not to refute Behe’s arguments, but simply point out the amazing and extraordinary fact that Behe in Darwin’s Black Box dismissed exactly the same evidence that he now accepts without any explanation. In The Edge he simply states “a broken hemoglobin gene” and forgets that he stated 10 years ago that “this argument is unconvincing for three reasons”. What was exactly wrong with his arguments in DBB?
This topic is actually pretty simple, but can get confusing if you take your eye off the ball. I take pseudogenes as good evidence of common descent, both in Darwin’s Black Box and The Edge. However, I do not take pseudogenes as evidence that random mutation and natural selection could have produced the original functioning gene which eventually gave rise to a pseudogene. Kenneth Miller was trying to argue that pseudogenes are positive evidence against all intelligent design. In my mind that’s like arguing that a broken down car is evidence against intelligent design. Miller’s argument was incorrect. But Korthof takes my rebuttal as arguing against common descent, which it wasn’t meant to do. It was an argument that pseudogenes do not speak to the ability of Darwinian processes to make functioning genes.
I think a lot of folks get confused because they think that all events have to be assigned en masse to either the category of chance or to that of design. I disagree. We live in a universe containing both real chance and real design. Chance events do happen (and can be useful historical markers of common descent), but they don’t explain the background elegance and functional complexity of nature. That required design.