24 August 2007
Michael J. Behe
As I wrote in The Edge of Evolution, Darwinism is a multifaceted theory, and to properly evaluate the theory one has to be very careful not to confuse its different aspects. Common descent, natural selection, and random mutation are separate concepts; the first two are well supported, but the power of random mutation is not. I argued that evolution — understood just as common descent — did happen, but that randomness played only a minor part. Instead, nonrandom processes — either front-loaded, guided, or somehow influenced by an intelligence — played by far the greatest part.
Unfortunately, stories in the news and on the internet regularly confuse the facets of Darwinism, ignore distinctions made in The Edge of Evolution, or misstate the arguments of intelligent design. The disregard for critical distinctions blurs the issues badly. This is the first in an occasional series of brief posts to correct confusions.
A recent New York Times story by Kenneth Chang touted a new paper in Science by the laboratory of Joseph Thornton of the University of Oregon as refuting intelligent design. Thornton’s laboratory has been interested in the evolutionary development of differences between two proteins abbreviated GR and MR. Since the two proteins are very similar, and since they bind very similar small hormone molecules, they likely developed from an ancestral gene by gene duplication and subsequent diversification. Despite Chang’s story, none of that challenges intelligent design, which agrees that minor evolutionary changes can happen by random mutation and natural selection.
The gist of the new paper is that the workers reconstructed in the lab what they thought would be the ancestral protein, as well as several later evolutionary versions of it. To get to a protein mimicking modern GR, they purposely introduced several mutations to the ancestral form. The first few mutations took the protein’s activity part of the way toward the modern activity. But adding several other mutations that they thought would increase the specific activity to that of modern GR unexpectedly caused the protein to lose all its ability to bind the hormones. So, after thinking awhile, the authors then went back and intentionally introduced other mutations which did not affect hormone binding, but which they hoped would strengthen a particular part of the protein. After deliberately strengthening that part, they found they could add the final mutations, the protein would retain its activity, and its activity would be much more similar to modern GR.
Now, dear reader, can you guess which parts of Darwin’s theory this all neglects? Of course — both random mutation and natural selection. The workers nicely showed it is quite reasonable to think that the one ancestor protein could produce two descendants, but they didn’t even try to address the question of whether it could happen by chance plus selection. Of course, getting a single amino acid mutation by chance is not a problem. But in order to have the mutation be positively selected, it has to benefit an organism. The authors (and news stories) completely ignore that — the authors didn’t measure whether duplicating the ancestral gene, and then modifying it, would benefit an organism that was used to relying on just one protein (admittedly that would be hard to do). What’s more, in order to be confident that a multi-mutation scenario reconstructs a Darwinian process, all subsequent mutations have to be positively selected, too.
But they aren’t. Although they test none of the mutations in actual organisms, the authors themselves feel that the very particular mutations they deliberately introduced, which strengthen the protein but don’t affect hormone binding, would have been neutral. That makes those mutations much, much less likely to spread in a population, to be available later for when the beneficial mutations came along. In other words, the authors themselves think the scenario involves a big stroke of luck. In theNew York Times Chang quotes Thornton: “‘These very exquisitely adapted bodies we have represent a role of the dice,’ Dr. Thornton said. ‘And they could have turned out very differently.’”
Big strokes of “luck,” however, point much more to intelligent design than to Darwinism. If evolution were guided or designed to unfold in a particular way, then very improbable events would be expected to be packed into it. The bottom line is that, while the new paper is very clever work, it offers no support at all to Darwinism. If anything, the authors careful work points strongly away from randomness. If even such minor evolutionary differences as those between GR and MR are problems for chance-driven evolution, greater evolutionary difference are almost certainly beyond the edge of random evolution.