EPS Article Library
Atheists Against Darwinism - Page 12
Nagel carefully distinguishes skepticism about adaptationalism from advocating design: "Skepticism about the standard evolutionary model is not limited to defenders of ID." Nagel re-iterates the significance of Behe's argument:
even if one merely regards the randomness of the sources of variation as an open question, it seems to call for the consideration of alternatives . . . A great deal depends on the likelihood that the complex chemical systems we observe arose through a sufficiently long sequence of random mutations in DNA, each of which enhanced fitness. It is difficult to find in the accessible literature the grounds for evolutionary biologists" confidence about this.
Confidence expressed by Jerry Coyne . . . in his review of The Edge of Evolution: "Behe furnishes no proof, no convincing argument, that [protein- protein] interactions cannot evolve gradually. In fact, interactions between proteins, like any complex interaction, were certainly built up step by mutational step, with each change producing an interaction scrutinized by selection and retained if it enhanced an organism's fitness" (The New Republic, June 18, 2007, p. 42).
Behe does not argue that protein-protein interactions "cannot evolve gradually", but that "complexes with more than two different binding sites ? ones that require three or more different kinds of proteins ? are beyond the edge of evolution." And Behe does furnish "proof":
Where is it reasonable to draw the edge of evolution? . . . On the one side are our very best examples ? from humanity's trench war with parasites ? of what random mutation and natural selection are known to do. We know that single changes to single genes can sometimes elicit a significant beneficial effect. The classic example? is that of sickle cell hemoglobin, where a change to one amino acid confers resistance to malaria . . . More rarely, several mutations can sequentially add to each other to improve an organisms' chances of survival. An example is the breaking of the regulatory controls of fetal hemoglobin to help alleviate sickle cell disease. Very, very rarely, several amino acid mutations appear simultaneously to confer a beneficial effect, such as in chloroquine resistance? in malaria? a "CCC," a "chloroquine-complexity cluster," . . . A CCC requires, on average, 1020, a hundred billion billion, organisms ? more than the number of mammals that has ever existed on earth. So if other things were equal, the likelihood of getting two new binding sites would be . . . the square of a CCC, or one in ten to the fortieth power. Since that's more cells than likely to have ever existed on earth, such an event would not be expected to have happened by Darwinian processes in the history of the world. Admittedly, statistics are all about averages, so some freak event like this might happen . . . But it is not biologically reasonable to expect it, or less likely events that occurred in the common descent of life on earth . . . complexes of just three or more different proteins are beyond the edge of evolution.
Nagel cautions Darwinists:
It is not enough to say . . . that the incapacity of evolutionary mechanisms to account for the entire evolution of life has not been conclusively established. That is not required for an alternative to be considered seriously, provided the alternative is not ruled out in advance on other grounds. Those who offer empirical evidence for ID do not have to argue that a completely non-purposive explanation is impossible, only that it is very unlikely, given the evidence available. That is a scientific claim, though a contestable one.
This is precisely what Behe argues. Indeed, peer-reviewed scientific debate about Behe's empirical argument is ongoing. Whilst withholding agreement from Behe, Nagel affirms that no empirical refutation of ID:
has ever been offered, let alone established. What have been offered instead are necessarily speculative proposals about how the problems posed by Behe might be handled by evolutionary theory, declarations that no hypothesis involving divine intervention counts as science, and assurances that evolutionary theory is not inconsistent with the existence of God.1 2 3 4 5 6 7 8 9 10 11 12 13 14