Mary Midgley’s “A Plague on Both Their Houses” purports to set the record straight about ID and evolution. ID is bad science, and evolution, when used to justify atheism, is bad philosophy. If both sides in this debate could only recognize the proper limits of science and philosophy, we could dispense with this needless controversy.
Midgley’s analysis is disappointing. For it to work, ID’s scientific critique of and its counterproposal to standard evolutionary theory must fail. And for Midgley it does, as follows:
Biologists have pointed out the feebleness of the mechanical analogy, of course. Organisms and their parts do not consist of separate items that must be put together deliberately in the workshop, but of continuous tissue, areas of which often have several different functions and can shift between them by what is called ‘co-option’. No helpful designer was needed in order to provide a cow with a fly-whisk: cows themselves acquired one merely by using a rather undifferentiated tail in a new way. But the public which is impressed by ID theory does not read these replies.
The public, insofar as it has read the ID literature, has read these replies because the ID literature treats Midgley’s co-option approach to building biological complexity at length — and shows it to be deficient. It is remarkable that Midgley refers to organisms as consisting of “continuous tissue” as though this undercuts the ID proponents’ “mechanical analogy.” ID stakes its claim at the level of molecular biology, not at the level of “continuous tissues.” At the level of molecular biology, we have protein machines that are machines literally and not just analogically. Consider the following remark by Adam Wilkins, the editor of BioEssays, in his introduction to the December 2003 special issue on molecular machines:
The articles included in this issue demonstrate some striking parallels between artifactual and biological/molecular machines. In the first place, molecular machines, like man-made machines, perform highly specific functions. Second, the macromolecular machine complexes feature multiple parts that interact in distinct and precise ways, with defined inputs and outputs. Third, many of these machines have parts that can be used in other molecular machines (at least, with slight modification), comparable to the interchangeable parts of artificial machines. Finally, and not least, they have the cardinal attribute of machines: they all convert energy into some form of ‘work’.
Yes, organisms are more than machines, but at the subcellular level they contain machines — actual machines. Moreover, co-option hardly explains how such molecular machines might have arisen (see, for instance, chapter 6 of THE DESIGN OF LIFE).
Midgley concludes her essay by remarking, “It seems to me that ID is going to give us a great deal of trouble.” If the “us” here is smug cossetted intellectuals who think caricaturing ID is the same as refuting it, she is probably right.