Why Darwin Matters_ The Case Against Intelligent Design - Michael Shermer [37]
We Cannot Observe Evolution: No laboratory experiments or field observations reveal evolution in action.
Another regular on the Intelligent Design circuit is the hunt for “evolution in action.” Scientists have not, and probably can never, provide examples of evolution at work that would satisfy an Intelligent Design creationist. It is one thing to infer in the fossil record the creation of a new anatomical structure, or the birth of a new species; it is quite another to witness it in the laboratory. And what examples we do have of evolution in action in the lab, creationists claim is not evolution.
But not only does science have an incredibly rich fossil record, the process of evolution can be seen at work at a number of different levels. Diseases are prime examples of natural selection and evolution at work, and on time scales we can witness, all too painfully. The AIDS virus, for example, continues to evolve in response to the drugs used to combat it—the few surviving strains of the virus continue to multiply, passing on their drug-resistant genes. Creationists respond that this is an example of microevolution, not macroevolution. Fair enough.
For an example of macroevolution, then, check out the research by the University of Michigan biologist James Bardwell, reported in the February 20, 2004, edition of Science, in which an E. coli bacterium that was forced to adapt or perish improvised a novel molecular tool. “The bacteria reached for a tool that they had, and made it do something it doesn’t normally do. We caught evolution in the act of making a big step.” The big step was a new way of making molecular bolts called disulfide bonds, which are stiffening struts in proteins that also help the proteins fold into their proper, functional, three-dimensional shapes. This new method restarted the bacterium’s motor and enabled it to move toward food before it starved to death.
It is a particularly important experiment because Bardwell developed a strain of mutant bacteria unable to make disulfide bonds, which are critical for the ability of a bacterium’s flagellum to work—the same flagellum that Intelligent Design theorists are so fond of presenting as an example of irreducible complexity. The researchers put these nonswimming bacteria to the test by placing them on a dish of food where, once they had exhausted the food they could reach, they either had to repair the broken motor or starve. The bacteria used in the experiment were forced to use a protein called thioredoxin, which normally destroys disulfide bonds, to make the bonds instead. In a process similar to natural selection, one researcher made random alterations in the DNA encoding thioredoxin and then subjected thousands of bacteria to the swim-or-starve test. He wanted to see if an altered version of thioredoxin could be coerced to make disulfides for other proteins in the bacteria. Remarkably, a mutant carrying only two amino acid changes—amounting to less than 2 percent of the total number of amino acids in thioredoxin—restored the ability of the bacteria to move. The altered thioredoxin was able to carry out disulfide bond formation in numerous other bacterial proteins all by itself, without relying on any of the components of the natural disulfide bond pathway. The mutant bacteria managed to solve the problem in time, swim away from starvation, and multiply.
Of course, Intelligent Design