Evolution Revealed
One of the canards used by my fellow Christians who actively fight against the idea of evolution is that it can’t be proven because it can’t be observed. Scientists are observing evolution in carefully conducted tests that challenge some of their preconceptions. Those preconceptions, however, do not address the basic core of evolutionary thought, but rather the specific mechanisms under which evolution occurs. One recent experiment with E.coli bacteria is summarized by Panda’s Thumb:
These bacteria have been raised in a constant environment, one which is somewhat less than ideal: they’ve been fed on small quantities of glucose, and nothing but glucose, in a lean regimen that has encouraged selection for somewhat different properties than you’ll find in your gut, one of the normal habitats of E. coli. They have evolved, and even have distinctive morphological characters, and many of their properties are consistent from population to population. There is one property that would be useful for the bacteria, but that has evolved in only one of the 12 populations: the ability to use citrate as a carbon source. There’s plenty of citrate in the medium, and it would be a bit of a coup for any bacterium to acquire the ability to take up and metabolize it, but it just hasn’t happened as often as might be hoped…except in one of the 12 populations, which around the 33,000th generation, suddenly expanded its stable population size by exploiting citrate in its environment.
PZ Myers, the author, explains that the preconceptions that are challenged by this development, and they are not in any way challenges to the general understanding of evolution. We lay people often get it wrong when science discovers something new that “challenges” what has come before; for us, it is hardly a challenge at all, but merely a small correction. The scientists observed that only one of the 12 populations evolved the ability to use the citrate, and it doesn’t appear to be due to a lucky appearance of several different mutations induced by some kind of environmental pressure. What they found was that “the presence of (probably) neutral mutations in one may enable other changes that predispose it to particular patterns of change.”
We often hear that evolution is not provable because you can’t test for it and repeat the tests to verify the accuracy. Yet in this experiment, scientists did just that: because they saved a sample of each population at each stage, they can “roll back the clock” and start the experiment over. By doing so, they were able to establish that three mutations had to occur for the “breakthrough” of citrate uptake in the E.coli, and it only happened in that population. On a verifiable, repeatable basis. This is exactly the mechanism predicted by evolutionary theory.
Myers addresses the Creationist claim that the experiment somehow supports the idea of “intelligent design” from a scientific standpoint. From my theological perspective, this experiment shows that evolution must be true or, as the only alternative, God is being held captive in a lab and being forced to exercise His creative powers on command.
