There’s a really interesting article in last week’s NY Times magazine about global warming and the spread of weeds. There was, however, one jarring note, and it had to do with an incorrect definition of natural selection (italics mine):
“There’s no such thing as natural selection,” Ziska confides. He is not, he hastens to explain, a creationist. He is merely pointing out that the original 19th-century view of evolution, the one presented by Charles Darwin and Alfred Wallace, is obsolete. Their model presented evolution as a process taking place in a nature independent of human interference. That is almost never the situation today — even at sea, where less than 4 percent of the oceans remain unaffected by human activity, according to a recent article in the journal Science.
I don’t mean to pick on Ziska–he’s doing excellent and important work–but that’s not correct, at least for the last few decades. Artificial selection occurs when the fitness criterion–that is, what trait or phenotype will have higher survivability or reproductive output–is directly chosen by the experimenter. In the case of the weeds, if we were delibrately trying to grow better weeds–that is, mowing down rice biovars that aren’t sufficiently ‘weedy’–that is artificial selection. Simply changing the environment such that weedy biovars will do better is natural selection because we are not specifically trying to enrich for rice that have the trait of ‘weedy-ness.’
Keep in mind that one can use natural selection for very applied purposes, and the boundaries will get fuzzy, but in the case of global warming, this is clearly natural selection. Besides, in a materialist sense, we are just another species of critter.