It makes me absolutely livid when reporters take a common instance of natural selection and act like it proves Darwin correct on all counts. In this story, called “Darwin Got it Right,” scientists noted that the introduction of a predator made a prey species “evolve” more than once in a year.

From the story:

“In the first six months the brown arole, Anolis sagrie, developed longer legs so that it could outrun its predator, Leiocephalus carinatus.

“Over the second six-month period the arole changed its behaviour so that it spent far less time on the ground and longer on branches and plant stems.”

First of all, they claim the changes happened “within a single generation.” Darwinian evolution is a process of birth as well as death, so one generation is the very minimum it can take to occur, at least at the genetic level. All the scientist is saying is that predators killed all the lizards with less-than-optimal features, making the “average” limb length change — until the next generation is born, we won’t even know how many of the changes have been passed on genetically. For example, many of the long-leg lizards probably have some short-leg recessive genes. The species has “developed” nothing.

Yes, evolution happens faster in large-scale massacres occuring under unnatural circumstances, so the newborns will likely confirm their suspicions, but what’s happened so far isn’t even one complete cycle of Darwinian evolution. It’s amusing to have a big-name paper run a story about evolution that doesn’t even mention the reproduction half of the theory.

On a side note, a change in behavior is adaptation, not evolution, if it happens “within” a generation.

Second, no serious person — and I mean no serious person — disputes natural selection. If you kill all the dark-colored moths, future generations will have lighter tones. To not believe in natural selection, you’d have to not believe in genes. The debate, and I won’t get into it here, is whether random genetic mutations can account for each and every development between single-cell organisms and human beings.

Finally, they use the study as evidence that evolution can happen incredibly quickly. Sure, but like I said, only when incredibly drastic things happen. This sort of situation, where tons of predators at once randomly descend on a previously tranquil species, doesn’t happen in nature too much. That’s why they had to set it up instead of observing such a scenario in the real world.

Robert VerBruggen blogs at http://robertsrationale.blogspot.com.