Oct 11 2009
Most of you are probably familiar with the case of the peppered moth. In it’s original form, the moth was lighter in color. Enter the industrial revolution and the discoloration of surfaces, such as tree trunks, due to soot in the air. Over the course of moth generations, they took on a darker coloration. Those that blended with their environment better avoided predation and survived to reproduce. Dark color-genes were naturally selected for, you could say. Though there wasn’t an agent doing the selecting, nor was there a greater purpose to the selection.
A similar case has been discovered and studied. This time it was not peppered moths in England, but deer mice Nebraska. And the species did not darken in color, but lighten. Why? During the last ice age, “glaciers deposited sand dunes atop what had been much darker soil.”
For a mouse, as with a moth, standing out is not a good thing. Although hawks and other predators would differ in their preference for the color of their dinner.
How do we know these mice were once darker in color? Because the darker variety still exists. One might argue that the darker is a transitional variant of sorts. At least were the sand dune mice to eventually become a completely isolated and separate breeding population that eventually didn’t recognize the darker mice as potential mates. Call it evolution in action. And it’s happening right under our noses.
Here a little more info from the source article:
This and other evidence, including much greater genetic uniformity among pale mutants than their dark wildtype cousins, suggests this mutation is a relatively recent development, likely arising shortly after the formation of the Sand Hills in north-central Nebraska.
By mating light Sand Hills mice and dark mice found outside the Sand Hills, Linnen and Hoekstra determined that the light coloration seen in Agouti mutants is genetically dominant to the darker coats seen among wildtype mice.
One last point. During a recent Colbert Report episode, Richard Dawkins told the host of the show that any purpose to life is a human purpose. We create any purpose perceived. And I agree with that. Dawkins also said that, yes, evolution is random. But this point I wonder about. Hear me out.
In the case of the mice, for instance, genetic mutation responsible for the change in deer mice coloration. I wonder if this type of mutation is completely random. Could there be some sort of epigenetic input involved? Biologists have recently come to understand that experiences can turn off and on already existing genes. Nurture triggers nature. Can some types of experience likewise make some genes more likely to mutate than others? Has the differing visual input (experience) of the deer mice, triggered a greater propensity for it to undergo genetic change (nature) in it’s fur-coloring genes? I wouldn’t be surprise if in the future we discover that much of randomness to evolution is actually more of a reflection of our ignorance than anything else. Of course, the opposite of random is not purposefully determined.