Moth study backs classic ‘test case’ for Darwin’s theory

Moth study backs classic ‘test case’ for Darwin’s theory – Independent Online Edition > Sci_Tech

The news article reports that Michael Majerus is now presenting data from his own seven-year study of peppered moths. His study site: his backyard in Cambridge, UK. His methodology: fix all the issues that have been raised about Kettlewell’s research back in the 1950s, including those raised by the professionally ignorant crowd of evolution deniers and crypto-creationists. The results: birds are the major selective pressure on color morphs of the peppered moth, Biston betularia.

Peppered moths come in two color morphs, the “peppered” variety that is a variegated gray brown with black speckles, and a dark form, or “carbonaria” morph, that is a solid dark gray to black color. Before the Industrial Revolution in England, the carbonaria forms were known, but were very rare. During the Industrial Revolution, so much soot was released from the burning of coal and wood for fuel for steam engines that there was widespread pollution of exposed surfaces. This included the trees in which peppered moths spend time. As this progressed, people noticed that the black or “carbonaria” form of the peppered moth was no longer rare; it was, in fact, the most common color morph around. When the pollution from industrial sources abated and trees returned to being tree-colored, there was once again a shift in color morph frequency, and the “peppered” form once again became the predominant one seen. Or, I should say, generally unseen, for the primary issue here is crypsis, the ability of an organism to go about its business unobserved and therefore not pounced upon by hungry predators. The peppered color morph does a good job of blending in with a background of unpolluted bark. The carbonaria or dark color morph does a good job of blending in with a background of soot on bark (or, likely, any soot-covered surface). But each color morph is stunningly un-cryptic when on the opposite background: the carbonaria form sticks out when on unpolluted bark, and the peppered form is far lighter in color than the bark of a soot-covered tree.

Bernard Kettlewell did research on peppered moths in the 1950s, testing the difference in survival of these color morphs in polluted and unpolluted forests. He used a release and recapture method to test differential predation. And Kettlewell’s experiments famously supported bird predation as a primary cause of natural selection acting on these populations. Birds, it seemed, also went for the out-of-place moths, the ones whose color scheme was at a mismatch with the state of the tree bark in the area.

As Majerus notes,

“The peppered moth story is easy to understand, because it involves things that we are familiar with: vision and predation and birds and moths and pollution and camouflage and lunch and death,” he said. “That is why the anti-evolution lobby attacks the peppered moth story. They are frightened that too many people will be able to understand.”

Bravo, Michael Majerus. That captures the essence of the opposition in a nutshell.

One often hears evolution deniers saying that they don’t have an issue with “microevolution”. One can discover just how much stock to put into that by looking at how much effort they put into disputing or dismissing examples of within-species evolution. The result is that they put a lot of effort into gainsaying microevolutionary examples, and thus their assertions to the contrary are falsehoods. All that remains to determine is whether those are deliberate falsehoods or not. Given the incredibly poor background evolution deniers generally have in the fields they criticize, it certainly is the case that a great many of the followers of the antievolution movement pass along those falsehoods because they put their trust in the professional evolution deniers, who tell them that these are good arguments to make. The professionals, though, don’t have that easy out. They have represented themselves as authorities on the issues, and yet they are still passing falsehoods.

Take, for instance, Dr. Dr. John C. “Jonathan” Wells, who made a point of pursuing his second doctorate for the express purpose of better being able to pursue “destroying Darwinism” for Rev. Sun Myung Moon. His field for his first doctorate was some form religious studies at Yale, but his second was developmental biology at U.C. Berkeley. In 1999, Wells published a book, “Icons of Evolution”, which features a chapter casting doubt on peppered moth research, saying that it the mechanism of natural selection was not properly established as the cause of observed changes in frequency of color morphs in the population. In online discussions, he accused the research — and the presentation of that research in textbooks — as being “fraud, fraud, fraud”. Along the way, Wells claimed that peppered moths never rest on tree trunks (Majerus has data showing that they are observed on tree trunks about a quarter of the time; certainly not their very favorite place to be, but not out of bounds for where they can be seen), and that all photographs of peppered moths on tree trunks were “faked” (Majerus also has photographs of live, unrestrained specimens on tree trunks, plus there is the point that the purpose of the photographs of pinned moths is not to represent a “typical resting place”, but to illustrate crypsis, for which any sort of moth, pinned or unpinned, serves equally well).

Now that Majerus is weighing in that the conclusions of the original research are supported by his recent experiments, one can see the casual backpedaling on the part of evolution deniers. Despite the fact that they were, quite recently, telling us that this example of microevolution was in trouble and that we should downgrade our opinion of any textbook that used the peppered moth research in a positive light as an example of natural selection observed in action, now they are trying to shift the goalposts, saying that there was no speciation involved in these populations. Well, duh. Speciation would be a macroevolutionary event, but that was never a claim made with respect to the peppered moths. Evolution deniers wanted to deny that there were any appreciable instances of observed changes in traits happening due to natural selection. They put a lot of effort into trying to smear Bernard Kettlewell’s reputation, including a book-length character assassination by Judith Hooper (but don’t expect to hear a word about that in the “Expelled” film coming up; there is a word for that behavior, and it is hypocrisy) and cast doubt on peppered moths as an example of natural selection in action. But they just cannot bring themselves to admit error here.

Links: Alan Gishlick covers peppered moths for NCSE

Mike Dunford responds to Jonathan Wells’s new attack on peppered moths