The peppered moth story (also called "Industrial Melanism") is presented as a classic case of what evolution can do. But is it? The textbook account goes like this: Peppered moths (Bison betularia) come in two forms, light ("typical") and dark ("melanic"). Before the industrial revolution in the middle 1800's, melanic moths were considered to have been rare. (Fig. 1) During the industrial revolution, air pollution on an incredible scale turned everything downwind of industrial Britain soot black. This included the trees where the moths were purported to land. As a result, so the story goes, of selective predation by birds on the lighter moths resting on the now blackened trees, the darker melanic form came to dominate. When legislation was introduced to control pollution a century later, the trees gradually recovered their lighter, lichen-covered trunks, the darker moths were more readily captured by predators, and the lighter typical forms again came to dominate the moth population. The shift in population densities of the two forms was attributed to natural selection. The lighter typical forms were well camouflaged on the lighter lichen-covered tree trunks upon which they rested in the pre-industrial era. The darker melanic forms were better suited to survive on the soot-darkened trunks of the industrial era. It was natural selection that resulted in the shift in population densities. Presumably, a return to the pre-1950's level of air pollution, would once again result in a shift toward the darker morphotype.
The variation in the moth colors was first recognized in the mid 1800's, but there was no concensus about its meaning. Some attributed it to the effects of pollution, others ascribed it to normal variation within the population. By the 1920s, it was well known that the moths had undergone a shift in color in some regions of the country from predominantly typical to predominantly melanic. A British scientist, J. W. H. Harrison, undertook to understand the change through experimentation. He was of the opinion that mutations were responsible for the variation, and that these mutations occurred in each differing individual. He further attributed the mutations to pollution. To test his hypothesis, he fed the larva of the peppered moth leaves that had been coated with soot. He reported an increase in the melanic forms among the offspring fed the soot-treated leaves. He published his results in the British journal Nature in 1927.
This appeared to be a substantiation of the role of mutation in industrial melanism. Because of the profound importance of his findings, other scientists attempted to repeat his findings, but with little success. Because Harrison was highly respected, other scientists concluded there was an unknown factor influencing the outcome of their experiments that prevented them from duplicating Harrison's work. However, other scientists who did not particularly agree with Harrison's theory, questioned his explanation and his data. But little more was done for another 20 years.
This story was next joined by one Bernard Kettlewell, a British physician with a lifelong interest in the lepidoptera. Kettlewell developed an elaborate hypothesis to explain what he saw to be a significant shift in the population of peppered moths from the predominantly darker form to the typical. He performed a series of elegant experiments during the years from 1952 - 1957 to test this theory. He reared both types of moths and released carefully marked moths early in the morning. Then during the day he would attempt to ascertain their fate in both polluted woods and non-polluted woods. He would place moths on tree trunks of various shades, and station an observer nearby under a robe with a camera to attempt to record the predation by birds. His results were widely acclaimed both in the scientific community and by the general public as being the most salient example of natural selection and Darwinian evolution.
The story began to unravel in the 1970's, however, as further study revealed the distribution of moths did not fit various predictions. For example, in Britain, the darker forms were found to be prevalent in some woodlands where the trees had lighter bark, and the lighter moths returned to areas freed from pollution before the lichens that lightened the bark had begun to repopulate the trunks. In other areas of the world where the moths were found, changes in the frequency of the lighter and darker morphs were not correlated with any change in the trees.
The most devastating discovery came fairly recently when suspicions of long duration led to a careful study of the behavior of the moths. These studies demonstrated that the moths do not normally rest on tree trunks at all! Moths generally, and peppered moths in particular, are active at night. The moths were found to resort normally to roosts high up in the tops of trees, on the underside of small branches during the daytime. Kettlewell's studies involved release of moths raised in captivity early in the morning when they would be torpid and would generally remain where he placed them. Thus his belief that the moths were being selected from the trunks of trees by birds led him to artificially place them there. In addition, we are told that "Special sets of moths were settled on tree trunks within reach of my camera, which I could aim from my canvas hide at whatever bird would appear." Niko Tinbergen (quoted from Kettlewell's obituary). It now appears that Kettlewell's experiments were not about natural selection at all, but about a very contrived artificial situation which may tell us nothing whatsoever about how things work in nature.
Photographs of moths resting on tree trunks were, up until recently, found in every general biology textbook. Even this simplest of examples of what evolution is purported to do, this celebrated test case for real evolution in action, is, shamefully, a misrepresentation of nature. The moths shown in the photographs were invariably either dead specimens glued to the tree, or inactive moths which have been carefully placed there. This situation is now being more widely recognized in the literature (see, for example, Journal of Heredity 89:465 and Evolutionary Biology 30:299)."
As an interventionist, I have no difficulty wth the peppered moth story if it were true. The shifting of the frequency of alleles, and a whole lot more change must have occurred in the course of life on earth. But what is especially troubling is that these stories, known to be false since the late 1980's at least, persisted in the textbooks of biology 20 years after the true nature of the story was known, as illustrations of the process of evolution. Not just the peppered moth story, but the Haeckelian embryo falsifications and the Miller-Urey experiments are represented as the highest examples of what naturalism can do. This is sad. Darwinists are apparently so desperate for confirmatory examples that they have to hold on to and promote these instances as the very best examples of evolutionary science, knowing full well that they distort truth.
2010 Arthur V. Chadwick, Ph.D.