Britain’s peppered moth has long been an evolution icon. This month, a new genetic discovery renews the spotlight on the moth. “Researchers from the University of Liverpool,” reports ScienceDaily, “have identified and dated the genetic mutation that gave rise to the black form of the peppered moth, which spread rapidly during Britain’s industrial revolution. The new findings solve a crucial missing piece of the puzzle in this iconic textbook example of evolution by natural selection.”
Peppered moths are notable for their unique speckled range of colors from light, shades of gray, to nearly black. The dark moths are also known as melanics or carbonaria. ScienceDaily’s crucial missing piece evidence, the “jumping gene,” was published this month in the prestigious journal Nature. “From time to time,” however, according to Jerry Coyne, a University of Chicago evolution scientist, “evolutionists re-examine a classical experimental study and find, to their horror, that it is flawed.”
Enshrined as prima facia scientific evidence of Charles Darwin‘s theory of natural selection, the peppered moth emerged as an icon of evolution ― but not until the mid-20th century. What is often overlooked is the fact that Darwin’s theory of natural selection was speculation – not scientifically tested evidence. In Chapter VI entitled “Illustrations of the Action of Natural Selection” in The Origin of Species, Darwin makes this point clear ―
“In order to make it clear how, as I believe, natural selection acts, I must beg permission to give one or two imaginary illustrations.”
Not until 1898 was Darwin’s theory of natural selection tested with using measurable evidence. After a severe snowstorm in Providence, Rhode Island, biologist Hermon Bumpus (pictured right) found a large number of English sparrows close to death. Bumpus captured and transferred 136 of the sparrows back to his laboratory, where nearly half of them died.
In measuring the living and the dead, the survivors tended to be shorter and lighter-weight males. Bumpus concluded that the storm had taken a greater toll on sparrows that deviated the most from the “ideal type.” This pattern of differential survival, Bumpus claimed, was due to the actions of natural selection. For his work, Bumpus was eventually appointed director of the American Museum of Natural History in 1906.
What would become the epic 20th century evolution icon, however, did not emerge on the horizon until British geneticist Bernard Kettlewell ventured into the British heartland inhabited by peppered moths, Biston betularia―more than 50 years later. The epicenter of British textile manufacturing powered by coal during the 18th century Industrial Revolution was largely centered in Manchester and Birmingham located in the central region.
By the 19th century, the emergence of these great industrial cities had covered the area in a blanket of coal dust. The buildings and vegetation became increasingly dark. Areas once inhabited by light colored moths on lighter colored vegetation, were now largely populated by dark colored moths on darkened vegetation. The transformation is known as industrial melanism.
With a government grant to study industrial pollution in general and the peppered moth in particular, Kettlewell began to collect data from the central England in three major surveys between 1952 and 1972. During this period, however, no measurable changes were observed.
Not dissuaded by the lack of note-worthy findings, Kettlewell designed a field experiment to test Darwin’s theory of natural selection. After breeding populations of light- and dark-peppered moths in his laboratory, the wings were tagged with a paint-dot for tracking.
Kettlewell released the marked moths for the experiment from both groups into two types of wooded areas in central England: coal polluted and coal unpolluted areas. On the night following the release of the moths, traps were set.
In the polluted areas, of the 447 dark-colored moths that were marked and released, 28% were trapped, while only 13% of the 137 light-colored moths that were marked and released were trapped. Kettlewell concluded that predatory birds selected the more visible light-colored moths on the pollution-darkened tree trunks, leaving more dark-colored variety to survive and reproduce.
The same experiment was repeated in the unpolluted wooded areas surrounding the county of Dorset, located in the southwest England distanced from the industrial central areas. On the following night, 13% of the light moths and only 6% of the dark moths were trapped. In the words of Kettlewell, the evidence from the peppered moth is –
“… the most striking evolutionary change ever actually witnessed in any organism.”
“… the clearest case in which a conspicuous evolutionary process has actually been observed.”
Kettlewell declared that the “birds act as selective agents, as postulated by [Darwin’s] evolutionary theory” and published an article in Scientific American in 1959 entitled “Darwin’s Missing Evidence.” British geneticist P. M. Sheppard called the phenomenon
“… the most spectacular evolutionary change ever witnessed and recorded by man.”
These tagged British peppered moths quickly emerged as a textbook evolution icon classic. By the early 1980’s, however, biologists began uncovering fundamental problems with Kettlewell’s naïvely conceived experiment.
In the wake of antipollution legislation in the 1950’s the darkening effects of industrialization began to gradually reverse. New field studies demonstrated that the proportion of light-peppered moths to be increasing (see graph), dissipating the effects of more than 200 years of coal burning while the proportion of dark melanic moths decreased to the numbers previously recorded by Moses Harris in 1776.
To save the dying icon, during the 1970s, several investigators attempted to retrace Kettlewell’s experiment. Liverpool biologist Jim Bishop, however, failed to reproduce Kettlewell’s premise that light-peppered moths predominate in unpolluted areas.
D. R. Lees and E. R. Creed later demonstrated that in the little-polluted areas of East England, where the light-colored moths were considered better camouflaged than the dark colored moths according to Kettlewell’s theory, the dark-colored moths were found to account for 80% of the moths of the total peppered moth population. The investigators concluded:
“Either the predation experiments and tests of conspicuousness to humans are misleading, or some factor or factors in addition to selective predation are responsible for maintaining the high melanic frequencies.”
At best, Kettlewell’s peppered moths serve as an example of adaptation–not biological evolution. Contrary to Kettlewell’s hopeful conviction of observing evolution-in-action, no new species has ever or since emerged.
In 1999, The Daily Telegraph ran Robert Matthews story “Scientists Pick Holes in Darwin Moth Theory” noting
“scientists admit they do not know the real explanation for the fate of Biston betularia.”
The Washington Times (1999) published Larry Witham’s article –
“Darwinism icons disputed: Biologists discount moth study.”
The New York Times. (2002) published Nicholas Wade’s paper
“Staple of Evolutionary Teaching May Not Be Textbook Case.”
University of Chicago evolutionary biologist, Jerry A. Coyne, (pictured left) published an important observation that Kettlewell overlooked in the journal Nature (1998): peppered moths do not rest on tree trunks which –
“alone invalidates Kettlewell’s release-and-recapture experiments, as moths were released by placing them directly onto tree trunks.”
The “prize horse in our stable of examples” of evolution, Coyne explained, “is in bad shape.” In the words of Japanese biologist Atuhiro Sibatani,
“… the story of industrial melanism should be shelved.”
“We contend… that there is little persuasive evidence, in the form of rigorous and replicated observations and experiments, to support this explanation [natural selection].”
The vast majority of biology textbooks covering evolution, however, still uses the peppered moth as the classic example of natural selection in action. Bemoaning the continued use of what he termed “misinformation,” even Stephen Gould, (pictured right) opined –
“Once ensconced in textbooks, misinformation becomes cocooned and effectively permanent, because … textbooks copy from previous texts.”
The University of Liverpool of report of solving “a crucial missing piece of the puzzle in this iconic textbook example of evolution by natural selection” reconfirms Gould’s fear – evolution industry’s addiction to the resurrection of another dead evolution icon.
Since this rise and fall “black and white story” ends without any evidence for the emergence of a new species, the credibility of Moses’ Genesis account – “kind after kind” – once again stands with the scientific evidence.
In the words of the father of modern physics, Galilei Galileo,
“God is known by nature in his works, and by doctrine in his revealed word.”
Evolution, once a theory in crisis, is now in crisis without even a cohesive unifying theory. Biological evolution exists only as a philosophy–not as a scientific fact.