(From a post of mine on another forum)
Regarding the famous 'peppered moths' of England -- Creationists like to twist the truth about this moth, so I will go into both sides here:
(1) Creationist (
icr website)
This is taken directly from the web site:
Here's the well-told scenario. In the early 1800s, nearly all of the individual peppered moths (Biston betularia) were of a light grey, speckled color. Active mostly at night, they needed to hide by day from predatory birds. Since trees and rocks were typically covered with mottled light green, gray lichens, the moths were effectively camouflaged. A rare peppered moth exhibited a dark color and was easily seen by birds; thus they seldom survived. On average, over 98% of all the species were of the light variety, yet with both dark and light were of the same species and were fully interfertile.
Then came the industrial revolution and the air filled with soot, covering the trees and rocks with a toxic film, killing the lichens and darkening the trees. Soon the light variety of moth was easily seen while the darker were camouflaged. By the turn of the century, 98% of the moths were dark. When English medical doctor Bernard Kettlewell studied the phenomena in the 1950s, it became "Darwin's Missing Evidence"natural selection in action.
Remember that both varieties were present at the start, with the mix of genes producing lights favored over the mix of genes producing darks. As the environment changed, the dark variety had greater opportunity to pass on their genetic mix, and percentages changed. All the while, the two types were interfertile. No new genes were produced, and certainly no new species resulted. This is natural selection in action, but not evolution. Adaptation happens, but the changes are limited.
Please note that this is a creationist site and they have just said that "
This is natural selection in action, but not evolution." They go on to claim that this disproves evolution because the moth varieties are not now different species. But lets look at this claim:
............................natural selection.......evolution
theory tested.................yes.....................no...
theory validated..............yes.....................no...
theory invalidated.............no.....................no...
Because evolution is not tested in this scenario it cannot be used to invalidate the theory.
Please note how this
creationist website shows you exactly how the mechanism of color change in a population works. The moths did not decide to change color: there were existing genetic variations that made one population more able to survive under one condition and the other population more able to survive under a changed condition.
There are also some valid claims about some bad science done on this issue in early studies, and we will look at that issue below as well.
(2) Evolution and Natural Selection (
brown university website)
Note first off that this article refers to the two varieties of the moth:
- Biston betularia typica (the light color version) and
- Biston betularia carbonaria (the dark color version)
In the scientific name structure (for those unfamiliar with it) we have family (Biston) species (betularia) and variety (typica or carbonaria) designations.
An important distinction is made between 'species' and 'variety' and that is that 'varieties' can interbreed: when the genetic difference is great enough that no viable offspring are created then we would then have a different 'species' - this is the
scientific distinction. As we are not talking about species differentiation at this point in this scenario, the theory of evolution is not tested,
per se.
From
BIOLOGY by Miller & Levine, page 298:
"Kettlewell found that in unpolluted areas, more of his light-colored moths had survived. In soot-blacked areas, more of the dark-colored moths had survived. Thus Kettlewell showed that in each environment the moths that were better camoflaged had the higher survival rate. It was logical to conclude that when soot darkened the tree trunks in the area, natural selection caused the dark-colored moths to become more common. Today Kettlewell's work is considered to be a classic demonstration of natural selection in action."
Please note: "
a classic demonstration of natural selection in action." Both websites agree on this.
Now lets look at a scientific critique / review of the original / early studies:
... in 1998, Michael E. N. Majerus of the Department of Genetics at the University of Cambridge carefully re-examined Kettlewell's studies, as well as many others that have since appeared. What he reported, first of all, was that Kettlewell's experiments, indicating that moth survival depends upon color-related camoflage, were generally correct:
" Differential bird predation of the typica and carbonaria forms, in habitats affected by industrial pollution to different degrees, is the primary influence on the evolution of melanism in the peppered moth."
(P. 116, Melanism - Evolution in Action, M. E. N. Majerus, Oxford University Press, New York, 1998).
However, Majerus also discovered that many of Kettlewell's experiments didn't really test the elements of the story as well as they should have. For example, in testing how likely light and dark moths were to be eaten, he placed moths on the sides of tree trunks, a place where they rarely perch in nature. He also records how well camouflaged the moths seemed to be by visual inspection. This might have seemed like a good idea at the time, but since his work it has become clear that birds see ultraviolet much better than we do, and therefore what seems well-camouflaged to the human eye may not be to a bird. In addition, neither Kettlewell nor those who checked his work were able to compensate for the degree to which migration of moths from surrounding areas might have affected the actual numbers of light and dark moths he counted in various regions of the countryside.
These criticisms have led some critics of evolution to charge that the peppered moth story is "faked," or is "known to be wrong."
Neither is true. In fact, the basic elements of the peppered moth story are quite correct. The population of dark moths rose and fell in parallel to industrial pollution, and the percentage of dark moths in the population was clearly highest in regions of the countryside that were most polluted. As Majerus, the principal scientific critic of Kettlewell's work wrote, "My view of the rise and fall of the melanic form of the peppered moth is that differential bird predation in more or less polluted regions, together with migration, are primarily responsible, almost to the exclusion of other factors."
Thus the claims on the creationist site:
- "that Kettlewell's compelling argument has not been verified by other investigators" is outright wrong - it is verified by M. E. N. Majerus, in his book Melanism - Evolution in Action (Oxford University Press, New York, 1998).
- "Furthermore, we now know that neither dark nor light moths ever spend their days on exposed tree trunks or rocks as depicted in the famous textbook pictures. His original associates have even admitted that the photographs were faked, that the moths were glued onto the tree." And this issue has been discussed above and answered - yes some of the initial science was not correct (or done as properly as it would be done today), but the study is validated, the effect is confirmed.
Note that Majerus is described as "the principal scientific critic of Kettlewell's work" - and
he has validated and confirmed it. Also note that this website does not refer to this effect as 'proving evolution,' in fact it doesn't even discuss the theory of evolution or any relationship of it to the studies done on the moths.
POINTS IN AGREEMENT
- there were two varieties of the moth Biston betularia in England before the 'Industrial Revolution' and on average, over 98% of all the species were of the light variety,
- the 'Industrial Revolution' filled the air with soot, covering the trees and rocks with a toxic film, killing the lichens and darkening the trees
- soon the light variety of moth was easily seen while the darker were camouflaged.
- by the turn of the century, 98% of the moths were of the dark variety, and finally
- the change in populations was due to predation of the more visible variety
Thus, even creationists "would have to say it was nature itself" that "was the source of the change."
Enjoy.
we are limited in our ability to understand
by our ability to understand
Rebel
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