Take 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) by Dr. John Morris, President of ICR
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."
He goes on to imply that this disproves evolution because the moth varieties are not now different species. But lets look at this claim:
| natural selection | speciation
|
| theory tested | yes | no
|
| theory validated | yes | no
|
| theory invalidated | no | no
|
Because speciation is not tested in this scenario, the results 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 by Dr. Ken Miller, Professor of Biology, Brown University, RI, with additional material by Dr. Bruce Grant, Professor at the College of William and Mary.
We start with Ken Miller's website (
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 speciation part of 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."
Next, from Dr. Bruce Grant by linked article "
Fine Tuning the Peppered Moth Paradigm" (pdf):
In his 34 years of moth hunting, Majerus has discovered 47 peppered moths at rest by day in the wild. ... Majerus separates into categories the position on trees where the moths were located (trunk, trunk/branch joint, branches). While the trunk/branch joint was the most common site, his data indicate that the moths do not all rest in the same place. As Clarke et al. (1994) put it: "Moths habitually resting in only one place will be habitually sought there." ... In truth, we still don't know the natural hiding places of peppered moths.
Morph Specific Behavior. Kettlewell proposed that pale and melanic forms of peppered moths actively seek out
different resting sites. To test this idea, he put typicals and
carbonaria into a barrel lined with black and white strips of card, and he recorded where they had settled. (The moths are active at night, but remain motionless, unless disturbed, during the day.) From these "barrel" experiments, Kettlewell (1955b) reported morph specific behaviors:
carbonaria tended to settle on black, and the typicals tended to settle on white. Kettlewell suggested that the moths accomplish this by comparing the darkness of their body scales to the surface reflectance of the immediately available substrates and that they come to rest where the contrast between the scales and the substrate is least "conflicting."
Despite design problems, Kettlewell’s predation experiments are still instructive. He used the same procedures in two distinctly different places, a habitat disturbed by pollution and an unpolluted habitat, and he got complementary results. His data, in both directions, were in complete accord with the directions predicted by the incidence of melanism in the regions. So, if he was wrong to use the trunks of trees in Birmingham, he was consistently wrong to use the trunks of trees in Dorset. If he was wrong to release the moths during the daylight hours in Birmingham, he was consistently wrong to release the moths at the same time in Dorset. His data, however, show that the variable of regional pollution made a significant difference as to which phenotypes of the moths better survived the conditions imposed by the experiments.
Kettlewell's aren't the only experiments that show this. Majerus recounts five other studies, using variously modified experimental designs, that corroborate fitness differences between the morphs in polluted and unpolluted regions. He also reviews some exceptions. Hindsight has enabled us to find fault with all of these experiments to varying degrees and has helped us to suggest future work. It is not true, however, that these experiments are so seriously flawed that their conclusions are invalid. The conclusion that conspicuous moths are more readily eaten by birds than are inconspicuous moths has been repeatedly confirmed. The findings from the grand bulk of the predation experiments are in qualitative agreement with the direction of changes in melanic frequencies documented among geographically separated populations of peppered moths.
Again, note "
While the trunk/branch joint was the most common site" showing that moths do, in fact, rest on portions of the tree trunks. While we cannot say what actual proportion of time is spent in various locations at various times of the day and night, it is
absolutely false to claim that peppered moths
never rest on the bark of the trees or other locations where the camouflage effect would come into action. Nor can it be argued that the moths are not cognizant at some level of the background they chose to rest on. Focusing on just the main trunk or rocks of the experiments done by Kettlewell is a strawman argument as it does not represent the range of possible resting sites that do involve contrasting visibility or on the other experiments he conducted that showed a preference for camouflaged resting sites, nor does it address the issue of the moths being glued in specific sites to test the differential predation of the insects by birds or that other experiments that were conducted with released moths. Kettlewell's experiments determined (a) that peppered moths apparently selected backgrounds for resting sites that matched their coloring and (b) that birds differentially found and ate moths that were more conspicuous by lack of camouflage first and (c) that there were in fact population shifts between polluted (dark) areas and non-polluted (light) areas.
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) and by others that followed Kettlewell.
- "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 done as properly as it would be done today, but the different studies isolated different aspects of the situation, the overall conclusion has been validated, and the effect is confirmed by others.
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, if not more (the dark variety was first noticed in the early 1800's)
- 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.
And thus we see agreement that this example is about the Natural Selection part of evolution, and not about speciation, and further that it cannot be about speciation because it is talking about the relative size of populations of two varieties of the same species of moth.
The website by Ken Miller ends with some recommended Background Reading:
The web page of
Bruce Grant, Professor at the College of William and Mary, and especially his paper, "
Fine Tuning the Peppered Moth Paradigm." (pdf)
Prof. Grant has also written to rebut charges that the Peppered moth story is fraudulent: "
Charges of Fraud Misleading."
Also: William Majerus' book "
Melanism - Evolution in Action" can be found on many library shelves. He has a new book about to be published: "
Moths."
Enjoy.
Note to ADMIN:
I know there is another thread on the peppered moths, but it relates more to Wells and his "icons" issue. This one addresses creationist implications of lies and fraud, an issue recently asserted by randman, and thus it is topical once more. Let's start clean and not involve Wells in this issue here.
Either {Biological Evolution} or {is it Science} would be okay.
Edited by RAZD, : tyop Maherus fixed
Edited by RAZD, : fixed ICR link
Edited by RAZD, : fixed Ken Miller link
Edited by RAZD, : replaced text block with table
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