Wells' Icons of Evolution - Peppered Moths

Cromwell, I am unsure exactly what point you are making. You seem to be saying that there is not enough time for the changes to occur.However, they did. This is unquestioned. From here, the first recorded carbonaria sighting was 1848. By 1895 98% of the peppered moths in Manchester wer of this form, but within 80 years or so, the proportion had dropped dramatically: to such an extent that extinction is predicted in the next few decades. Note that in non-industrialised areas the typica form remained overwhelmingly dominant.Regardless of the detailed explanation this is a classic example of Natural Selection in action, unless of course you are proposing some form od Non-Natural Selection. In which case what?However, there are some recently voiced problems with some of the classical solutions:

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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 comoflaged 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-camoflaged 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.

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These criticisms have led some critics of evolution to charge that the peppered moth story is "faked," or is "known to be wrong."

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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 primarilty responsible, almost to the exclusion of other factors." (p. 155).

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So, what's going on here?

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Well, the best way to put it is that what we are seeing is the scientific process at its best. Majerus and other ecologists have carefully examined the details of Kettlewell's work and found them to be lacking. As Majerus explains, to be absolutely certain of exactly how natural selection produced the rise and fall of the carbonaria form, we need better experiments to show that birds (in a natural environment) really do respond to camoflage in the ways we have presumed, that the primary reason the dark moths did better in polluted areas was because of camoflage (and not other factors like behavior), and that migration rates of moths from the surrounding countryside are not so great that they overwhelm the influence of selection in local regions by birds. Until these studies are done, the peppered moth story will be incomplete. Not wrong, but incomplete.

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What we do know is that the rise and fall of dark-colored moths, a phenomenon known as "industrial melanism," remains a striking and persuasive example of natural selection in action. What we have to be cautious about is attributing 100% of the work of natural selection in this case to the camoflage of the moths and their direct visibility to birds.

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As can be seen from this quote, the problem is with the details, not the substance of the story.

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Cromwell,I am unsure exactly what point you are making.You seem to be saying that there is not enough time for the changes to occur.

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Not enough time for the changes to occur by the definition of natural selection because of cryptic camouflage predation.Peppered moths resting on trees and becoming the victims of predation are extremely rare,given the observations by Majerus.Changes in a period of 50 years can not be made to fit within such a time period,as the predation in the wild is almost non existant.Not enough "material" and causes to give rise to natural selection taking place.

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Nonsense. Evolutionary changes have been observed over much smaller timescales. Look at the work on Darwin's Finches by Peter and Rosemary Grant. They clearly demonstrated quite rapid changes over quite short times in response to environmental changes. However, normally, the environment changes around a norm, so, averaged over the long-term, no change is observed.

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If you read my first thread,you will see that i don't deny that something has caused the change over of dominant variants.This fact is undeniable.Wells points to it being something yet undiscovered,but due to pollutants.I am saying that it is not happening through the mechanism of natural selection.I am not saying its a fake.but i'm merely saying that the data does not prove that it can be natural selection and that other contributory factors have not been considered.

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What you have quoted above illustrates the problem.Its not concrete.How birds see the prey is also something else to take into consideration.What are your views on these matters?

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But, I repeat if natural selection regardless of cause is not happening, what is? Increasingly. this looks like an argument from personal incredulity. Predation is so central to evoilutionary pressure that, at first sight, it would be the obvious cause of selection. Even with the doubts expressed recently (which, let it be noted, does not include the infamous photographs, which have always been know to be illustrative of the camoflage effect of the two type of colouration, although, admittedly, some secondary sources have omitted this information), predator pressure is still considered the most likely cause, but more work needs to be done to eastablish this.