Ohio Moth Myths

The Ohio year 10 high school lesson plan “Critical Analysis of Evolution” was recently accepted amid a great deal of controversy. Detailed criticisms of the lesson plan as originally proposed are here:

http://ecology.cwru.edu/ohioscience/Controversy_Guide.html http://ecology.cwru.edu/ohioscience/lesson_plan_critique.htm http://ecology.cwru.edu/ohioscience/References_analysis.html http://ecology.cwru.edu/ohioscience/Web_site_analysis.html

One of the key criticisms was thta the lesson plan included non-scientific material from creationist and anti-evolutionary sources. The lesson plan was revised, and the proponents claim that the revised plan is good science, and does not contain either creationism or “intelligent design”. However, these claims are incorrect, as I will show with an analysis of the peppered moth example.

See the following link for the Ohio “Critical Analysis of Evolution”lesson plan as passed:


Here’s the objectives from the revised lesson plan to allow us to focus on what the lesson is supposed to achieve, and to see how the current plan is riddled with creationist and ID misinformation.

Lesson Summary:

This lesson allows students to critically analyse five different aspects of evolutionary theory. As new scientific data emerge, scientists’ understandings of the natural world may become enhanced, modified or even changed all together.

Aspect 4: Peppered Moths (Biston betularia)

To start with, Peppered moths are not an aspect of evolutionary theory, they are used as an illustration of natural selection (which is one of the mechanisms of evolution), while this may seem pedantic, this example shows extereme confusion between a basic element of a theory, and experimental conformation of that element (in the same way the observed shift of stars photographed during a solar eclipse [a very controversial finding at the time] supports an aspect of relativity theory but is not itself an aspect of relativity theory).

My comments are interleaved with the text of the lesson plan.

Brief Challenging Sample Answer: <blockquote>English (And US, and European - Ian) peppered moths show that environmental changes can produce microevolutionary changes within a population.</blockquote>

First problem, this has nothing to do with the peppered moth example in relation to scientists changing understanding over time, the whole point of the lesson plan. The question started off in the 1940’s to 1950’s as “were the changes in the population due to natural selection” and by the 90’s became “what is the quantitative contribution of various selective agents to the change in the population”.<blockquote>They do not show that natural selection can produce major new features or forms of life, or a new species for that matter - i.e., macroevolutionary changes.</blockquote>This is a standard creationist statement, and way be found on a number of creationist web sites. It is not a statement made by scientists. The purpose of Kettlewell’s and other experiments was to determine if the changes in peppered moth genotypes was due to natural selection, these experiments were not intended to look at speciation or other aspects of evolutionary theory. This part of the “Challenging sample answer” is irrelevant to the lesson objectives.<blockquote>From the beginning of the industrial revolution, English peppered moths came in both light and dark varieties.</blockquote>The first known melanic (dark colored) mutant was found in 1848, well after the start of the industrial revolution, in Manchester, England. By 1895 98% of the peppered moths in that area were dark. The pattern of spread of the melanic form is consistent with the spread of mutation that first occurred around Manchester. This statement is simply wrong, but is another myth perpetuated by creationist writings.<blockquote>After the pollution decreased, dark and light varieties still existed.</blockquote>As would be expected, under standard evolutionary theory. This appalling ignorant sentence is also found in creationist writing.<blockquote>All that changed during this time was the relative proportion of the two traits within the population.</blockquote>Which is the standard definition of evolution. Populations of peppered moths underwent a dramatic reversal from 99-100% dark moths to below 10% in around 40 years, paralleling the rise of the dark form. Given the measured selection co-efficents for light and dark forms in the current environment, it would be expected that a few more decades will pass before the melanic form is extinct based on standard mathematical models of natural selection. An the fit of the actual fall in numbers to the predicted fall in numbers is very good.<blockquote>No new features and no new species emerged.</blockquote>Which was not the point of the peppered moth story, it was demonstrating natural selection in the wild. Again, this is a standard creationist statement, and is irrelevant to the lesson plans objectives.<blockquote>In addition, recent scientific articles have questioned the factual basis of the study performed during the 1950s.</blockquote>No, they haven’t,

a) there were several studies between the 1950’ s and 1970’s which all gave the same results. b) Recent studies have raised questions about the values of selection co-efficients derived from experimental studies. Much in the same way that modern studies have improved estimates of the speed of light. The factual basis of these several studies is still sound. Studies done in the 80’s re-evaluating the older studies can to the same conclusions. In all, over 20 independent studies have confirmed the orginal findings.<blockquote>Scientists have learned that peppered moths do not actually rest on tree trunks.</blockquote>This is in fact completely untrue, as a perusal of the actual literature will show. eg see Howlett, RJ and Majerus, MEN. (1987). The understanding of industrial melanism in the Peppered moth (Biston betularia) (Lepidoptera: Geometridae). Biol. J. Linn. Soc., 30:31-44. or Majerus, MEN. (1998) Melanism: evolution in action. Oxford University Press, Oxford. Chapters 5 and 6. This point is directly out of Well’s discredited book “Icons of evolution”, even though the actual book has been removed from the reading list. I believe that a statement that “moths do not rest on tree trunks” was false was submitted to the Ohio board of eduction by a group of the top peppered moth researchers.<blockquote>This has raised questions about whether color changes in the moth population were actually caused by differences in exposure to predatory birds.</blockquote>Not amongst scientists, who have access to the facts. The key question amongst scientists at present is not WHETHER bird predation was involved, but to get a quantitative figure for the amount of differential bird predation.

[end of Brief Challenging Sample Answer:]

The peppered moth example IS an example where scientists critically re-evaluated data. The key issues were how adequate models of selection were and how quantitative assessment of selection intensity was made. These are rather technical subjects, and not easy for middle high school students to evaluate even when given the actual papers for this discussion rather than the highly inadequate reading list suggested (only two references, on a popular article, the other a specialist journal article form about the middle of the investigation of the peppered moth story, which misses out on most of the key papers in the discussion).

In terms of the lesson plan, the “challenging sample answer” fails as it does not “Describe how scientists continue to investigate and critically analyse aspects of evolutionary theory” because it has no actual relation to the real analysis of the peppered moth example, and drags in irrelevant red herrings direct from creationist and intelligent design literature. The supporting sample answer is poorly organised and fails to clearly state what it is supporting.

In terms of the work sheet “Write a brief summary of what you have read and discovered regarding your particular aspect and how it challenges evolutionary theory.” the “challenging sample answer” again has no relationship to the peppered moth example.

In conclusion the sample exercise grossly misrepresents how scientists critically evaluated the peppered moth experiments, provides inadequate resources to even begin to evaluate this rather advanced and technical issue, and the sample answers, especially the “Challenging sample answer” betray a lack of understanding of basic evolutionary biology, standard creationist misunderstandings, as well as not even addressing the goals of the sample lesson plan. This is just one example of how this lesson plan is riddled with creationist notions, and will severely hinder, rather than improve, science teaching.