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Horizon Discovery

Peppered Moths Re-examined

The textbook example of Darwinian evolution is tested and confirmed.

By | February 9, 2012

image: Peppered Moths Re-examined The melanic carbonaria peppered moth (left) and the more common light-colored typica (right).Wikipedia, ??????? ???????

The melanic carbonaria peppered moth (left) and the more common light-colored typica (right).WIKIPEDIA

Although the peppered moth has been the poster child of Darwinian evolution since the late 19th century, over the past decade there’s been a public debate questioning the validity of this textbook example. In particular, scientist questioned whether birds were really the agents selecting between the light– and dark-colored moths, which rest on light or soot-covered trees, among other things.

To lay the matter to rest, a late evolutionary biologist from the University of Cambridge, Michael Majerus, carried out a 7-year study in a hamlet close to his home in Cambridge, England, the results of which were published yesterday (February 8) in Biology Letters.

“These data provide the most direct evidence yet to implicate camouflage and bird predation as the overriding explanation for the rise and fall of melanism in moths,” the authors wrote in the abstract.

According to Majerus, the controversy started back in the late 1990s, when Nature ran a review of his book Melanism: Evolution in Action suggesting that “the peppered moth case is fatally flawed as an example of Darwinian evolution,” he explained in a talk back in 2004. Newspapers and other media outlets picked up the review and further discredited the peppered moth story, providing fodder for evolution skeptics.

As a result, Majerus decided to embark on a long-term project, releasing and tracking the fates of 4,864 moths. He found that dark moths had indeed a lower survival than light-colored moths in the relatively unpolluted Cambridge forests.

Majerus died in 2009 from an aggressive case of mesothelioma. Four of his colleagues then proceeded to analyze and publish his results.

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Comments

Avatar of: Daniel Dvorkin

Daniel Dvorkin

Posts: 20

February 9, 2012

Why the use of the weasel phrase "evolution skeptic?"  We all know who the people are who gleefully point out any flaw (real or imagined) in the peppered moth story, and they're not people to whom the word "skeptic" can meaningfully be applied.

Avatar of:

Posts: 0

February 9, 2012

Why the use of the weasel phrase "evolution skeptic?"  We all know who the people are who gleefully point out any flaw (real or imagined) in the peppered moth story, and they're not people to whom the word "skeptic" can meaningfully be applied.

Avatar of:

Posts: 0

February 9, 2012

Why the use of the weasel phrase "evolution skeptic?"  We all know who the people are who gleefully point out any flaw (real or imagined) in the peppered moth story, and they're not people to whom the word "skeptic" can meaningfully be applied.

Avatar of:

Posts: 0

February 13, 2012

I see kind reproducing it's own kind.

Avatar of:

Posts: 0

February 13, 2012

Define kind.  Is it moth kind?  In which case, you are correct, but that's not what the study is about. Is it peppered moth kind?  The same.

However, if it is melanistic vs. non-melanistic moths, then you are wrong.  The actual genetics of the melanin production aren't know, but what are you willing to bet that it is a single gene with a simple dominant allele and a simple recessive allele?  In that case, the study shows exactly what it claims to show...

that is bird predation significantly affects the population of each color morph.  This is a fairly simple concept called natural selection.  The % of dark and light moths in a population is determined by the environment (including the predators).  That's all this study shows... well that and that claims to the contrary (i.e. peppered moths are not an example of evolution) are false.

You see, evolution is not "one species becoming another species".  Evolution is any change in the allele frequency of a population (which this is a fine example of).  That being said, there is no known reason that even minor changes over many, many years could not produce species that cannot interbreed and might be considered different.  In fact, it can happen in one generation, and does so fairly frequently.

Avatar of:

Posts: 0

February 13, 2012

I see kind reproducing it's own kind.

Avatar of:

Posts: 0

February 13, 2012

Define kind.  Is it moth kind?  In which case, you are correct, but that's not what the study is about. Is it peppered moth kind?  The same.

However, if it is melanistic vs. non-melanistic moths, then you are wrong.  The actual genetics of the melanin production aren't know, but what are you willing to bet that it is a single gene with a simple dominant allele and a simple recessive allele?  In that case, the study shows exactly what it claims to show...

that is bird predation significantly affects the population of each color morph.  This is a fairly simple concept called natural selection.  The % of dark and light moths in a population is determined by the environment (including the predators).  That's all this study shows... well that and that claims to the contrary (i.e. peppered moths are not an example of evolution) are false.

You see, evolution is not "one species becoming another species".  Evolution is any change in the allele frequency of a population (which this is a fine example of).  That being said, there is no known reason that even minor changes over many, many years could not produce species that cannot interbreed and might be considered different.  In fact, it can happen in one generation, and does so fairly frequently.

Avatar of: primativewriter

primativewriter

Posts: 22

February 13, 2012

I see kind reproducing it's own kind.

Avatar of: Kevin McCarthy

Kevin McCarthy

Posts: 1457

February 13, 2012

Define kind.  Is it moth kind?  In which case, you are correct, but that's not what the study is about. Is it peppered moth kind?  The same.

However, if it is melanistic vs. non-melanistic moths, then you are wrong.  The actual genetics of the melanin production aren't know, but what are you willing to bet that it is a single gene with a simple dominant allele and a simple recessive allele?  In that case, the study shows exactly what it claims to show...

that is bird predation significantly affects the population of each color morph.  This is a fairly simple concept called natural selection.  The % of dark and light moths in a population is determined by the environment (including the predators).  That's all this study shows... well that and that claims to the contrary (i.e. peppered moths are not an example of evolution) are false.

You see, evolution is not "one species becoming another species".  Evolution is any change in the allele frequency of a population (which this is a fine example of).  That being said, there is no known reason that even minor changes over many, many years could not produce species that cannot interbreed and might be considered different.  In fact, it can happen in one generation, and does so fairly frequently.

Avatar of: apardo1

apardo1

Posts: 1

February 14, 2012

Two data to contrast with this experiment:
- How many time spent the moth laying his eggs? (It is a nocturnal activity, of course, not interfered by the birds). If it is very few, this differential selection happens after the reproduction is finished, and so, had no effect.
- Why in some areas of the UK the melanic variety is still the predominant, in others nearly disappeared, and in others, finally, live the two varieties together without problems?
It seems that the problem is not still closed.
Sincerely yours,
Antonio Pardo
University of Navarra

Avatar of:

Posts: 0

February 14, 2012

Two data to contrast with this experiment:
- How many time spent the moth laying his eggs? (It is a nocturnal activity, of course, not interfered by the birds). If it is very few, this differential selection happens after the reproduction is finished, and so, had no effect.
- Why in some areas of the UK the melanic variety is still the predominant, in others nearly disappeared, and in others, finally, live the two varieties together without problems?
It seems that the problem is not still closed.
Sincerely yours,
Antonio Pardo
University of Navarra

Avatar of:

Posts: 0

February 14, 2012

Two data to contrast with this experiment:
- How many time spent the moth laying his eggs? (It is a nocturnal activity, of course, not interfered by the birds). If it is very few, this differential selection happens after the reproduction is finished, and so, had no effect.
- Why in some areas of the UK the melanic variety is still the predominant, in others nearly disappeared, and in others, finally, live the two varieties together without problems?
It seems that the problem is not still closed.
Sincerely yours,
Antonio Pardo
University of Navarra

Avatar of:

Posts: 0

February 18, 2012

Actually, the melanic form of the peppered moth is now virtually extinct again everywhere in Britain! This is presumably due to the recent selection against the black morph that Majerus identified. The decline followed the almost complete cessation of industrial and domestic coal-burning due to the Clean Air Act. Ilik Saccheri, who is studying the molecular biology of the melanic gene in the peppered moth, is now finding it almost impossible to find wild specimens of the melanic moth.

Avatar of:

Posts: 0

February 18, 2012

Actually, the melanic form of the peppered moth is now virtually extinct again everywhere in Britain! This is presumably due to the recent selection against the black morph that Majerus identified. The decline followed the almost complete cessation of industrial and domestic coal-burning due to the Clean Air Act. Ilik Saccheri, who is studying the molecular biology of the melanic gene in the peppered moth, is now finding it almost impossible to find wild specimens of the melanic moth.

Avatar of: eratosignis

eratosignis

Posts: 1

February 18, 2012

Actually, the melanic form of the peppered moth is now virtually extinct again everywhere in Britain! This is presumably due to the recent selection against the black morph that Majerus identified. The decline followed the almost complete cessation of industrial and domestic coal-burning due to the Clean Air Act. Ilik Saccheri, who is studying the molecular biology of the melanic gene in the peppered moth, is now finding it almost impossible to find wild specimens of the melanic moth.

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