August 24, 2007


Moth study backs classic 'test case' for Darwin's theory (Steve Connor, 25 August 2007, INDEPENDENT)

Now a Cambridge professor has repeated the key predation experiments with the peppered moth, only this time he has taken into account the criticisms and apparent flaws in the original research conducted 50 years ago. Michael Majerus, a professor of genetics at Cambridge University, has spent the past seven years collecting data from a series of experiments he has carried out in his own rambling back garden. It has involved him getting up each day before dawn and then spending several hours looking out of his study window armed with a telescope and notepad.

He wanted a definitive test of the idea that selective predation by birds really was responsible for the differences in the chances of survival among black and peppered varieties of B. betularia. His garden outside Cambridge is in an unpolluted area so in this setting it should be the typical or peppered variety of the moth that has a better chance of survival than that of the black or carbonaria form; it is unlikely to be seen by birds against the mottled background of the lichen-covered trees.

In a seminal description of his results to a scientific conference this week in Sweden, Professor Majerus gave a resounding vote of confidence in the peppered month story. He found unequivocal evidence that birds were indeed responsible for the lower numbers of the black carbonaria forms of the moth. It was a complete vindication of the peppered month story, he told the meeting.

"I conclude that differential bird predation here is a major factor responsible for the decline of carbonaria frequency in Cambridge between 2001 and 2007," Professor Majerus said.

"If the rise and fall of the peppered moth is one of the most visually impacting and easily understood examples of Darwinian evolution in action, it should be taught. It provides after all the proof of evolution," he said.

Criticisms of the 1950s experiments with the peppered month, carried out by the Oxford zoologist Bernard Kettlewell, came to the fore in a 2002 book by the American author Judith Hooper. Hooper's book, Of Moths and Men, suggested that the scientists at the centre of these experiments set out to prove the story irrespective of the evidence.

While the professor has also described drawbacks to Kettlewell's methodology, he was able to address all of these concerns and even tested an idea that Hooper had raised in her book - that it was bats rather than birds responsible for moth predation - a suggestion he dismissed altogether.

Professor Majerus compiled enough visual sightings of birds eating peppered moths in his garden over the seven years to show that the black form was significantly more likely to be eaten than the peppered.

Nothing is more certain in science than that a professor whose sole purpose in life is to derive a certain result will, but Mr. Majerus, unfortunately, never understood that the test case was useless even without the fraud. The persistence of the peppered variety, the ease with which the two varieties breed, and subsequent environmental changes all strike more substantial blows at the utility of Natural Selection than the Creationists have ever landed.

Posted by Orrin Judd at August 24, 2007 8:37 PM

Charlie's, or shall we call him Chas, book was "On the Origin of Species" not "The Recreations of Varieties." Neither the moths nor the finches and their various beaks nor how, if I marry a redhead, I'll have some redheaded children nor how did one breed the first Great Pyrenees from other dogs tells you much about speciation, except by inference.

I wish Ernst Mayer were still alive for comment. Then again, I suppose those who consider this a vindication for Chas are glad he is dead.

Posted by: Ed Bush at August 24, 2007 10:30 PM

Yeah, but the guy's a freakin' genius for figuring out a way to gain fame, fortune and tenure while padding around the house in his slippers with a telescope in his hand.

Posted by: Jorge Curioso at August 24, 2007 11:19 PM