Majerus's experiment

 

Majerus's experiment

From 2001 to 2007, Majerus carried out experiments in Cambridge to resolve the various important criticisms of Kettlewell's experiment. During his experiment, he noted the natural resting positions of peppered moths. Out of the 135 moths examined over half of them were on tree branches, mostly on the lower half of the branch, 37% were on tree trunks, mostly on the north side, and only 12.6% were resting on or under twigs. He then added an experiment to find if bats, not birds, could be the main predators. He looked at a number of species of bird actually preying on the moths, and that differential bird predation was a major factor responsible for the decline in carbonaria frequency compared to typica. He described his results as a complete vindication of the natural selection theory of peppered moth evolution, and 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."

Majerus died before he could complete the writing up of his experiments, so the work was carried on by Cook, Grant, Saccheri and Mallet, and it was published on the 8th February 2012 as "Selective bird predation on the peppered moth: the last experiment of Michael Majerus". The experiment became the largest study of industrial melanism ever, involving 4,864 individuals in a six-year investigation, and it confirmed that melanism in moths is a genuine example of natural selection involving camouflage and predation. This is what they had to say: "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".