Background – The story concerning England’s Pepper Moths (Biston betularia) originally seemed very straightforward. The research is attributed to one H.B. Kettlewell, who is reported to have said that Darwin would be overjoyed to see the vindication of his theory. The insects used to be mostly of a light form, with occasional darker (melanic) forms. Light-coloured lichen growing on tree trunks meant that the light forms were very well camouflaged, while the dark ones would ‘stand out’ to the eyes of hungry birds. Pollution from the industrial revolution is said to have killed off much of the pale lichen covering the tree trunks, thus darkening them, so that now the dark forms were better camouflaged. Therefore, it made sense that hungry birds would eat more of the lighter ones, so the dark ones would become the dominant form. Kettlewell’s experimental observations were supposed to have shown that this is indeed what happened. Then, as pollution began to be cleaned up, the tree trunks became lighter again, so light moths resting on the tree trunks would now be less easily seen, thus the ratio shifted the other way.
Photographs were taken of dark and light forms resting on the tree trunks, showing how obvious the camouflage differences were. To further ‘clinch’ the case, birds were filmed preferentially ‘picking off’ the less camouflaged forms.
Exposed - The bubble started to burst as people finally faced the awkward fact that Pepper Moths do not rest on tree trunks in the daytime. Instead, they hide under leaves in treetops.
As the story unravelled it turned out that:
The famous photos of light and dark moths resting on a lichen-covered tree trunk were faked by pinning and/or gluing dead moths onto logs or trunks.
The filmed ‘experiments’ involved either dead moths, or laboratory moths (so stuporous they had to be warmed up first), placed on tree trunks in the daytime.
– Carl Wieland, M.B., B.S. Creation 25(1) 15, 2003
The bottom line is that even if these experiments were genuine, the results would be far from proof of evolution in action, but merely showing that before and after the industrial revolution there was already genetic information present for dark and light moths.