The differing frequencies of the different color varieties of peppered
moths can better be explained by the direct effects of mutagenic
pollutants, since the usual explanation of differential bird predation
lacks support.
The explanation of differential bird predation affecting frequencies of
color varieties does not lack support. On the contrary, support for
the basic story is overwhelming (Grant 1999; Majerus 1999). Wells and
others simply ignore the bulk of the research and pick out the few
dissenters and the disagreements about minor details.
An explanation in terms of the direct effect of pollutants fails.
The early experiments (by Helsop Harrison) that claimed to show such
an effect lacked appropriate controls, could not be replicated, and
reported mutagenesis levels that were more than enough to induce
complete sterility (Majerus 1999).
