<P> The evolution of the peppered moth is an evolutionary instance of directional colour change in the moth population as a consequence of air pollution during the Industrial Revolution . The frequency of dark - coloured moths increased at that time, an example of industrial melanism . Later, when pollution was reduced, the light - coloured form again predominated . Industrial melanism in the peppered moth was an early test of Charles Darwin's natural selection in action, and remains as a classic example in the teaching of evolution . Sewall Wright described it as "the clearest case in which a conspicuous evolutionary process has actually been observed ." </P> <P> The dark - coloured or melanic form of the peppered moth (var . carbonaria) was not known before 1811 . After field collection in 1848 from Manchester, an industrial city in England, the frequency of the variety was found to have increased drastically . By the end of the 19th century it almost completely outnumbered the original light - coloured type (var . typica), with a record of 98% in 1895 . The evolutionary importance of the moth was only speculated upon during Darwin's lifetime . It was 14 years after Darwin's death, in 1896, that J.W. Tutt presented it as a case of natural selection . Due to this, the idea widely spread, and more people believed in Darwin's theory . </P>

What caused natural selection among the peppered moths of manchester england