Industrial melanism is a term used to describe the evolutionary process in which darker individuals came to predominate over lighter individuals because of the Industrial Revolution. This occurred as a result of natural selection in which a black 'melanic' form arose by a recurring random mutation, but its phenotypic appearance had a strong selective advantage in industrial areas.
Related Theory
During the period when the number of coal burning factories in England was increasing (during the so-called Industrial Revolution) it was noticed that the number of melanic individuals of the species of Peppered Moth (Biston betularia) was becoming more common. Originally rare in the population of normally light-coloured moths, the frequency of the melanic form increased in polluted areas until it was over $90 \%$. This change in colour has come to be known as "industrial melanism."