Kettlewell's experiment

Kettlewell's experiment was a biological experiment in the mid-1950s to study the evolutionary mechanism of industrial melanism in the peppered moth (Biston betularia). It was executed by Bernard Kettlewell, who was working as research fellow in the Department of Zoology, University of Oxford. His aim was to investigate the scientific reason for the appearance of dark-coloured moth since Industrial Revolution in England in the 19th century. He conducted his first experiment in 1953 in the polluted woodland of Birmingham, and his second experiment in 1955 in Birmingham as well as in the clean woods of Dorset.

The experiment found that birds selectively prey on peppered moths depending on their body colour in relation to their environmental background. Thus, the evolution of a dark-coloured body provided a survival advantage in a polluted locality. The study concluded that "industrial melanism in moths is the most striking evolutionary phenomenon ever actually witnessed in any organism, animal or plant." It is now regarded as the classic demonstration of Charles Darwin's natural selection in action and one of the most beautiful experiments in evolutionary biology.

The Industrial Revolution in Great Britain caused extensive pollution, and industrial cities such as Manchester and Birmingham were covered with black soot. R.S. Edleston was the first to identify the unusual black peppered moth in 1848 in Manchester. By the end of the century, it was recorded that the black moth, the carbonaria type, outnumbered (90% in some regions) the natural white ones, named typica. There were conflicting ideas as to the biological basis of this so-called industrial melanism. Humidity, environment, heredity, disease, temperature and protection (such as camouflage) were the factors put forward. J. W. Tutt was the first to come up with natural selection as an explanation, and stated in 1894 that the phenomenon was due to selective predation by birds. With the rise of evolutionary statistics, the theoretical background was set. For example, J.B.S. Haldane estimated in 1924 the rate of evolution by natural selection in the peppered moth in his first series of A Mathematical Theory of Natural and Artificial Selection. He estimated that for the peppered moth having reproductive cycle in a year, it would take 48 generations to produce the dominant (melanic or black) forms, and the melanic population could dominate the entire moth population after 13 generations. He concluded that "the only probable explanation is the not very intense degree of natural selection". University of Oxford zoologist E. B. Ford supported the bird-predation hypothesis. To experimentally investigate the issue he recruited Bernard Kettlewell in 1952 under a grant from Nuffield Foundation.

...
Wikipedia