The Nature Institute

The Nature Institute 
20 May Hill Road, Ghent, New York 12075  Tel: (518) 672 0116

Home | Our Education Programs | Our Publications | Content Areas | Writings Ordered by Author | Resources and Links | Contact Us | Search

In Context #8 (Fall, 2002, pp. 8-10); copyright 2002 by The Nature Institute

The Tyranny of a Concept:
The Case of the Peppered Moth

Craig Holdrege

The peppered moth is one of the most celebrated textbook examples showing natural selection in action. A dark variety of the otherwise light-colored peppered moth appeared in England in the mid-nineteenth century and its numbers continued to grow in the industrial areas of England. In the 1950s Bernard Kettlewell set out to show experimentally that the dark variety of moth prospered because it was better camouflaged against the soot-darkened, lichen-free tree trunks in industrial areas. He released light and dark peppered moths onto tree trunks in the polluted forests. He not only recaptured (via lamps at night) proportionately more dark moths than light moths, but also observed birds feeding predominantly on the light moths. He obtained exactly the opposite results in an unpolluted forest with much lighter tree trunks. He concluded that natural selection via bird predation in polluted forests was causing peppered moth populations to evolve from the light to the dark variety.

This story quickl