What do secondary school boys understand about evolution and heredity before they are taught the topics?

Results are reported of an investigation into what schoolboys understand about evolution and heredity before they are taught these topics. This was explored by means of open-ended interviews. It was found that the boys' understanding had seven foci: evolution as a phenomenon, why evolution occurred, the process of change, adaptation, selection, chance, and inheritance. The concept of adaptation was found to be particularly well established, that of chance least so. Naturalistic and Lamarckian interpretations of evolution were predominant. Key concepts in the boys' existing knowledge were identified and incorporated into outline teaching schemes.