The idea that a particular physical feature, either normal or abnormal, is hereditary is probably as old as our species itself. However, as has been noted by many other writers, tracing the origins of an idea is a formidable, if not impossible, task. Clearly, the concept of “like begets like” found a practical expression in the early domestication of animals; breeding stock was chosen on the basis of favorable traits. The first tangible evidence that human beings had at least a glimmer of the notion of heredity can be found in the domestication of the dog some 10,000 years ago. Yet it is only in the past 100 years that we have begun to understand the workings of heredity.

This essay traces the development of the concept of heredity and, in particular, shows how that development has shed light on the host of hereditary and genetic diseases we have come to recognize in humans. It begins with a brief discussion of some basic concepts and terms, which is followed by an outline of the heuristic model of genetic transmission that has come to be the standard of modern medical genetics. Once this groundwork is in place, the history of the study of human genetic disease is developed from the earliest records, through the birth of medical genetics, to the molecular era. Naturally, a detailed narrative of this history would require several volumes. Therefore, some events and ideas have been omitted or treated only cursorily.