Origins: A Brief Account of the Ancestry of Circadian Biology

Who were the investigators and what was the path that enabled the launch of modern mechanistic research on circadian biology in the 1970s? Here we trace the origins of ideas from antiquity to the experimental study of the daily movements of leaves; on to the twentieth-century realization that circadian rhythms are widespread, endogenous, and innate; and finally to the appreciation that such rhythms could be utilized by organisms for the measurement of time. The conceptualization of the internal “clock” metaphor was key to the wave of mathematical, neurobiological, and molecular genetic advances that has transformed the field over the last 50 years.