"In 1729, French scientist Jean-Jacques d'Ortous de Mairan conducted the first experiment designed to distinguish an endogenous clock from responses to daily st

"In 1729, French scientist Jean-Jacques d'Ortous de Mairan conducted the first experiment designed to distinguish an endogenous clock from responses to daily stimuli. He noted that 24-hour patterns in the movement of the leaves of the plant Mimosa pudica persisted even when the plants were kept in constant darkness." https://en.wikipedia.org/wiki/Circadian_rhythm#History https://en.wikipedia.org/wiki/Circadian_rhythm#History second paragraph