Five Figures in the History of Chronobiology
The individuals who influenced chronobiology hail from different disciplines, and made contributions over hundreds of years. Here we will look at just a few of the biologists who helped shape the field:
~ Colin Pittendrigh and Jürgen Ashoff, often considered founders of chronobiology
~ Seymour Benzer, who discovered an important mutation in fruit flies
~ Jean-Jacques de Marain, the first person to identify a circadian rhythm
~ Joseph Takahashi, who conducted key genetic studies
Colin Pittendrigh (1918-1996) developed the idea that the internal clock is independent of the behaviors it controls. This insight enabled investigators to study the circadian clock across species, from fruit flies to rats.
Pittendrigh also argued that circadian rhythms were basically internally driven (vs dependent on the environmental), and carried out series of experiments to demonstrate this point.
Jürgen Ashoff (1913-1998) focused on entrainment in birds and mammals–the idea that circadian rhythms were generally synchronized to the solar cycle of day and night. He was especially interested in the problems that occurred when Zeitgebers (cues that can help maintain circadian rhythms, such as bright light) disrupted natural patterns of rest and activity.
Seymour Benzer (1921-2007), and his student, Ron Konopka, used forward genetics to study circadian rhythms in fruit flies. Forward genetics entails identifying the genes responsible for a given physical or behavioral trait by generating random mutations in the flies, and then observing the results. Benzer and Konopka identified a single gene on the X chromosome (the period, or per gene) that was responsible for circadian rhythms.
Jean-Jacques de Marain
Jean-Jacques de Marain (1678-1771), a geophysicist and astronomer, as well as a biologist, inspired the science of circadian rhythms with his observations of Mimosa pudica in 1729. (See History of Mystery.) However, he was not entirely convinced that he was witnessing circadian rhythms in the heliotrope plant; perhaps, he thought, the daily movements of the plant were due to magnetic fields, or temperature changes. It is also possible that the idea that a plant might have an internal clock, and perhaps even a soul, unnerved him. In any event, since he was busy with his work as an astronomer, he did not have the time to follow up.
A colleague wrote up de Marain’s observations under his friend’s name, and published them in the Proceedings of the Royal Academy of Paris. This inspired a bouquet of botanist to see whether they could find an alternative explanation to the idea of an endogenous circadian clock, ending with Augustus Pyramus de Candolle in the nineteenth century. De Candolle controlled for light, temperature, and humidity in his experiments before concluding that circadian rhythms really existed in plants.
Joseph Takahashi pursued several lines of research on circadian rhythms. One of them involved looking at the effects of mutant clock genes on the behavior of mice. He showed that mice with an abnormal clock genes had strange sleeping patterns: they napped off and on, rather than getting a solid block of sleep during the day as mice typically do. More importantly, Takahashi showed that the abnormal clock genes seemed to disrupt other mouse behavior, such as eating, learning, and addiction.
Other Leading Researchers
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Elizabeth Saenger, PhD