Biological clocks are an integral part of life on Earth, from the simplest one-celled organisms all the way to human beings. The clock never seems to stop. Every day, it seems, we’re
and exciting ways. And almost without even trying to, the Unifighting it: rushing to get to work, getting versity of Pennsylvania has beerrands done, catching whatever sleep come one of the world’s leading we can. There’s never enough time to do centers of chronobiology, with cutwhat we need or want to do, and just ting-edge research that involves when we almost seem to get caught up almost every one of Penn Medion the weekends or our days off, the clock cine’s science departments and sevkeeps going and the merry-go-round starts eral departments of its hospitals. all over again. “Chronobiology is biological Amita Sehgal, shown here with Christine Dubowy, a graduate That’s life for most people in our hectic timing,” says Amita Sehgal, Ph.D., student, has found genes that regulate the 24-hour cycle of rest and activity. 21st-century society. Undoubtedly, most the John Herr Musser Professor of of us have occasionally cursed creators of Neuroscience and a Howard Hughes tronomer Jean-Jacques d’Ortous de Mairan the merciless work schedules, keepers of Medical Institute Investigator. “It basically noted how certain plants responded to the deadlines, masters of the timebound refers to the process by which organisms different times of day or observed how obligations by which our economy and time physiology and behavior, so that the behavior of animals varied with light society continuously operate. But as arbieverything takes place in a rhythmic fashand dark. But no one entertained the idea of an actual biological clock within Chronobiology, says Amita Sehgal, “basically refers to the the body. Perhaps it was because natural process by which organisms time physiology and behavior, rhythms are so all-pervasive and, well, so that everything takes place in a rhythmic fashion.” natural, they were simply taken for granted – or it may be that even as Enlightenment science seemed to increasingly trary as they may sometimes seem, clocks, ion.” The persistent rhythms of life, the reveal the workings of a mechanistic, clockcalendars, and schedules aren’t an invenbody clocks that control when you wake, work universe guided by Newtonian tion of humans. Clocks – mechanisms to sleep, eat, digest food, and perform nearly physics, the notion of people under the track and mark the passage of time – are every other function of a living organism, control of a clock seemed unnatural, an integral and indispensable part of life are all the province of chronobiology. even somehow blasphemous. on Earth, from the simplest and most Although humans have always been at By the 20th century, however, it had primitive one-celled organisms all the least subliminally aware of how their own become clear that there were important way to human beings. bodies and other life forms are affected connections between the ticking of the The study of how biological clocks by natural rhythms such as the day-night clock and the workings of life, even within work to control and regulate almost evcycle, the seasons, and the tides, science our own bodies. Scientists discovered that ery function of life is called chronobiolpaid little attention to such phenomena blood pressure varies naturally by time of ogy. It’s a rich discipline encompassing a for most of human history. In the 18th day and began to think about issues such broad range of sciences, synthesizing century, curious types such as Swedish as sleep, hormonal cycles, and work their techniques and viewpoints in new naturalist Carl Linnaeus and French as-
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