André Klarsfeld

Biological Clocks Publication date : October 1, 2009

What do the following have in common: jet lag following a transatlantic flight, difficulties falling asleep on Sunday night after sleeping-in for two consecutive mornings, and health problems linked to night-time work or to daylight saving time? The answer is the biological clocks that govern our life rhythms, although we are unaware of them most of the time.

Biological clocks are an essential aspect of the living world — and not just of the animal world since plants and even microbes possess them. They allow every living organism, even if it appears to be at rest or sleeping soundly, to store energy resources for its active phases, whether diurnal or nocturnal. But biological clocks have other basic, and sometimes more unexpected, functions: initiating the mating season, guiding birds and butterflies in their seasonal migrations, and directing bees in their nectar-gathering activities. As early as 1729, biologists had the first inklings of the temporal orchestration of all life forms. Yet the existence of “biological clocks” was not accepted until the mid-twentieth century. Since then, biologists have been trying to understand how living beings measure time, internally, with such great precision, how they “set” their internal clocks to solar time, and how they produce the physiological cycles that give the day its rhythm.

The result of a long process, the understanding of biological clocks has had a major impact on our knowledge and treatment of numerous pathologies.

This book shows how, from insects and migratory birds to human beings, time regulates the behaviour of all life forms.

For André Klarsfeld, “the daily rhythms are not just the consequence of the earth's rotation; biological evolution has succeeded, by producing actual living clocks, to do what for a long time seemed to depend solely on a divine prerogative: inscribing regularity in the Universe.” Thanks to an uncommon talent for scientific popularisation, this is the immanent order that he enables the reader to discover.

André Klarsfeld is a research fellow at the Alfred Fessard Institute of Neurobiology of the Centre National de la Recherche Scientifique (CNRS). He is the co-author (with Frédéric Revah) of Biologie de la mort.