March 2003
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Reviewed by Lynne Lamberg |
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Returning to the University of Massachusetts from a Florida field trip, biologist John Palmer tucked a giant land crab in a plastic bag into his attaché case, and carried a box containing another 150 crabs aboard the plane. When people seated near him asked what was making the scratching noises they heard, Palmer told them he studied biological clocks in crabs and other aquatic life forms. The crab in his bag spent the day nearly motionless, he said. Its activity cycle started at 6 p.m. When the plane landed at 7 p.m., Palmer opened his case to replace some papers. The forgotten crab burst out, its huge claws open, briefly terrorizing Palmer's fellow passengers. That misadventure sparked this book, an entertaining exploration of internal time-keeping for the general public. A biological rhythms researcher for the past 40 years, Palmer studied a one-celled organism, Euglena, early in his career. This creature surfaces from the River Avon in southern England as the tide recedes, making the river's mud look green. As the tide returns, Euglena burrows down, and the mud blackens. Patrons of a pub overlooking the river found it entertaining to see a Yank traipse through the malodorous muck, Palmer relates. He parlayed his knowledge into winning bar bets with them. Collecting mud from sites successively further down the river in Petri dishes, he wagered a pint of bitter over his ability to predict when his mud samples would change color. Thanks to Euglena's clock-work regularity, Palmer claims he essentially drank free the entire year he spent on this project. In his book, Palmer reports findings from dozens of studies on biological clocks in plants, animals, and humans. In their first week of life, human babies predictably sleep longer at night than in the day, 8.5 hours between 8 p.m. and 8 a.m., but only 6.5 hours between 8 a.m. and 8 p.m. When 10 weeks old, they log 10 hours at night, and 3.5 hours in the daytime. When confined to windowless apartments with no time cues, adults live on internal days slightly longer than 24 hours, going to sleep and arising a bit later each day. In these time isolation studies, people typically lose track of time, for they can't tell whether an episode of sleep represents a brief nap or slumber lasting several hours. When camping in far northern latitudes in the summer when the sun never sets, people given sham watches that shrink or expand the day unknowingly adapt their sleep-wake cycles to those dictated by the clock. Yet some of their inner rhythms, including those of chemicals excreted in urine, still follow normal 24-hour schedules. Sexual rhythms in many species correspond to specific phases of the moon. Although poetry and song imbues the moon with magic for human romance, the truth—at least in married couples—proves more prosaic. Palmer and his colleagues asked 78 husbands and wives to send separate postcards noting each time and date the couple had intercourse. The researchers' analysis of more than 5,500 couple days of data found 11 p.m. to 1 a.m. the peak hours for intercourse. Sexual activity showed no relationship to lunar cycles. Sexual habits in humans thus appear to follow a social rhythm, not a biological one. With the breadth and confidence of a master teacher, Palmer retains the enthusiasm and curiosity of a neophyte. He shares that joi de vivre with his readers, making learning not only easy but fun. He cites Dracula's dilemma—the need for the Count to know it is dark before he lifts the lid of his coffin—to show how internal clocks prepare us for periodic changes in our environment. Moving from Dracula to bats, Palmer segues easily to an explication of jet lag. Should you ever find yourself sitting next to Palmer on a plane or at a dinner party, this graceful book suggests he'll be an amiable and droll companion. But keep an eye on his attaché case. |
© 2003
WebSciences and Lynne Lamberg |
THE
LIVING CLOCK: