Rhythms of Life: The Biological Clocks that Control the Daily Lives of Every Living Thing [Paperback]

What do the disasters of the _Titanic_, the _Exxon Valdez_, Chernobyl, Three Mile Island, and the Union Carbide plant explosion in Bhopal all have in common? They involved human error, and they all happened when the humans ought, by biological fiat, to have been sleeping. We are ruled by our clocks now, but even in the unnatural world we have made for ourselves, we cannot get away from the natural clocks that our cells expect us to follow. Like almost all living things in the planet, from plants to bacteria to birds, we have "a biological clock that was first set ticking more than three billion years ago." In _Rhythms of Life: The Biological Clocks that Control the Daily Lives of Every Living Thing_ (Yale University Press), Russell G. Foster, a professor of molecular neuroscience, and Leon Kreitzman, a writer and broadcaster, have examined the investigations of a relatively new science, chronobiology, to show just how much sway natural time has over us and other organisms. It isn't just a tale of sleepy people in control making bad judgments, although cognition and prudence do have their daily cycles. We tend to have babies (natural birthing) in the early mornings, and heart attacks in the later morning, and lovemaking around 10 p.m. Physical coordination, liver metabolism, body temperature, heart rate, kidney function, and much more all are paying attention to the biological clock, and when we jump time zones or do shift work, we do so at our peril.

Many of these cycles are specifically examined here, along with the historical hunt for the biological roots of the rhythmicity. A couple of the chapters dealing with the dance of molecules will be daunting for those uninitiated into the basics of cellular biology, but they do well to show the intricacies of the molecular mechanisms and the depth of work that has been done in this field. There are not just daily rhythms, but annual ones. Migratory birds the whole world over know when to start their travels north or south; they do so not by counting the days or paying attention to when the weather changes, but by regulation from the annual changes of lengths of day and night. Plants cannot migrate, but they are regulated by day length, too; wheat flowers, for instance, when the days get long enough, and barley does so when the days start to shorten. The almost universal attention that species pay to daily or annual changes indicates that success comes from being able to predict when winter, or summer, or nightfall, or other events, are coming, and from timing leaf drop, coitus, or swimming upstream to meet the optimum times and conditions. Evolution has selected the species that are best able to predict the future.

In the famous experiments where humans lived in caves or other light-deprived environments, with no capacity to tell time, they eventually locked into their own cycles of a little more than 24 hours. Like most creatures, we have an internal daily rhythm which is not exact, but only approximate; the day night cycle (or for us, such cues as an alarm clock) "entrain" the internal cycle and keep it synchronous with the rest of the creatures on Earth. There are mutant rats and flies who have cycles that are too long or too short, and researchers have productively transplanted brain parts to find out where the actual clocks are. Chronobiologists (a term that even some chronobiologists think of as pompous) are not just doing ivory tower investigations. There are many practical implications of this sort of work. Breast cancers, for example, have an annual pattern of increased and decreased growths, and so searching for the cancer would be more productive at certain times of the year. Chemotherapy for cancers involves poisoning the cancer cells with drugs that are also poisons for regular cells, but cancer cells, with their out-of-control growth, lose their rhythm of growth and division that normal cells retain. Thus it is possible that administering anti-cancer drugs at the time of day when they will interfere the least with the normal cells could reduce the worrisome side effects of the drugs. Asthma is most prevalent at night; medicine for it would be best taken in higher doses at nighttime, rather than every eight hours. The timing of doses in some cases may be as important as what the doses contain. The authors have given a detailed but readable introduction into a new science that will have increasing importance for human health as more is learned.

For the first few million years of life, time was measured by sunrise and sunset. Now we have switched to clocks. But the biological clocks that are within all of us don't know how to read clocks. Breakfast, lunch and dinner occur at standard times. Tooth pain is lowest after lunch; proof reading and sprint swimming are best performed in the evening; labour pains more often begin at night and most natural births occur in the early hours; sudden cardiac death is more likely in the morning (from Chapter 1).

The study of biological clocks has gone on for a long time, but as a science is a fairly recent development. Research in just the last few years has dramatically altered the way scientists view them. This book is a snapshot of the way the science appears right now. The pair who wrote the book are a leading researcher in the field and a professional science writer. This is a good combination that gives good enjoyable writing combined with accurate reporting.

This book about biological clocks can be read on two levels. Much of it is a popular account of time and its physiological effects; it is informative and entertaining for non-scientist readers, and easily intelligible, at least until it enters into technical details. It contains much interesting information about circadian and other rhythms, and their effects in different organisms, starting from the evidence gathered to prove that internal clocks really exist. We can learn, for example, that camels can stand far greater variations than humans in their body temperature, which may rise as high as 41 degrees Celsius (106 degrees Fahrenheit) in the afternoon or as low as 34 degrees (93 Fahrenheit) during the night, and that this is an adaptation to prevent dehydration. Dictyostelium discoideum, however, which has surely taught us more than camels have about biological rhythms, is not mentioned. In the context of temporal effects in human medicine we learn that the use of chemotherapy to treat cancer can vary widely in effectiveness according to the time of day at which the treatment is administered, one of numerous examples where the moment of treatment is important. The book concludes with some practical advice on the use of melatonin to combat jet-lag.

Biochemists, however, are also interested in reading about the mechanisms that underlie circadian rhythms: if there is an internal clock, its time-keeping capability must be derived from the kinetic properties of its components. The study of these, as revealed by the pioneering work of Britton Chance and Benno Hess from the 1960s onwards, and more recently that of Albert Goldbeter and others, is surely fundamental to any analysis of physiological time-keeping. Astonishingly, however, the book mentions none of this, and barely recognizes that it is dealing with a kinetic problem at all. Authors who can find room for references to St Augustine, Homer and the New York Times could surely have managed to mention the fundamental biochemical investigations of its subject matter. The book contains quite a lot of analytical-laboratory biochemistry, measurements of levels of different biochemical components -- though not, remarkably, cyclic AMP -- at different times of the day. It also presents some of the molecular biology of the components a clock might have, but the analysis of how a functioning clock might result from putting these together is too superficial to be satisfying, especially as it is entirely qualitative.

All this would be like a book about mechanical clocks that entertained its readers with anecdotes about Galileo, and described clocks in some detail, observing, for example, that every clock contains a pendulum or something similar, but did not mention the physical properties of the pendulum responsible for the time-keeping. Of course, the authors may have just taken too much to heart Stephen Hawking's comment that each equation in a book decreases its sales by half, as they have arrived at a book without a single equation. But a discussion of time-keeping without kinetics is bound to be as superficial as a course on metabolism without chemistry.

In one remarkable sentence, the authors tell us that "Erwin Schrödinger is best known for his metaphorical cat," but Schrödinger's claims to greatness go beyond that! This is trivial in itself, of course, but it is symptomatic of a more alarming characteristic of modern scientific writing, in which flippancy is valued more highly than accuracy.

In summary, if you want a gentle and often entertaining account of biological clocks, then this book can be thoroughly recommended, but if you are looking for some serious biochemistry you will need to look elsewhere.

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