The Timing of Biological Clocks

Scientific American Library Series #19

by Arthur T. Winfree

Examines circadian rhythms, tells how biological clocks are reset, and discusses time zones, consciousness, and clocks

199 pages, Hardcover

First published November 15, 1986

Reviews

[Mengsen Zhang · Rating 5 out of 5]

Winfree is a genius. That's it. I consider him one of the godfathers of biological rhythmicity. This book gives a very clear mental image and physical images (real data visualization as well as computer graphics) of the mathematics/geometry/topology of the phase response of nonlinear oscillators in individuals and coordinated collectives-- essential learning material for beginners in the field of study. He demonstrated precisely and poetically the conversation between experiments and mathematics. Such a wonderful mind.

[Keenan · Rating 2 out of 5]

Circadian (circa, "about" + dia, "day") refers not to cycles which follow the day, but rather the curious feature of living things, from slime molds to humans, to have internal clocks that are "about" 24 hours that regulate when we're tired, when we feel pain most acutely, and even when it's best to take certain medication. Throw a person in a room without clocks or sunlight and their rhythms will naturally follow these internal mechanisms (often tuned to 25 or 26 hour cycles instead), and its the role of stimuli like the day and night cycle to bring us back in check with the Earth's rotation.

One curious feature of biological clocks is that a large enough stimulus initiates the resetting mechanism, e.g. a strong burst of sunshine will remind a flower it's time to open up. If the simulus is too weak, however, it will just stay on with its old phase. Naturally then, there must be a phase singularity, some crossover point between too weak and too strong a signal, similar to how all time zones converge at the poles or how there are points in the oceans where the tide is constant. Playing around with these kinds of stimuli can force biological systems into equilibria that wouldn't be seen in nature, for example by mixing glowing plankton from different time zones together and seeing whether their cycles reach a compromise phase.

A very large portion of the book is dedicated to experiments that explore the aforementioned phase singularity in flies, mosquitoes, flowers, bioluminsecent plankton, and yeast cells, along with far too many proofs (even some with torii) for why the singularity must exist. The bevy of new charts and tools used to convey the data seemed overly complex and antiquated (the book was published in 1987 mind you), with color phase diagrams and time crystals littered throughout. Perhaps the interesting content in this book would be best served by a modern revamp of all the diagrams and pictures, but maths readers 33 years later just have too many other ways to visualize these concepts.