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Artificial Life

Winter 2012, Vol. 18, No. 1, Pages 123-123
(doi: 10.1162/artl_r_00052)
© 2011 Massachusetts Institute of Technology
Wetware: A Computer in Every Living Cell. Dennis Bray. (2009, New Haven, London: Yale University Press.) $28 (hardback), 267 pages.
Article PDF (36.73 KB)
Abstract

Make no mistake, this book falls into the popular science category: It is accessible to the general reader without a scientific background, but it also makes a scientifically interesting argument. At one level, Wetware by Dennis Bray is an easy introduction to systems biology—the relatively new science born from the union of molecular biology with information science. At another, it proposes a model of the cell as a computer, not of the von Neumann kind, but a rather elaborate neural network type of computation system. This idea is expanded to include a few aspects of multicellular information processing, especially with living neurons, but perhaps these are just to support the main argument, as they receive scant attention. The main focus for Bray is the molecular signaling network, especially illustrated by the generation and control of directed movement in bacterial cells.

Using no more than first-year university-level science, we are introduced to molecular sensors, messengers, switches, transistors, amplifiers, logic gates, and transducers: a full toolbox of biochemical information-processing components. These labels are just analogies, of course, but identifying functional equivalents to computer hardware components provides a model of molecular networks as “wired-up” wetware. It is the constant adjustment of concentration and state of thousands of computationally functional proteins in the cell that amounts to its living. In the sense that this chemistry of life is information processing, we could conclude that living is computing, though Bray leaves that to the reader to conclude.

Those unfamiliar with cellular biochemistry will no doubt be fascinated to learn how proteins can change shape and therefore subtly alter their chemical behavior in response to specific signals, enabling semantic communications between molecules as the state of one influences that of others in turn. Vast and bewilderingly complex networks of molecular interactions operate and control the inner workings and the behavior of the cell, appearing to give it a life of its own. If you ever ponder on the deep meaning of life, it could be that this will give a significant mechanistic insight. The probabilistic nature of chemical interactions, molecule by molecule, scales up to give even bacteria individual identities, as network connections subtly and randomly differ from one cell to another. This is a recurring theme and one obviously close to Bray's heart: Real biology is considerably (almost unimaginably) more complicated than any model that could be useful. Indeed he gets close to accusing some modelers of self-deception (he calls it “reality distortion”), singling Stephen Wolfram out for near-derision; he is far kinder to Stuart Kauffman.

Bray is a hugely respected molecular biologist, so what he says about molecular mechanisms is solid and well written, and he seems to judge the tradeoff between technical detail and engagement well. This is good news for the information scientist with little background in biology, because this book really does open the mind to the amazing idea that living is computing. On the other hand, Bray's handling of information science seemed more clumsy; for example, the explanation of artificial neural networks was all too familiar, and the description of mechanical tortoises was quaint and amusing, rather than illuminating. Biologists may find some of the explanations in their own field similarly plodding, but plausibly marvel at the tortoises—to be fair, this is the unavoidable problem of multidisciplinary approaches.

Wetware introduces the reader to genetic, biochemical, and neural networks in real living organisms, explaining the foundations of their inner workings. It is certainly not a textbook, not just because of the frequent expressions of the author's personal opinions, but more because he is so selective in subject material. Bray uses the book to express a big idea—that of living as computing—so it is more a well-illustrated argument than a tour of cellular biochemistry or systems biology. I think it is all the better for that.