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The Life of the Single Cell

Posted by Josh Rothman  February 28, 2011 11:47 AM

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Every year brings a new discovery about how our worlds and bodies are deeply interlinked - take a look, for instance, at this amazing research, presented at the American Association for the Advancement of Science, about how your social environment affects which of your immune-system related genes are expressed. These kinds of findings testify to the incredible complexity of the body, but also to the dynamism of individual cells. That's the subject of Wetware: A Computer Inside Every Living Cell, a new book by the biologist Dennis Bray, a professor emeritus at the University of Cambridge. Bray's central idea is that much of the behavior we associate with higher organisms can be found in the single-celled world as well.


An amoeba encircles its prey.

Bray's book begins with a detailed tour of the single-celled animal kingdom. Single-celled animals, he points out, are capable of surprisingly complex behavior, quite a lot of it comprehensible even in everyday, human terms. An amoeba, for instance, once it spots prey, will chase after it for as long as fifteen minutes, following it hither and yon over whatever surface forms its world. A small, stationary, single-celled animal called Stentor (for which Bray has an infectious enthusiasm) notices when the water it's living in gets filthy; after trying a number of strategies, more or less like gargling, holding its breath, and so on, it gives up and decamps for another home, swimming around for ten or twenty minutes before settling on a more advantageous spot and setting up shop there. "This entire pattern of actions," Bray writes, "is performed by a fluid-filled sac of membrane less than a millimeter in length!" These animals, which don't have nervous systems, have recognizably animal-like behavior. Systems inside the cell "compute" what ought to be done next.

Bray is careful about his claims: he's not saying that a single-celled animal is consciously aware of the world around it. That doesn't mean, though, that it doesn't behave in an animal-like way. Bray wants to show that "automated" and "animal" can go together when the automation is sufficiently complex and computer-like. His argument is that even single cells "have an intrinsic sensitivity to their environment - a reflexivity, a capacity to detect and record salient features of their surroundings - that is essential for their survival." Bray uses not only biology but also computer science and robotics to explain how this kind of cellular 'self-awareness' works. Ultimately, he argues, the environmentally enmeshed dynamism of single cells "has been amplified and ramified in a thousand different ways":

It is the molecular substrate of our knowledge of the world, including our sense of self - the seed corn of consciousness.

Bray's book is part of a larger trend that's revisiting the distinction between mechanical things and living ones - a computer-science-enabled rethink of a question that's always preoccupied biologists: What is life? Today we know that there is no mystical 'life energy' or élan vital - but a conceptual puzzle remains. On the one hand, a cell is just a lot of biochemistry gathered together in one place; on the other, it's a complex, living thing, with something like needs, wants, and habits. When do we stop seeing an animal as just 'mechanism' and start seeing it as 'alive'? David McFarland's excellent Guilty Robots, Happy Dogs, explores the same territory, but by means of robots rather than cells; Steve Grand's Creation: Life and How to Make It does it using computer programs. Bray's book is another fascinating exploration of the paradoxical border between the automated world and the living one.

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About brainiac Brainiac is the daily blog of the Globe's Sunday Ideas section, covering news and delights from the worlds of art, science, literature, history, design, and more. You can follow us on Twitter @GlobeIdeas.
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Leon Neyfakh is the staff writer for Ideas. Amanda Katz is the deputy Ideas editor. Stephen Heuser is the Ideas editor.

Guest blogger Simon Waxman is Managing Editor of Boston Review and has written for WBUR, Alternet, McSweeney's, Jacobin, and others.

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Guest blogger Sarah Laskow is a freelance writer and editor in New York City. She edits Smithsonian's SmartNews blog and has contributed to Salon, Good, The American Prospect, Bloomberg News, and other publications.

Guest blogger Joshua Glenn is a Boston-based writer, publisher, and freelance semiotician. He was the original Brainiac blogger, and is currently editor of the blog HiLobrow, publisher of a series of Radium Age science fiction novels, and co-author/co-editor of several books, including the story collection "Significant Objects" and the kids' field guide to life "Unbored."

Guest blogger Ruth Graham is a freelance journalist in New Hampshire, and a frequent Ideas contributor. She is a former features editor for the New York Sun, and has written for publications including Slate and the Wall Street Journal.

Joshua Rothman is a graduate student and Teaching Fellow in the Harvard English department, and an Instructor in Public Policy at the Harvard Kennedy School of Government. He teaches novels and political writing.

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