See also: Why microbes are smarter than you thought
A BAG of biochemistry less than a millimetre across that spends most of its life attached to pond scum, the single-celled organism Stentor roeselii doesn鈥檛 sound impressive. Yet its behaviour is remarkably sophisticated. Squirt a jet of water at a Stentor and it will dive into its mucus holdfast, emerging cautiously soon after. But squirt another identical jet at the same Stentor and it ignores it.
Now squirt a jet of an irritant chemical and the Stentor will arch its stalk-like body out of the way, moving from side to side to avoid the stream. If this fails, it retreats. If the chemical is still there when it re-emerges, it retreats again. Eventually, it retreats with such force that it tears itself free and floats off in search of a new home.
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How can such complex behaviour arise in such a simple life form? This is the question that tackles with remarkable clarity and style in this excellent book. In a nutshell, his answer is that living cells, like the single-celled protozoa pictured, are chemical computers. They take information from the environment and process it to produce behavioural 鈥渙utputs鈥�. The processing units are proteins, which perform all the same operations as the logic gates of a computer. Inputs from the environment cause the proteins to flip shape, to aggregate, and to chemically modify other proteins in a cascade of information processing that sweeps through the cell until it reaches effector proteins that make the cell move or change shape.
This computation is the essence of 鈥渨etware鈥�, and of life. And when billions of chemical computers congregate into multicellular bodies, amazing things happen. Highly recommended.
Wetware
Yale University Press