DIGITAL BIOLOGY

Be prepared for a fast ride through a dizzying digital universe driven by an amiable and enthusiastic guide.

Universes, actually. For what British computer scientist Bentley describes in seven chapters are digital systems he calls universes that model complex living systems. All such universes are characterized by rules that govern the behavior (“outcomes”) of their various parts, and all owe their existence to some external universe that created them. If you’re lucky, some of the rules will result in complex behavior and emergent properties (think language, or consciousness). A digital universe is a software program that comes into being by virtue of the (external) computer. Bentley takes readers along in baby steps to explain the essentials of their PCs: the memory, the arithmetic and logic unit, registers (for temporary memory storage), and input-output circuitry. Because he is particularly interested in evolutionary processes, his digital universes generally have rules of inheritance and sufficient variation in “offspring” to allow for selection to take place. As an example, he describes a furniture-design program in which the binary bits of 1s and 0s become genes that reproduce, following a genetic algorithm that defines what’s fit and what’s unfit; successive iterations of random gene crossings lead to the design of a neat coffee table. Things get more complex as Bentley reviews digital programs that model brains, social insect behavior, plant growth and form (including nature’s use of fractals and the Golden Section), immune systems, and development from embryo to adult. As a dividend for the reader, he summarizes what is known about the biology of the systems under discussion before launching his digital universes, making the point that the more biologists and computer scientists communicate, the better off science would be. While clearly a visionary, Bentley is humble enough to say that today’s models are often primitive and even quotes the Doubting Thomases.

Plenty of gee-whiz here to excite: a good bet for the nerds in your life.