A review of The Tinkerer’s Accomplice: How Design Emerges from Life Itself. By J Scott Turner. Cambridge (Massachusetts): Harvard University Press. $27.95. ix 282 p; ill.; index. ISBN: 0-674-02353-6. 2007. This is an inspiring volume about the emergence of “designedness” in biological systems. It will make readers think, particularly because it deviates from dogma and openly asks questions about the principle of design generation in nature. The “tinkerer” in the book’s title is Darwinism. The “accomplice” is the something else that is needed. Turner calls it “intentionality” and defines it as “actions that are explicitly geared toward creating some future or other abstract state” (p 200). He does not say what universal features the future state should have. He argues that biologists must come to grips with the fact that tinkering alone does not explain design, or self-organization, or self-optimization. I agree, and so do growing numbers of biologists, physicists, and engineers. For example, see the thick “animal design” issue of the Journal of Experimental Biology (Hoppeler and Weibel 2005). Turner’s book is rich in examples and illustrations that support this argument (muscle weave, blood circulation, smart bones, efficient digestive tube, and vision, among others). This volume is excellent because it triggers new questions and cements new connections. The reason is that its theme has a lot in common with constructal theory, which is a theory of physics (e.g., Bejan 1997, 2000; Bejan and Lorente 2006; to read more, see www. constructal.org). The author devoted pages 58 to 63 to this theory with the demonstration of how a tree-shaped flow structure (river basin, lung, blood, lightning, cooling a heat-generating volume) is deducible from principle. In constructal theory, the principle is known as the constructal law of generation of configuration as a physics phenomenon: “For a finite-size flow system to persist in time (to live), it must evolve in such a way that it provides easier access to the imposed (global) currents that flow through it” (Bejan 1997:807). This law accounts for the time arrow of the physics phenomenon (the “animated movie”) of configuration generation and evolution. A time arrow is also implicit in Turner’s use of the concept of “intentionality.” Another similarity is the author’s use of the concept of homeostasis, or the action of Bernard machines and Aristotle’s equipoise. In constructal theory, this is the “optimal distribution of imperfection”—i.e., the balance between highly dissimilar flow resistivities, such as the balance between the fast (river channel, bronchial airways) and the slow (hill slope seepage, diffusion in the alveolar tissue) in the design of river basins and lungs with space as a constraint. Turbulent flow is another example of the allocating of fast
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May 16, 2012
H Kobayashi + 3
Open Access