CATS' PAWS AND CATAPULTS

Has human engineering improved on nature? A biologist answers the question. Biomechanics is the discipline that explores nature’s answers to what are essentially engineering problems. Vogel (Biology/Duke Univ.; Vital Circuits, 1992) doesn—t share the widespread assumption that human engineering is doomed to crank out clumsy imitations of what nature perfected eons before our race first chipped a stone into a cutting edge. For nature, sometimes to its disadvantage, must play by the rules of evolution, via natural selection; it is also restrained by geometrical and physical constants relating to growth and change, and it enjoys far less flexibility than do most human designers—nature cannot easily “go back to the drawing board” when an existing structure won’t serve its purposes. Humanity is better at making things big, while nature excels in compactness: No bird can match a jetliner for size, but 10,000 viruses could fit along the length of our tiniest machine. Vogel explains basic principles of engineering science, giving examples both from the familiar human world and from biological entities. The problems discussed include the ways a structure (a skeleton, a bridge, a tower, a wing) can be designed to resist various stresses; ways of generating power (steam engines, wind, and water mills); and ways of building up large structures from small (bricks, cells). Certain overarching verities emerge from this investigation: our preference for the right angle, where nature uses curves; our heavy dependence on the wheel, which is almost completely unknown in nature; and our favoring of sliding surfaces (metal hinges) over bending ones (sinew, muscle). Vogel is generally convinced that our technology surpasses nature’s evolutionary trial and error, but the reader is likely to emerge with greater respect for both. His well-written overview eyes the larger questions implicit in the subject.