- Cats’ Paws and Catapults: Mechanical Worlds of Nature and People*
On first thought, the idea behind this book is a very odd one. On second thought, what’s odd is that no one has come up with it before. The idea is to compare how nature engineers with how people do. How do nature’s products—living organisms—work mechanically, and how do they differ, in construction and functioning, from the things we make? And what do the similarities and differences tell us, about both nature and ourselves?
Steven Vogel, a professor of biology at Duke University whose particular field is biomechanics, gives an engrossing tour through a welter of fascinating [End Page 652] small complexities. For instance, in a chapter on rigidity he explains how nonmetallic man-made materials avoid catastrophic cracking by breaking up the concentration of force that a crack represents through the use of composites; they interrupt the stiff strength of an easily cracked material with the load-spreading give of a softer one. Styrofoam interrupts brittle plastic with pockets of air; fiberglass, stiff glass with soft glue; particle board, wood chips with binder. Nature does the same thing. Wood combines cellulose and lignin, which is essentially glue; mollusk shells mix calcium and protein. And, the author adds in his entertaining fashion, “even your teeth are composites of mineral and protein; when teeth are drilled, burning protein makes the sulfurous smell” (p. 123). Moreover, nature designs composites just as nimbly as we do. “Not only does wood vary from one kind of tree to another, but the wood of a tree’s roots has very different properties from the wood of its trunk” (p. 123).
This is all absorbing to read, but what does a book full of it add up to? In the last chapter, the author offers a long list of basic differences between nature’s and man’s technologies. Certain basic materials and forms in our technology never, or almost never, show up in nature—metals and wheels, for instance. We use flat surfaces more; nature prefers a curve. Our corners are abrupt; nature’s are rounded. Nature concerns itself more with strength than with stiffness; we do the opposite. Nature’s favorite hydrostatic or aerostatic fluid is water; we like air and gases. Our factories are much bigger than what they make; nature’s are the opposite. We design for minimal maintenance; nature for constant maintenance. And on and on. But still, what does it add up to?
“This view of nature as a technology,” Vogel ends up saying, “has provided an unusual perspective on the world around us” (p. 309). Certainly true. But it noticeably fails to reveal any technologies we can but haven’t already profitably duplicated. If anything, the opposite: “I began with statements extolling the superiority of nature. In a sense this entire book is my skeptical response. Sure, nature is wonderful. But bear in mind what we do that she doesn’t: However they came about, the unique achievements of our species deserve full appreciation. Metallic materials, ropes of short fibers, woven fabrics of crossed threads, the wheel and axle, thermal expansion engines, fast surface ships, electrochemical energy storage, lighter-than-air aircraft—humans, our engineers in particular, have made extraordinary things” (pp. 310–11).
The extraordinariness of nature’s technologies, of course, is that they are all grown rather than made. They come from incrementally evolved genetic recipes, not blueprints. They change in size and sometimes function within the individual, and they transmogrify utterly over generations. The author alludes to this miraculousness, observing, for instance, that “future benefit is something evolution knows nothing about; she has precious little venture capital” (p. 127). But perhaps because he is innately very modest, [End Page 653] or more likely because he feels no need to beat what he probably considers a dead horse, Vogel does not trumpet the book’s strongest and broadest message of all: It is as powerful and unassailable an argument...