Comparative Biomechanics: Life’sPhysical Worldby Steven VogelPrinceton University Press: 2003. 582 pp.$60, £39.95

Daniel E. Lieberman

Biology and engineering have a complex,often discordant, relationship. Living sys-tems are intrinsically messy, so most biolo-gists spend a lot of time analysing untidysubjects such as variation, ecological inter-actions and the multitudes of tangled,genetic, developmental and metabolic path-ways that organisms use. In biology, noise is often a kind of signal, and generalizableprinciples are hard to find. By contrast,engineers can take a more reductionistapproach to the world, deducing and testingthe inherent principles and mechanisms by which things fail, work or can be made to work.

Despite these differences, the two fieldsare vitally important to one another. Thephysical world poses many basic challenges,such as gravity, viscosity and pressure gradi-ents, to all living creatures,which in turn haveevolved an astonishing array of solutions.Many of these, such as paddles, valves andhydrostats, are so widespread that we rarelynotice them. Others perform so well that wemarvel at their superiority to human-madedevices. Did you know that fleas can acceler-ate at 2,000 m s�2 — that’s 20 times greaterthan the space shuttle during launch? Thatsilk has a tensile strength similar to that ofsteel? Or that oak trees can generate pres-sures of 500,000 Pa through evaporation?Nature is a pretty impressive engineer.

Biomechanics, the intellectually vibrantintersection of engineering and biology, isfundamental to our efforts to study every-thing from how proteins fold to how whalesfloat. More biologists ought to study engi-neering and vice versa. But the challenges ofintegrating these fields can be daunting, par-ticularly for students with a phobia aboutmaths,unhappy memories of physics classes,or simply the lack of an inspiring teacher.There are a handful of wonderful books onbiomechanics (many by R. McNeill Alexan-der), as well as more focused books onhuman, vertebrate or plant biomechanics,but no general textbooks. Now, thanks toSteven Vogel’s Comparative Biomechanics,we have a delightful and comprehensive text-book that is perfect for undergraduates andthose of us who need a refresher.

Vogel concentrates on three tasks. First,he reviews the basic principles of physics andbiology that underlie biomechanics, such

as units, forces, quantities and questions ofscale. Second, he reviews everything that an organism would ever want to know about fluids, focusing mostly on the ways in which plants and animals cope with thephysical properties of air and water. Here we encounter everything from solubility and surface tension to the all-importantReynolds number (the ratio of inertial forcesto viscous forces). And third, he reviews thematerial and structural properties of thesolid substances from which we are made.Ofparticular interest are the ways that plantsand animals generate and resist forces inorder to move or stay where they are.

Throughout the book, Vogel introducesthe formulae and principles that matter in aclear manner, and illustrates them with adizzying array of biological and physicalexamples. For instance, we learn how prairiedogs construct their burrows so that they are ventilated using the Bernoulli principle(as the speed of a gas or liquid increases, its pressure decreases); how basilisk lizards areable to run on water (and why a humanwould have to weigh just 4.6 g to accomplishthe same feat with our feet); how the penisinflates without losing girth (the trick is toavoid helical fibres); and why you shouldnever drink champagne from a plastic cup(you’ll lose more bubbles).

As these examples suggest, this book istremendous fun to read.Vogel writes with an

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effervescent sense of delight in his subject.The text is laced with wit and humour, andsprinkled with eclectic examples of nature’smany marvels. None of the fun, however,diminishes the clarity.

In Vogel’s world, plants and animalsreceive equal treatment in the context of thephysical problems they encounter. In thatsense, the comparative method he uses isbased on problems of physics,not evolution-ary relationships: tubes are treated as tubes,regardless of what kind of organism theyserve. Regrettably, this perspective leaves little room to explore key problems in evolu-tion.Vogel mentions only in passing variousdebates on topics such as constraints, adap-tation and the mechanisms by which organ-isms can or cannot alter in response tochanges in their environment. Of particularnote, he sidesteps the issue of optimizationand the extent to which natural selection drives organisms towards supposedly betterways to overcome the challenges posed bytheir particular environments.

I hope that Vogel will inspire a new gen-eration of college-level classes on biomech-anics. For many, this book will become astandard reference text, the sort of thumb-worn classic whose location on your shelfyou instinctively know. ■

Daniel E. Lieberman is professor of biologicalanthropology, Harvard University, 11 DivinityAvenue, Cambridge, Massachusetts 02138, USA.

Engineering for animalsBiomechanics explores natural solutions to the physical problems of living.

It’s a wrap: the flexibility and strength of spider silk spells the end for captured insects.

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