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attention a ‘forgotten woman in a man’s world’is passé in the early twenty-first century. How-ever, I think the author is justified on othergrounds. With almost all of Bate’s personalrecords, such as diaries or photographs, havingbeen lost, destroyed or perhaps never made,Shindler has focused instead on the work of a scientist of considerable ability, originalityand resourcefulness. Perhaps it is today’salmost voyeuristic obsession with the analy-sis of motives and feelings, and the cult of personality, that leads us to expect a biographyto address such issues — especially as the

subject is female, and therefore ‘ought’ to haverecorded her innermost feelings. I certainlydon’t keep any such diaries, and I wonder howmany of my fellow scientists do.

In this biography, then, we are dealing firstand foremost with a scientific record. In theend, it is the results of her research — the newspecimens, species and their descriptions —that stand the test of time. I am grateful toShindler for bringing Bate and her work to my attention. ■

Jennifer Clack is at the University Museum ofZoology, Downing Street, Cambridge CB2 3EJ, UK.

A Stone Age greenhousePlows, Plagues and Petroleum: HowHumans Took Control of Climateby William F. RuddimanPrinceton University Press: 2005. 272 pp.$24.95, £15.95

Robert J. CharlsonThe activities of Stone Age farmers may havealtered Earth’s climate. This is the exciting but controversial theory conveyed by palaeo-climatologist William Ruddiman in his well-written book Plows, Plagues and Petroleum.

I am not a climatologist, but my work onatmospheric chemistry, aerosols and cloudphysics relates to Ruddiman’s analysis ofEarth’s climate over the past few millennia.Aerosols and clouds must be included in anyanalysis of palaeoclimate because they are sovariable and exert such a powerful influenceon the albedo of the planet. It cannot beassumed that they remained constant over thistime. I strongly support Ruddiman’s view thatfitting all these pieces together to figure out the key cause-and-effect relationships “makesstudying climate history fun”.

Ruddiman’s book is unusual because he can-didly describes his main ideas as a thesis ratherthan as fact, and states that they are currentlybeing debated in refereed publications. Thishigh level of candour will certainly be appreci-ated by scientists, and the book’s descriptiveanalogies and lack of jargon make it accessibleto the lay reader as well.

The book starts with the importance of climate to human history, the basic science of climate, the connections between Earth’sorbit and climate, and the modulation of iceages, monsoon circulations and climate, with“nature in control”.

The main thesis then emerges, with adescription of the inexorable changes imposedby humans on the chemical composition ofEarth’s atmosphere. Starting with Ruddiman’sstrongest scientific argument, the increase ofthe greenhouse gas methane about 5,000 yearsago is attributed to Stone Age farming. Simplecalculations of the amount of methane gener-ated per person by flood irrigation, animal

husbandry and biomass burning show emis-sion rates high enough to explain the methanedata obtained from ice cores.

Other population-based estimates for theemission of carbon dioxide, another green-house gas, show that over a period of severalthousand years, enough biomass combustioncould have occurred during land clearing toincrease the concentration by the observedamount, 40 parts per million. Stone Agehumans apparently began burning forestsabout 8,000 years ago, which fits with the timeseries of carbon dioxide data.

Moving from the data-based analysis of rising levels of methane and carbon dioxide tothe tentative business of climate forecasting,Ruddiman then asks: “Have we delayed aglaciation?” He thinks we have, arguing thatthe stability of the climate over the past 10,000 years “may have been an accident”. Thewarmth of the past several thousand years“stems from a colossal coincidence: a naturalcooling” that was “offset by a human-inducedwarming”.

Then, in what almost seems to be an after-thought, the small ‘wiggles’ in the carbon dioxide record and a decrease in the rate of itsincrease over the past 2,000 years are inter-preted to have been caused by the decimation

of human populations in epidemics and pan-demics. Smaller populations produced lesscarbon dioxide, adding yet more variables tothe study of palaeoclimate.

The main part of the book concludes withthree chapters on the nature of climate in afuture with “humans in control”. Ruddimanprovides a vivid description of the immensityof human influence on the climate and on theenvironment in general. The growth of green-house gases is singled out, with carbon dioxideand methane being dominant. The paradoxi-cally small observed temperature increase inthe industrial period (about 0.6 �C), comparedwith the larger rise of 0.8 �C caused by previ-ous human activity, is attributed to a delay inclimate response and to cooling factors gener-ated by humans, such as sulphate aerosols.

Current global warming is then analysedover a shorter time scale (centuries) by meansof uncertain estimates of the future rate of car-bon dioxide and methane emission by humanactivities. This shorter-term analysis is then setin the context of the distant past (with naturein control) and for several centuries in thefuture (under human influence), all properlylabelled as uncertain.

An epilogue completes the book, in whichRuddiman presents his own views on theissues of climate change. He decries the habitin the press of wanting “clever, crisply phrasedsound bites” and he laments the polarizationregarding global warming. He calls for recog-nition of the underlying reality that “draconianeconomic sacrifices” will be needed, and thatthis should put the global-warming debate “in a clearer perspective”. So ends an excellentbook summarizing and placing in context theage-old influence of humans on atmosphericcomposition, climate and global warming.

However, just as it is difficult to prove thatEarth’s warming over the industrial period hasbeen caused by the emission of greenhousegases through human activities, it is also diffi-cult to prove that Stone Age farming caused alack of cooling thousands of years ago. Thedebates about the causality of both present-daywarming and the warming needed in the pastto delay an ice age can be summarized brieflyin terms of the concept of climate forcing, theimposed change in energy balance. For causal-ity of global warming to be demonstrated,three interconnected premises must hold: theanthropogenic global forcing must be positiveand substantial in magnitude; the temperaturechange must be positive and beyond the rangeof natural variability; and the former must bethe cause of the latter.

If Ruddiman used the concept of forcing tostrengthen and refine his thesis, he couldaddress more specifically the uncertainties in assigning the causality of temperatureincreases to Stone Age agronomists. He couldfind further reasons for the higher sensitivityof temperature to early changes in methaneand carbon dioxide levels. He would have toconsider smoke from biomass burning as a

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cooling factor — might it have played a role incausing the little ice age?

The debate continues among climatologists,but it would seem that Ruddiman must be atleast partly correct: there can be no questionthat Stone Age farmers added methane andcarbon dioxide to the atmosphere, but howmuch and when? The debate, which seems to centre on the interpretation of details of

temperature inferences from isotopic recordsin sediments and ice cores, cannot disguise thefact that levels of both methane and carbondioxide began to increase long before the onsetof industrialization. ■

Robert J. Charlson is in the Department ofAtmospheric Sciences and the Department ofChemistry, University of Washington, Seattle,Washington 98125, USA.

fur on a hunting expedition. If he had copiedthe bur–fur attachment exactly, he would haveput hooks on only one of the surfaces. Instead,he put hooks on both. Biomimetics does notimply slavish copying, merely the applicationof a principle from nature. For this reason,Peter Forbes prefers the term ‘bio-inspiration’.His new book about it, The Gecko’s Foot, isdesigned for general readers, who will needvery little prior scientific knowledge.

Surprisingly, Forbes starts his book with a discussion of scale. He argues that there is a range of sizes to which we are relatively blind. We can see things that are as small as a micrometre with optical microscopes, andchemistry has taught us a great deal aboutatoms and molecules of the order of a nano-metre. He argues that the gap between thoselimits is our blind zone, and is especiallypromising for biomimetics.

Forbes supports this argument with anexcellent example, a recently developed paintinspired by lotus leaves, which stay clean evenin the muddiest water. Wilhelm Barthlott, a

Sticking with natureThe Gecko’s Foot. Bio-inspiration:Engineered from Nature.by Peter ForbesFourth Estate: 2005. 272 pp. £20

R. McNeill AlexanderBiomimetics is the application of ideas fromnature in engineering. At first sight, it seems a promising approach: evolution by naturalselection is extremely effective, and designerscan surely learn from its solutions. But so far,biomimetics has not achieved very much. Asrecently as 2003, Julian Vincent, professor ofbiomimetics at the University of Bath, UK, andone of its keenest proponents, wrote that “theonly successful examples I know of are Velcro(1955) and the Anglepoise lamp”.

I would discount the Anglepoise lamp. Itssprings will support it in any position, much asthe elastic ligament in a cow’s neck supports itshead, but I know of no evidence that the lampdesigner knew about the cow. Velcro is moreconvincing. Its inventor, George de Mestral,got the idea from burs that stuck to his dog’s

botanist at the University of Bonn, Germany,discovered that these leaves are covered in tinyhydrophobic tubercles, in the blind-zone rangeof sizes. On this surface, water forms almostspherical drops, and rolls off as if from a duck’sback, carrying dirt away with it. (The duck’sback works on the same principle.) Barthlottpersuaded a paint company that the lotuseffect, as he called it, had commercial poten-tial, and they developed a paint for the outsideof buildings. It looks like ordinary paint buthas a silicone surface that is rough in the blind-zone scale. Rain keeps it beautifully clean.

Forbes continues with other examples. Thegecko’s foot, which gives his book its title, iscovered with a carpet-like pile of hairs. Theend of each hair has many branches a few hundred nanometres across. These hairs makesuch close contact with the surfaces on whichthe lizard walks that they adhere by inter-molecular attraction (the van der Waalseffect). This lets the gecko climb walls andeven run across the ceiling. Adhesive tapeworking on the gecko principle has been madebut not yet commercially developed.

Forbes discusses other examples in the sizerange that he thinks so promising, includingthe multilayer reflectors in the wings of iridescent butterflies and the self-assemblingproperties of bacteriophages but, as with thegecko, these are potential rather than realizedcommercial applications. He discusses somelarger-scale effects, including the aerodynam-ics of insect flight and the folding pattern thatenables a large leaf to be opened from a slenderbud, but these are also of possible future valuerather than current successes.

Forbes frankly admits that biomimetics hashad few triumphs so far. He tells us in his finalchapter: “I have written about science andtechnology on the hoof because this is a newscience and success is a matter of decades ofwork. Rather than wait until some of thesetechnologies have become commonplace, I have tried to capture the Wordworthian ‘bliss-it-was-in-that-dawn-to-be-alive’ momentof seeing what was, until 15 years ago, a wholly unexpected science taking shape beforeour eyes.”

There is a great deal of interesting and unfa-miliar material here, but I found some of thescientific explanations unsatisfactory. To quoteone example, in the explanation of the lotuseffect, the statement that “water sits on thepoints of the bumps, with the compression of the air in the cavities giving extra buoyancy”is misleading: the effect depends on contactangles, not air pressure and buoyancy. On the other hand, an admirably comprehensive set of notes directs readers to the primary scientific literature. The general readers forwhom this book is intended will enjoy it, and it will give them some appreciation of afascinating field. ■

R. McNeill Alexander is in the Faculty ofBiological Sciences, Miall Building, University of Leeds, Leeds LS2 9JT, UK.

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