Emi’s fate, our fateA stark warning that overpopulation is threatening global biodiversity.

The Future of Lifeby Edward O. WilsonLittle, Brown: 2002. 244 pp. £18.99 (UK);Alfred A. Knopf: 2002. 256 pp. $22 (US)

Paul R. Ehrlich

Edward O. Wilson is a member of an impor-tant but very rare species: the world-class scientist who is also a great writer. The pro-logue to The Future of Life, written as a letterto Henry David Thoreau, the “foundingsaint of the conservation movement”, illus-trates his graceful style beautifully. Fromcontemplating Walden Pond in Massachu-setts, Wilson moves on to consider the stateof global biodiversity. He accurately and passionately tells the story of the disappear-ance of many of the only living beings weknow of in the Universe — key componentsof humanity’s natural capital.

The Future of Life outlines for the non-scientist the causes of the extinction crisis,explains the stake that humans have in it,and analyses solutions — some of which are already being put into practice. Evenbiologists who are familiar with much of the book’s content will find it a wonderful read, full of interesting details. Wilson has a splendid feel for organisms, whether he istelling the story of Emi, one of the remaininghandful of Sumatran rhinos, or describingthe intricate biological community thatcould be found in a rotting log in a vacant-lot ‘micro-reserve’.

I was especially pleased to see a clearstatement that human population growthplays a key role in the loss of biodiversity and general degradation of the environ-ment. A misguided political correctness has prevented many scientists and environ-mentalists from stating the obvious — thatoverpopulation of Homo sapiens is a criticalelement both in causing environmentalproblems and in exacerbating their conse-quences. The more people there are, themore greenhouse gas is emitted into theatmosphere, all else being equal. The moregreenhouse gas, the greater the chances ofrapid climatic change, which could stressagricultural systems. The more people there are, the harder it will be for thosestressed systems to feed everyone.

Wilson is direct. Speaking of the UnitedStates, “whose citizens are working at a furi-ous pace to overpopulate and exhaust theirown land and water from sea to shining sea”,he paints a picture completely at odds withthe uninformed view of most Americans.

He also briefly addresses a less-recognizedcompanion problem to overpopulation:overconsumption. Writing to Thoreau, he

says: “We are inside a bottleneck of over-population and wasteful consumption” (myemphasis). The consumption multiplier(which in a sense makes the United States the most overpopulated nation) is not a popular topic in consumer societies. Appealsfor conservation and efficiency often fall ondeaf ears, as does talk of moving “down thefood chain to a more vegetarian diet”. Butsuch talk, and discussions of consumptioncontrol in general, are badly needed. As achocoholic and pilot, I know the challengespersonally. World-class economists andecologists are beginning to tackle the diffi-cult problems of defining overconsumption

and dealing with it; Wilson’s book could helpto move the issue towards the political agenda. We already know what needs to be done to promote gradual populationreduction. Maybe there will be some “con-sumption condoms” in our future.

It is incumbent on reviewers to say whatthey didn’t like about a book, but that is atough assignment in this case. Wilson and Idiffer mostly in matters of emphasis in areasthat are far from settled. I am less sanguinethan he is about the theoretical ability of theEarth in 2100 to support 10 billion people at a “decent standard of living”, and believethat the problem of population extinctions

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book reviews

Paradise lost? The Earth’s rich biological heritage is at risk from human population growth.

© 2002 Macmillan Magazines Ltd

(which degrade critical ecosystem services)deserves more attention.

On the positive side, I think that the development of countryside biogeography as a framework for enhancing the preser-vation of biodiversity in human-dominatedlandscapes deserves attention alongside pros-pects for establishing large-scale reserves,which Wilson discusses very thoroughly. On a separate issue, I’m more sceptical about heritability estimates churned out by behavioural geneticists (often based onbadly analysed twin studies) for such attri-butes as proneness to agoraphobia and fearof snakes. But these are trivial matters compared to the magisterial sweep of TheFuture of Life, and I find myself in total agreement with its major points.

Wilson was recently attacked viciously inthe pages of The Economist. He was critical ofBjørn Lomborg’s anti-environmental bookThe Skeptical Environmentalist, which themagazine and Cambridge University Presshave been heavily promoting. In my view,Wilson had accurately pointed out that busyscientists were having to waste a hugeamount of time replying to the book’s dis-tortions. The Future of Life, by coincidence, is Wilson’s perfect response. It clearly lays out the reasons for his deep concern for thehuman future (shared by the vast majority of his colleagues) and why he thinks that scientists and society have no time to waste. It also reveals him to be a thoughtful, caring, life-loving human being. ■

Paul R. Ehrlich is in the Department of BiologicalSciences, Stanford University, Stanford, California94305, USA.

From E. colito elephantsGenes and Signals by Mark Ptashne and Alexander Gann Cold Spring Harbor Laboratory Press: 2002.208 pp. $59, £43 (hbk); $39, £28 (pbk)

Kevin Struhl

The regulation of gene expression is a funda-mental aspect of biological phenomena suchas the response to environmental conditions,the development of multicellular organisms,morphology and disease. Gene regulatorypatterns are extraordinarily diverse andcomplex, yet the regulation of each gene is precise with respect to when and how muchexpression occurs. Gene regulation is alsoremarkably flexible, both to rapidly alter theconstellation of genes expressed in responseto new conditions, and to accommodate evolutionary demands. At most, a few thou-sand proteins account for the complexityand precision of gene regulation in humans.How is this accomplished?

Molecular studies of gene regulation were

pioneered by François Jacob and JacquesMonod in the early 1950s. By the mid-1960s,three basic types of specific DNA sequencethat determine the level of expression underparticular physiological conditions weredefined in the bacterium Escherichia coli.Such regulatory DNA sequences turn out tobe specific binding sites for RNA polymer-ase, repressor proteins and activator pro-teins. Regulation of an individual gene isdetermined by the quality of its polymerasebinding site, the particular activator and/orrepressor proteins that bind in the vicinity of RNA polymerase, and the physiologicalconditions that modulate the function of the activators and/or repressors.

Monod once wrote that “anything that is true of E. coli must be true of elephants,except more so”. In a lucid and provocativebook, Mark Ptashne, a leading figure in thefield for nearly 40 years, and Alexander Gann argue for a unifying principle of generegulation that centres on the concept of regulated recruitment by means of adhesiveinteractions between proteins. They go on to argue that such regulated recruitment is a general strategy used by many other biological mechanisms involving enzyme specificity, regulatory precision and evolu-tionary flexibility.

Using a few well-chosen examples,Ptashne and Gann first describe three distinctmechanisms of transcriptional activation inbacteria. In one mechanism, DNA-bindingactivator proteins stimulate gene expressionby recruiting RNA polymerase to the pro-moter sequences that lie just upstream of the gene. Recruitment is mediated by short‘adhesive’ surfaces between the activator and polymerase, and the adhesive proper-ties per se are sufficient for activation. In a second mechanism, the activator induces a

confor-mationalchange in an inactive polymerase alreadybound at the promoter, thereby stimulatingtranscription. And in a third mechanism, theactivator induces a conformational change in the promoter, effectively changing it froman inactive to an active form. This section ofthe book presents the key experiments andarguments for these mechanisms in a mannerthat is exceptionally lucid and beautifullyillustrated. It is understandable to the non-expert, for whom it was intended, and is a ‘must read’ for anyone interested in gene regulation.

Armed with these lessons from bacteria,Ptashne and Gann consider yeast, a single-celled eukaryote, and conclude that acti-vation occurs by regulated recruitment ofthe transcription machinery (which containsmore than 50 proteins and so is much more complex than bacterial polymerases).Again, the authors use the device of a well-chosen example for clarity, the brief is convincingly argued, and the end result is illuminating to both the expert and thenovice. The emphasis on regulated recruit-ment is important for the overall theme ofthe book, and it is certainly true that thismechanism predominates in yeast cells.

However, in emphasizing the funda-mental similarities between bacteria andeukaryotes, Ptashne and Gann have made an unconventional choice in classifyingchromatin-modifying activities as part ofthe transcription machinery. Chromatinand chromatin-modifying enzymes affectall eukaryotic processes involving DNA, and are typically considered as part of theDNA template, rather than the transcrip-tion machinery. So although activators andrepressors use adhesive surfaces for regu-

book reviews

22 NATURE | VOL 417 | 2 MAY 2002 | www.nature.com

The same, only more so: gene regulation is similar for organismsranging from the elephant to the bacterium Escherichia coli.

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© 2002 Macmillan Magazines Ltd