so it even swayed the reluctant Delbrück.This was no small achievement, to be putalongside the simplicity and substantialbenefit to molecular biology of caesiumchloride gradients for ultracentrifugation.

Holmes suggests that the growing knowl-edge of the immense complexity of themechanism required for DNA duplicationmay be starting to crowd out mention of theMeselson–Stahl experiment. When Watsonand Crick suggested in 1953 that DNA replication might occur without the aid of a special enzyme, little did they foresee the complexity of the process, involving as it does not only DNA polymerase, but alsothe DNA helicases and primases, the proof-reading exonuclease, the sliding DNA clampand the Okasaki fragments — a multi-enzyme system that performs its task withremarkable fidelity. Nor, perhaps, did theyexpect the unwinding problem to resurfaceagain to challenge the double helix as late asthe 1970s.

This book joins a growing library of outstanding historical studies of modernexperimental biology that includes Hans-Jörg Rheinberger’s study of protein synthesisin the cell-free system, Toward a History ofEpistemic Things (Stanford University Press,1997) and Nicolas Rasmussen’s analysis ofthe adaptation of the electron microscopefor the study of the cell, Picture Control(Stanford University Press, 1999). Theirscholarship is impeccable and their analysesperceptive and revealing, not just of an agefast receding into the past, but of what BrunoLatour called “science in the making”. ■

Robert Olby is in the Department of the Historyand Philosophy of Science, University ofPittsburgh, Pittsburgh, Pennsylvania 15260, USA.

When ejaculatescollide…Sperm Competition and itsEvolutionary Consequences in theInsectsby Leigh W. SimmonsPrinceton University Press: 2001. 434 pp.£24.95 (pbk)

Michael T. Siva-Jothy

A million million spermatozoaAll of them aliveOut of their cataclysm but one poor NoahDare hope to survive.And among that billion minus oneMight have chanced to beShakespeare, another Newton, a new Donne— But that One was Me.

If Aldous Huxley had lived another sevenyears he might have amended his Fifth

Philosopher’s Song toinclude an extra competi-

tive dimension. Ever sinceAntoni van Leeuwenhoek first looked

at sperm under a microscope, and proba-bly long before, humankind has had aninkling of the wastage that occurs in malegametes.

But it was not until 1970 that a formaltheoretical framework, and some elegantempirical support for it, emerged. GeoffParker realized that when two or more males mated with the same female, selectionwould favour the evolution of male traitsthat gave one sperm-owner a paternityadvantage. This elegant and, with the benefitof hindsight, obvious concept opened thefloodgates to a sea of ideas and explanations.Suddenly post-copulatory guarding behav-iour made sense, we began to understand the causal basis of variation in hithertoignored aspects of reproductive behaviour,and we had an elegant explanation for a million million spermatozoa.

Parker’s theory had a profound effect onthe fledgling field of behavioural ecology —he laid a cornerstone that defined it and illustrated the value of combining model-ling, empiricism and a productive disregardfor disciplinary boundaries to address ques-tions about the how and why of evolution.Parker used insects as his model system: theywere particularly susceptible to this form of selection and were amenable to the combined physiological, anatomical andbehavioural studies that revealed the natureof the adaptations that resulted.

Having served his intellectual apprentice-ship in Parker’s laboratory and played a significant part in directing the field, LeighSimmons is better qualified than most todefine the current state of sperm competition.However, there are already three books thatexamine sperm competition in a range of taxa,

including insects,begging the ques-tions “why produceanother?” and “whyjust insects?” Simmonsargues that a comprehensivereview of our current knowledgeof the phenomenon in insects provides the broadest platform on which to base any understanding of sperm competition.To make this point he picks the field apart,paper by paper, and skilfully reassembles it around the important conceptual issues,thereby bringing sperm competition, rather than insect behavioural ecology, intocrisp focus.

Each chapter starts, when appropriate,with the theoretical basis for its sub-theme,followed by a well-structured review of theempirical work. For example, the chapteron behavioural adaptations to avoid spermcompetition begins with a very readable distillate of the theory and modelling ofmate-guarding. (Similar summaries of thecritical modelling and theory preface otherchapters and are a real bonus.) The chapterthen reviews the substantial literature onmate-guarding and alternative hypothesesfor this behaviour, before moving on to themore contentious subject of male matechoice. By leaving the open-ended subjectsuntil the end of their chapters, Simmonscontextualizes the new areas and so guidesthe reader to paths that have potential forfuture work.

This book is an excellent summary of a recent, important and relatively large addition to our understanding of evolutionand its consequences. It is an essential readfor anyone interested in the reproductivedeterminants of fitness. ■

Michael T. Siva-Jothy is in the Department ofAnimal and Plant Science, University of Sheffield,Sheffield S10 2TN, UK.

122 NATURE | VOL 417 | 9 MAY 2002 | www.nature.com

In sex? Sperm competition is crucial to understandingsexual behaviour in insects,such as these mealwormbeetles.

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