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The Origins of Order (Oxford Univ. Press, New York, 1993). Acknowledgements Y.V.d.P. acknowledges support from the IUAP P6/25 (BioMaGNet). A.M. thanks the Deutsche Forschungs￾gemeinschaft, University of Konstanz and the Institute for Advanced Study Berlin for support. S.M. is a fellow of the Fund for Scientific Research — Flanders (FWO). We thank two anonymous reviewers for valuable comments and suggestions and apologize to those whose work could not be cited because of space limitations. FURTHER inFORMATiOn van de Peer laboratory homepage: http://bioinformatics.psb.ugent.be Meyer laboratory homepage: http://www.evolutionsbiologie.uni-konstanz.de All links ARe Active in the online pdf Pers P ectives 732 | oCToBEr 2009 | voluME 10 www.nature.com/reviews/genetics © 2009 Macmillan Publishers Limited. All rights reserved