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BENGTSON—ORIGINS AND EARLY EVOLUTION OF PREDATIONpreservation of planktic prey (Kitchell, 1983).Geochemical methods are becoming ever moresensitive, and the search for characteristicbiomarkers in Proterozoic rocks has started to yieldspectacular insights into the occurrence of organismsin sequences where a morphological record islacking (McCaffrey et al., 1994; Brocks et al., 1999;Summons et al., 1999). The recently realizedpossibility of analyzing isotopic ratios in individualProterozoic microfossils (House et al., 2000) maylet us characterize fossil organisms physiologicallyand thereby throw light on their mode of life. Theuse of lipid ratios in Pleistocene mollusc shells toidentify predators vs. suspension feeders (CoBabeand Ptak, 1999) is a particularly fascinatingextension of biogeochemical methods with greatecological significance, although the currentlyavailable analytical procedures are hardly applicableto the Proterozoic and Cambrian fossil record.Trace fossils are a direct reflection of behavior,and may represent the currently most profitableavenue for research into early predatory andantipredatory behavior. Whereas Cambrian tracefossils and bioturbation are almost ubiquitous, lateNeoproterozoic examples are comparativelyscarce, and reports of trace fossils older than 600Ma have yet to find general acceptance.Nonetheless, several reports of earlier trace-likefossils (e.g., Faul, 1950; Kauffman and Steidtmann,1981; Breyer et al., 1995; Seilacher et al., 1998;Rasmussen et al., 2002) have still to be given abetter explanation. Rather than being ignored asfreakish occurrences, they should be used as searchimages in a more concerted exploration forevidence of possible early adventures into motilemulticellularity and associated behavior.In the Cambrian, the prospects are quite goodfor a deepening understanding of the ecologicalinteractions shaping the biota. The main reason forthis is that the Cambrian is unusually blessed withfossil preservation lagerstätten. New Cambrian lifeforms are being reported from these each year, andwhen the basic morphologic and taxonomicinformation has been obtained, the foundation islaid for spectacular advances in the synecology andautecology of the Cambrian biota. With that, wewill also get a better handle on the ecology of theCambrian explosion itself.REFERENCESABRAMS, P. A. 2000. The evolution of predator-prey interactions: theory and evidence. Annual Review of Ecologyand Systematics, 31:79–105.AGRAWAL, A. A., C. LAFORSCH, AND R. TOLLRIAN. 1999. Transgenerational induction of defences in animals andplants. Nature, 401:60–63.ALLISON, C. W. 1981. Siliceous microfossils from the Lower Cambrian of Northwest Canada: possible source forbiogenic chert. Science, 211:53–55.ALLISON, C. W., AND J. W. HILGERT. 1986. Scale microfossils from the Early Cambrian of Northwest Canada.Journal of Paleontology, 60:973–1015.ALPERT, S. P. 1977. Trace fossils and the basal Cambrian boundary, p. 1–8. In T. P. Crimes and J. P. Harper (eds.),Trace fossils 2. Geological Journal, Special Issue.ALPERT, S. P., AND J. N. MOORE. 1975. Lower Cambrian trace fossil evidence for predation on trilobites. Lethaia,8:223–230.AWRAMIK, S. 1971. Precambrian columnar stromatolite diversity: reflection of metazoan appearance. Science,174:825–827.AWRAMIK, S. M., AND J. SPRINKLE. 1999. Proterozoic stromatolites: The first Marine Evolutionary Biota. HistoricalBiology, 13:241–253.AYALA, F. J., A. RZHETSKY, AND F. J. AYALA. 1998. Origin of the metazoan phyla: Molecular clocks confirmpaleontological estimates. Proceedings of the National Academy of Sciences, USA, 95:606–611.307