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Published December 2015 | public
Journal Article

Was the Cambrian explosion both an effect and an artifact of true polar wander?


Charles Darwin suspected that the Cambrian "explosion" might be an artifact of fossil preservation. A more recent, initially controversial hypothesis that repeated true polar wander (TPW) triggered the Ediacaran-Cambrian explosion of animal life has been supported by numerous paleomagnetic and geochronologic refinements. These data imply ∼75° of TPW between 535 and 515 million years ago, coinciding with the paleontologically observed rise in metazoan diversity and disparity. We show here that this evolutionary trend is explained simply by the well known ecology-driven increase of diversity in low latitudes, coupled by other ecological effects as well as the enhanced deposition of sedimentary rocks during TPW-driven sea-level transgressions. During the Cambrian TPW event, Laurentia and parts of Gondwanaland moved into the equatorial zone while experiencing local TPW-induced transgressions; these areas dominate the paleontological record of the time. Although diversity might thus be considered partly artifactual, TPW acted on Cambrian biogeography to increase net diversity; and enhanced rates of origination and extinction also could increase disparity, especially if Early Cambrian TPW occurred at a time when genetic regulatory networks were critically poised for expansion and exaptation.

Additional Information

© 2015 American Journal of Science. David Evans, Matthew Powell, and Rob Van der Voo offered detailed critiques. The manuscript benefitted from discussions with Paul Asimow, Derek Briggs, Simon Darroch, Woodward Fischer, Taylor Kilian, Erik Sperling, and Jakob Vinther. RNM and JLK acknowledge support from NSF-EAR 1114432. JLK and TDR were also supported from NSF-EAR 0739105 and the NASA Exobiology program.

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