- Web Hall 1100
Dr. Ross Mitchell, of Caltech and Yale, willl give this week's talk at Speakers Club entitled Did True Polar Wander Spark the Cambrian Explosion of Animals? The talk is at 2:00 PM on Thursday, March 31 in Webb Hall 1100.
Charles Darwin suspected that the Cambrian “explosion” might be an artifact of fossil preservation. A more recent, initially con- troversial hypothesis that repeated true polar wander (TPW) triggered the Ediacaran-Cambrian explosion of animal life has been supported by numerous paleomagnetic and geochrono- logic refinements. These data imply ~75 ̊ of TPW between 535 and 515 million years ago, coinciding with the paleontological- ly 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, cou- pled by other ecological effects as well as the enhanced deposi- tion of sedimentary rocks during TPW-driven sea-level trans- gressions. 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 di- versity might thus be considered partly artifactual, TPW acted on Cambrian biogeography to increase net diversity; and en- hanced 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 ex- pansion and exaptation.