Claremont Discourse Lecture: "The Cambrian Explosion: The Burgess Shale and the Flowering of Complex Life on Earth"

Prof. Robert Gaines, Geology Department, Pomona College
Wednesday, February 6th, 4:15 PM, Founders Room, Honnold/Mudd Library

More than half a billion years ago, Earth experienced a series of radical changes that permanently transformed the planet. These events, driven by evolutionary innovations, were of sufficient magnitude that geologists divide Earth's entire 4.6 billion year history into two fundamental parts, the Precambrian and Phanerozoic Eons. The "Cambrian Explosion" of life that defines this transition is marked by the origin and rapid expansion of complex life, the shift from an entirely microbial world to one dominated by multicellular organisms, the origin of animals, and the advent of predation and complex ecosystems. Our best record of this event comes from the Burgess Shale of British Columbia and a handful of similar geologic formations that preserve extraordinary fossil assemblages. Whereas the fossil record is almost exclusively comprised of mineralized "hard parts", primarily shells, teeth, and bones, the Burgess Shale and other deposits like it also preserve the "soft", labile tissues of the earliest animals, including guts, gills, musculature and eyes, and provide the most valuable paleontological record of the sudden rise of the animals. Pomona Geology professor Robert Gaines will provide an introduction to the Cambrian Explosion and to his ongoing field research with international teams in British Columbia, China, Morocco and elsewhere that have offered new insight into the causes of this long-enigmatic and singular transition in the history of life on Earth.


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