Inconstant Ancient Seas and Life's Path

摘要

What could the geophysics of Earth's deep interior have to say about the evolution of life? The two disciplines might seem to be a world apart, but a paper in this issue of Science (p. 1222) could help link them together. The new work confirms that the chemical composition of the world ocean has swung back and forth during the past half-billion years. Those oscillations, likely driven by the varying tempo of plate tectonics, might have helped trigger a number of important evolutionary events. Among them: the explosion of shell-bearing animals in the Cambrian period, the outpouring of chalk that created the White Cliffs of Dover, and the resurgence of massive coral reefs of recent geologic times.