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Today’s lecture on the Ocean Anoxic Events (OAE’s) and the geochemistry of extinction begged the question: who controls the Earth?  Are the combined anoxic events and associated C13 events imply that geology – for example, magmatism – is a driver of primary production, or are the events evidence of the evolution of key characteristics in phytoplankton and other organisms?

This is an important question for my work on the Proterozoic, especially the Neoproterozoic.  During the Paleoproterozoic and Neoproterozoic, large d13C isotope excursions are seen in both the organic carbon and carbonate records.  But do these reflect novel characteristics of organisms – for example, increased sinking of organic matter in the form of feces, or the rise of oxygenic phototrophs – or are the organisms being driven by forces outside their control?

Generally, I support the idea that the biology of Earth is at the mercy of Earth’s geology – that major events in the evolution of life and the chemistry of the oceans was driven not by new characteristics in the constituent organims, but by things such as magmatism and climate.  However, this is obviously a heuristic argument – climate, for example, is driven not only by the release of CO2 and methane from hydrothermal vents, but also by the amount of CO2 sequestered by organisms dying, sinking and being buried in the ocean.

So I’m leaving this question open to others: who is the real strongman of Earth?  Biology or geology?

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