Dynamical Change in Global Biogeochemical Cycles Accompanying Early Animal Evolution

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0420592RothmanThis project seeks to identify and quantify the ways in which the evolution of early animal life influenced, and was influenced by, changes in global biogeochemical cycles. The time interval of interest ranges roughly from 500-600 million years ago; it began with the earliest known microscopic animal fossils and culminated with the rapid diversification of marine animals known as the "Cambrian explosion." Recent work based on analyses of geochemical data indicates that these evolutionary changes were accompanied by a major dynamical transition in the global carbon cycle. This transition should have been accompanied by increased oxygenation of the oceans. Because the evolutionary innovations themselves should have been favored by increased oxygen concentrations, the Cambrian explosion may have been both a cause and an effect of changes in global biogeochemical cycles.This project will test the validity of these hypotheses by combining efforts in biogeochemical theory, geologic field studies, organic geochemistry, and evolutionary biology. A new theoretical formulation of the global carbon cycle provides a means of relating changes in the carbon cycle to changes in the isotopic compositions of specific organic compounds that can be extracted from ancient sediments. Changes in biogeochemical cycling inferred from analysis of the geochemical data will then be related to the fossil record of animals and the evolution of algal and other protistan microfossils.The subject is central to both evolutionary theory and Earth history. The work seeks to specify, for one of the most important intervals in the history of life, how and why environmental change interacted with changes in the biosphere. It promises to show us the extent to which global biogeochemical cycles are related to specific aspects of the biosphere they support.The project also includes efforts to improve education in evolution, Earth history, and biogeochemical cycles, with emphasis on their joint interaction. Exhibits at two museums will contribute to the education of the general public. The interdisciplinary nature of the project will also offer unique opportunities for the education of graduate students.