264-2 Co‐evolution of early Earth environments and microbial life: Extrapolating lessons learned up and down the time scale and to distant worlds

Abstract:

My journey in studies of ancient Earth and distant planets began with a dissertation deep dive into the anoxic modern Black Sea. My first significant step back in time logically landed in the Devonian for many reasons, including the importance of oceanic redox extremes and evolution at that time.  Any successes in these efforts are connected by a straight line to a wonderful collaboration with Brad Sageman and our colleague Dave Hollander. This was a special, formative time for me, elevated in many ways by a life-long friendship with Brad. He has taught me much about how to best integrate geochemistry within comprehensive studies of Earth's past and specifically the need for the full geologic context, and this boost led me naturally to complementary questions about the earliest chapters of Earth's coevolving life and environments.  Two records of Earth history capture this evolution of life and its co-evolving ecosystems with interpretable fidelity: the geobiological and geochemical traces preserved in rocks and the evolutionary histories captured within genomes. The earliest vestiges of life are recognized mostly in isotopic fingerprints of specific microbial metabolisms, whereas fossils and organic biomarkers become important later. Molecular biology provides lineages that can be overlayed on geologic and geochemical records of evolving life. All these data lie within a framework of biospheric evolution that is primarily characterized by the transition from an oxygen-poor to an oxygen-rich world. In this review presentation, I will explore the history of microbial life on Earth and the degree to which it shaped, and was shaped by, fundamental transitions in the chemical properties of the oceans, continents and atmosphere. I will examine the diversity and evolution of early metabolic processes, their couplings with biogeochemical cycles and their links to the oxygenation of the early biosphere. I will discuss the distinction between the beginnings of metabolisms and their subsequent proliferation and their capacity to shape surface environments on a planetary scale. The evolution of microbial life and its ecological impacts directly mirror the Earth’s chemical and physical evolution through cause-and-effect relationships. And all of this will build from the foundation of those earlier studies with Brad and the vital lessons learned.

Geological Society of America Abstracts with Programs. Vol. 58, No. 5, 2026

doi: 10.1130/abs/2026AM-21820

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