Precambrian Earth: Co-evolution of life and geodynamics
Francès Westall, Shuhai Xiao
Abstract
• Early, rapidly diversification and spread of anaerobic life. • Preservation of early life largely through silicification. • Evolution of oxygenic photosynthesis related to geodynamics and geochemistry. • Global development of stromatolites after GOE and glaciation. • Start of biogeodynamic cycle in the Neoarachaean-Palaeoproterozoic. • Importance of carbonate as of the Meoarchaean. • Timing of emergence of eukaryotes unknown • Three stages of eukaryote development in the Proterozoic The Precambrian covers 80% of the history the Earth. In this timespan, the Earth developed from an anaerobic planet to the oxygenic planet dominated by Wilson-style plate tectonics that we know today. Concomitant with geological evolution, life emerged and evolved, gradually colonising all known aqueous habitats. Until the Palaeoarchaean, life was largely dominated by its geological environment. However, as of the Mesoarchaean, when there were major changes in geodynamics leading to continental erosion and runoff of essential nutrients, the effects of life started to impinge on the geological environment. The interaction of life and Earth was and is reciprocal, hence the term biogeodynamics. In this review, we trace the evolution of geology and life in parallel, thus highlighting the gradual buildup of the importance of life on terrestrial processes, and the importance of changes in the geological environment on the evolution of life. We do not attempt to make an exhaustive review of all the occurrences of life in the Precambrian but use selected examples to illustrate key events and changes. We conclude by addressing certain aspects of the evolution of life that require more in-depth study and show how the finding of extra-terrestrial life would advance our understanding of life on Earth.