Developing a Synthetic Environmental Curve for the Phanerozoic: A Multiproxy Approach to the Origination Problem

One of the central problems of the paleobiology is to determine the role of environmental forcing in regulating origination, extinction as well as biodiversity through the Phanerozoic. Although several authors have argued that origination peaks were biological responses to the variation in a specific constraint – and individual components may have played dominant roles during specific intervals – not surprisingly the lack of a consistent correlation between a given environment control and the pattern of origination suggests the lack of a unique evolutionary driver. Here, we focus on the Phanerozoic pattern of origination derived from Sepkoski's (2002) compendium and compare it to an synthetic environmental curve (SEC) derived from temporal variations in sea level, mean global temperature, as well as mean global isotopic curves of δ¹⁸O and δ¹³C. Using this approach, we tested whether origination peaks corresponded more closely to the combination of physical and chemical changes than single components. Our results show that: peaks and troughs in both curves were very similar during Late and Middle Paleozoic, Mesozoic and Cenozoic. The dampened origination pattern associated with the Carboniferous and Permian periods no presented a strong correlation with the SEC. A possible explanation is that it records effects associated with biotic homogenization induced by Pangaea's formation, an element not incorporated in the SEC. Even though the correlation in the shape of both curves is strong, there is no correlation between the magnitude of the evolutionary and environmental change, potentially reflecting the need to introduce more physical and chemical components in combination with better temporally resolved data into the curves. These preliminary results suggest that the environmental conditions and evolutionary dynamics have been often linked in a less than straightforward relationship, but that the attempt to include a combination of variables suggests the potential to better explain origination over the past 545 Ma.