Mass extinctions and Earth system perturbations

Abstract

Earth presently boasts the unique claim of a planet harboring of life, including complex multicellular organisms (e.g., animals). Animals evolved over the past ~700 million years – about 10% of Earth history – and their evolutionary pathway has been turbulent. Biodiversity through time reflects a balance between species extinctions and new species origination; however, discrete intervals where extinction rates drastically exceeded species origination are recognized in the fossil record. These demarcate mass extinction events. The five largest mass extinctions correspond with evidence for major environmental perturbations, notably within Earth’s carbon cycle. These events not only demonstrate significant losses in diversity, but also were responsible for long-term ecosystem restructuring. Here I will discuss aspects of these ‘Big 5’ masses extinctions and the varying hypothesis for the driving mechanisms. I will present results from diverse data sets that aim to constrain the nature of environmental conditions, particularly changes in the ocean–atmosphere system and global climate, responsible for these extinctions. Earth is currently considered to be in the midst of the Big 6th mass extinction, and we have a lot to gain from the stories recorded in these ancient events.