The evolution of complex life and the stabilization of the Earth system

Abstract

The half-billion-year history of animal evolution is characterized by decreasing rates of background extinction. Earth's increasing habitability for animals could result from several processes: (i) a decrease in the intensity of interactions among species that lead to extinctions; (ii) a decrease in the prevalence or intensity of geological triggers such as flood basalt eruptions and bolide impacts; (iii) a decrease in the sensitivity of animals to environmental disturbance; or (iv) an increase in the strength of stabilizing feedbacks within the climate system and biogeochemical cycles. There is no evidence that the prevalence or intensity of interactions among species or geological extinction triggers have decreased over time. There is, however, evidence from palaeontology, geochemistry and comparative physiology that animals have become more resilient to an environmental change and that the evolution of complex life has, on the whole, strengthened stabilizing feedbacks in the climate system. The differential success of certain phyla and classes appears to result, at least in part, from the anatomical solutions to the evolution of macroscopic size that were arrived at largely during Ediacaran and Cambrian time. Larger-bodied animals, enabled by increased anatomical complexity, were increasingly able to mix the marine sediment and water columns, thus promoting stability in biogeochemical cycles. In addition, body plans that also facilitated ecological differentiation have tended to be associated with lower rates of extinction. In this sense, Cambrian solutions to Cambrian problems have had a lasting impact on the trajectory of complex life and, in turn, fundamental properties of the Earth system.

The origin and rise of complex life: progress requires interdisciplinary integration and hypothesis testing

“…Furthermore, the evolution of larger, mobile animals mixing sediments [68] and water columns is argued to have stabilized biogeochemical cycles. Overall, Payne et al agree with and augment previous analyses [69] that 'the evolution of complex life has, on the whole, strengthened stabilizing feedbacks in the climate system' [67]. If so, this is a remarkable observation-consistent with Lovelock and Margulis' Gaia hypothesis [70]-that the evolution of life has been making the Earth system more stable and resilient over time.…”

“…Payne et al [67] consider the relation between the evolution of complex life and the apparent stabilization of the Earth system in the Phanerozoic. It is well known that background extinction rates decline through the Phanerozoic, but why?…”

Adaptation to a Viscous Snowball Earth Ocean as a Path to Complex Multicellularity

“…The origin of metazoans and other groups with complex multicellularity during the Neoproterozoic not only transformed ecology but also the Earth system (Payne et al 2020). The hypothesis presented here provides a mechanistic explanation for the concurrent origin of complex multicellularity in a number of independent lineages.…”

Decreasing Phanerozoic extinction intensity as a consequence of Earth surface oxygenation and metazoan ecophysiology

“…(7,10,11)). Changes in the distribution of lineage ages and geographic range sizes, area of continental shelf environments, intensity of species interactions, frequency of geological triggers, stabilization of Earth's climate, and rock-area sampling biases have all been proposed as drivers of this trend (10)(11)(12)(13)(14). However, despite the long history of study and numerous proposed explanations, no consensus has been reached regarding the drivers of much higher early Paleozoic extinction rates vs. those of the later Paleozoic, Mesozoic and Cenozoic.…”