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Proceedings of the International Academy of Ecology and Environmental Sciences, 2026, 16(3): 89-122
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Article

What triggers explosive radiations and mass extinctions? A unified critical transition framework

WenJun Zhang
School of Life Sciences, Sun Yat-sen University, Guangzhou, China

Received 3 April 2026;Accepted 21 April 2026;Published online 30 May 2026;Published 1 September 2026
IAEES

Abstract
Abstract The two most dramatic phenomena in the history of life, explosive evolutionary radiations and catastrophic mass extinctions, have traditionally been studied as separate problems with distinct causal mechanisms. This paper challenges that divide by proposing that both are manifestations of a single underlying process: the crossing of critical thresholds in a complex adaptive system. I conceptualize the global ecosystem as a high-dimensional ecological landscape whose topography is jointly shaped by three macroscopic order parameters, system resilience R, environmental pressure S, and evolutionary potential I. Through a unified mathematical framework combining stochastic differential equations, network percolation theory, and the physics of critical transitions, I show that mass extinctions correspond to collapse transitions occurring when environmental stress overwhelms a system whose resilience has been eroded, while evolutionary radiations correspond to innovation transitions occurring when accumulated evolutionary potential breaches a nucleation threshold under permissive conditions. The model predicts that both types of transition are preceded by detectable early-warning signals, critical slowing down, increasing variance, and rising autocorrelation, that arise from the same dynamical origin. Network percolation provides the mechanistic link: the fragmentation of the ecological interaction network below a critical connectivity defines the collapse cascade, whereas the re-establishment of a percolating network of novel interactions defines the radiation cascade. The theory resolves long-standing puzzles, including the synchronicity of the Cambrian explosion, the variable magnitude of mass extinctions under similar external forcings, and the frequently delayed recoveries following extinction events. Applied to the contemporary biodiversity crisis, the framework yields a sobering quantitative prediction: the simultaneous erosion of functional redundancy and modularity (decreasing R) coupled with accelerating climatic and chemical perturbations (increasing S) is driving the modern biosphere toward a collapse threshold, and early-warning indicators are already detectable in multiple ecological time series. The unified criticality model thus offers both a retrospective understanding of life's grandest ebbs and flows and a prospective tool for anticipating the next potential mass extinction.

Keywords macroevolutionary dynamics;critical transitions;mass extinction;evolutionary radiation;ecological resilience;network percolation;early-warning signals;complex adaptive systems.


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