What turns an environmental disturbance into a mass extinction? A study in Physical Review Letters by Daniel Rothman of MIT and Sergei Petrovskii of the University of Leicester formalises an old intuition: catastrophe strikes when the pace of change exceeds the pace at which life can adapt. Their mathematical model observes that successful adaptation requires several conditions to hold simultaneously, so the probabilities multiply, yielding a bell-shaped distribution in which most animal groups adapt at intermediate rates.
To test the theory against deep time, the researchers compared its predictions with carbon-cycle records from 27 episodes spanning the past 450 million years, set alongside extinction-severity data compiled by palaeobiologist John Alroy. The model predicted the severity of most mass extinctions in Earth's history, lending quantitative support to the rate-mismatch hypothesis at a global scale. The end-Permian event, which eliminated more than 80 percent of marine species, aligns with ocean acidification that outstripped the capacity of organisms to adjust.
The framework's contemporary relevance is uncomfortable: the present rise in ocean carbon dioxide is approaching rates comparable to those that preceded past mass extinctions. By tying extinction risk to a measurable mismatch between environmental forcing and adaptive capacity, the work offers palaeontologists and climate scientists a common quantitative language for assessing how close modern ecosystems may be to similar thresholds.