Synapsid encephalization evolutionary stasis during end-Permian extinction (free pdf)
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Ben Creisler
May 17, 2026, 1:12:11 PM (2 days ago) May 17
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Ben Creisler
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Julien Benoit, Lucas J. Legendre, Ricardo Araújo, Vincent Fernandez, Adam Midzuk, Claire Browning, Fernando Abdala, Jennifer Botha & Kenneth D. Angielczyk (2026)
Evolutionary stasis in synapsid encephalization during the end-Permian mass extinction
Scientific Reports (advance online publication)
doi: https://doi.org/10.1038/s41598-026-53133-y
https://www.nature.com/articles/s41598-026-53133-y
Brain size and encephalization are correlated with extinction risks, making them central to understanding evolutionary outcomes in the face of the climatic and ecological challenges posed by mass extinction events. Yet, the end-Permian mass extinction—the most significant extinction event in the history of Life—has received little attention from a paleoneurological perspective. Here we use Synchrotron Radiation and CT scanning to study the evolution of brain endocasts of mammalian forerunners, the Permo-Triassic Synapsida, across this extinction event. During mass extinction events, it is expected that the brain would adapt either by growing larger to enhance behavioral response to the challenges, or shrinking to save energy. To test these predictions, we conducted a broad phylogenetic survey of synapsids across the end of the Permian and, unexpectedly, found stasis of the encephalization quotient. Furthermore, analysis of evolutionary rates indicates that stabilizing selection does not account for the observed stasis. We hypothesize that a lack of resources may have impeded neuroplasticity and prolonged a period of stasis that began in the late Permian. Brain size resumed varying after the crisis, marking the first steps toward the evolution of the mammalian brain.
Julien Benoit, Lucas J. Legendre, Ricardo Araújo, Vincent Fernandez, Adam Midzuk, Claire Browning, Fernando Abdala, Jennifer Botha & Kenneth D. Angielczyk (2026)
Evolutionary stasis in synapsid encephalization during the end-Permian mass extinction
Scientific Reports (advance online publication)
doi: https://doi.org/10.1038/s41598-026-53133-y
https://www.nature.com/articles/s41598-026-53133-y
Brain size and encephalization are correlated with extinction risks, making them central to understanding evolutionary outcomes in the face of the climatic and ecological challenges posed by mass extinction events. Yet, the end-Permian mass extinction—the most significant extinction event in the history of Life—has received little attention from a paleoneurological perspective. Here we use Synchrotron Radiation and CT scanning to study the evolution of brain endocasts of mammalian forerunners, the Permo-Triassic Synapsida, across this extinction event. During mass extinction events, it is expected that the brain would adapt either by growing larger to enhance behavioral response to the challenges, or shrinking to save energy. To test these predictions, we conducted a broad phylogenetic survey of synapsids across the end of the Permian and, unexpectedly, found stasis of the encephalization quotient. Furthermore, analysis of evolutionary rates indicates that stabilizing selection does not account for the observed stasis. We hypothesize that a lack of resources may have impeded neuroplasticity and prolonged a period of stasis that began in the late Permian. Brain size resumed varying after the crisis, marking the first steps toward the evolution of the mammalian brain.
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