Brain size and neuron numbers drive differences in yawn duration across mammals and birds

Massen, Jorg J M; Hartlieb, Margarita; Martin, Jordan S; Leitgeb, Elisabeth B; Hockl, Jasmin; Kocourek, Martin; Olkowicz, Seweryn; Zhang, Yicheng; Osadnik, Christin; Verkleij, Jorrit W; Bugnyar, Thomas; Němec, Pavel; Gallup, Andrew C

doi:10.1038/s42003-021-02019-y

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Massen, J. J. M., Hartlieb, M., Martin, J. S., Leitgeb, E. B., Hockl, J., Kocourek, M., Olkowicz, S., Zhang, Y., Osadnik, C., Verkleij, J. W., Bugnyar, T., Němec, P., & Gallup, A. C. (2021). Brain size and neuron numbers drive differences in yawn duration across mammals and birds. Communications Biology, 4, 503. https://doi.org/10.1038/s42003-021-02019-y

Abstract

Recent studies indicate that yawning evolved as a brain cooling mechanism. Given that larger brains have greater thermolytic needs and brain temperature is determined in part by heat production from neuronal activity, it was hypothesized that animals with larger brains and more neurons would yawn longer to produce comparable cooling effects. To test this, we performed the largest study on yawning ever conducted, analyzing 1291 yawns from 101 species (55 mammals; 46 birds). Phylogenetically controlled analyses revealed robust positive