Brawn before brains in placental mammals after the end-Cretaceous extinction

Ornella C. Bertrand; Sarah L. Shelley; Thomas E. Williamson; John R. Wible; Stephen G.B. Chester; John J. Flynn; Luke T. Holbrook; Tyler R. Lyson; Jin Meng; Ian M. Miller; Hans P. Püschel; Thierry Smith; Michelle Spaulding; Z. Jack Tseng; Stephen L. Brusatte

doi:10.1126/science.abl5584

Brawn before brains in placental mammals after the end-Cretaceous extinction

Ornella C. Bertrand, Sarah L. Shelley, Thomas E. Williamson, John R. Wible, Stephen G.B. Chester, John J. Flynn, Luke T. Holbrook, Tyler R. Lyson, Jin Meng, Ian M. Miller, Hans P. Püschel, Thierry Smith, Michelle Spaulding, Z. Jack Tseng, Stephen L. Brusatte

Biological Sciences

Rowan University

Research output: Contribution to journal › Article › peer-review

Abstract

Mammals are the most encephalized vertebrates, with the largest brains relative to body size. Placental mammals have particularly enlarged brains, with expanded neocortices for sensory integration, the origins of which are unclear. We used computed tomography scans of newly discovered Paleocene fossils to show that contrary to the convention that mammal brains have steadily enlarged over time, early placentals initially decreased their relative brain sizes because body mass increased at a faster rate. Later in the Eocene, multiple crown lineages independently acquired highly encephalized brains through marked growth in sensory regions. We argue that the placental radiation initially emphasized increases in body size as extinction survivors filled vacant niches. Brains eventually became larger as ecosystems saturated and competition intensified.

Original language	American English
Pages (from-to)	80-85
Number of pages	6
Journal	Science
Volume	376
Issue number	6588
DOIs	https://doi.org/10.1126/science.abl5584
State	Published - Apr 1 2022

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Bertrand, O. C., Shelley, S. L., Williamson, T. E., Wible, J. R., Chester, S. G. B., Flynn, J. J., Holbrook, L. T., Lyson, T. R., Meng, J., Miller, I. M., Püschel, H. P., Smith, T., Spaulding, M., Tseng, Z. J., & Brusatte, S. L. (2022). Brawn before brains in placental mammals after the end-Cretaceous extinction. Science, 376(6588), 80-85. https://doi.org/10.1126/science.abl5584

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abstract = "Mammals are the most encephalized vertebrates, with the largest brains relative to body size. Placental mammals have particularly enlarged brains, with expanded neocortices for sensory integration, the origins of which are unclear. We used computed tomography scans of newly discovered Paleocene fossils to show that contrary to the convention that mammal brains have steadily enlarged over time, early placentals initially decreased their relative brain sizes because body mass increased at a faster rate. Later in the Eocene, multiple crown lineages independently acquired highly encephalized brains through marked growth in sensory regions. We argue that the placental radiation initially emphasized increases in body size as extinction survivors filled vacant niches. Brains eventually became larger as ecosystems saturated and competition intensified.",

author = "Bertrand, {Ornella C.} and Shelley, {Sarah L.} and Williamson, {Thomas E.} and Wible, {John R.} and Chester, {Stephen G.B.} and Flynn, {John J.} and Holbrook, {Luke T.} and Lyson, {Tyler R.} and Jin Meng and Miller, {Ian M.} and P{\"u}schel, {Hans P.} and Thierry Smith and Michelle Spaulding and Tseng, {Z. Jack} and Brusatte, {Stephen L.}",

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doi = "10.1126/science.abl5584",

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AU - Bertrand, Ornella C.

AU - Shelley, Sarah L.

AU - Williamson, Thomas E.

AU - Wible, John R.

AU - Chester, Stephen G.B.

AU - Flynn, John J.

AU - Holbrook, Luke T.

AU - Lyson, Tyler R.

AU - Meng, Jin

AU - Miller, Ian M.

AU - Püschel, Hans P.

AU - Smith, Thierry

AU - Spaulding, Michelle

AU - Tseng, Z. Jack

AU - Brusatte, Stephen L.

PY - 2022/4/1

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AB - Mammals are the most encephalized vertebrates, with the largest brains relative to body size. Placental mammals have particularly enlarged brains, with expanded neocortices for sensory integration, the origins of which are unclear. We used computed tomography scans of newly discovered Paleocene fossils to show that contrary to the convention that mammal brains have steadily enlarged over time, early placentals initially decreased their relative brain sizes because body mass increased at a faster rate. Later in the Eocene, multiple crown lineages independently acquired highly encephalized brains through marked growth in sensory regions. We argue that the placental radiation initially emphasized increases in body size as extinction survivors filled vacant niches. Brains eventually became larger as ecosystems saturated and competition intensified.

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Brawn before brains in placental mammals after the end-Cretaceous extinction

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