How mammals survived the dinosaurs by chewing differently

By Dominic Kleinknecht
Eberhard-Karls-University Tübingen

A new study at the University of Chicago found that mammal jaws evolved to also allow for side-to-side motions of the jaw. As a result, food could not only be bitten but also be grinded with the molar teeth, which meant that mammals could have a more diversified diet. The study goes even further and states that the resulting dietary advantage helped mammals survive and thrive after the mass extinction at the end of the Cretaceous Period 66 million years ago that saw the demise of the dinosaurs.

David Grossnickel, UChicago grad student and author of the study, looked into functional advantages that mammals might have had over dinosaurs in order to explain why we are finding ourselves in the age of mammals instead of still being in the age of dinosaurs.  Therefore, he analyzed the structure of teeth, jaw bones, and the attachment sites of controlling muscles using 2D images of early mammal fossil and collected 3D data of modern specimens. What he found was that while the molar teeth developed to better fit into the corresponding counter-molar of the opposing jaw, the musculature simultaneously evolved to allow for side-by-side or grinding motions. This meant that both a pitch rotation resulting in up-and-down movements for biting as well as a yaw movement for grinding food like a pestle and mortar was possible. This duality of movements is a shared feature of almost all modern mammals and meant that early mammals could eat a broader range of available foods, and be more resourceful during tough times of food scarcity. According to Grossnickel, this adaptations and dietary advantages might have been crucial to the early mammals’ survival and a key characteristic that played into heralding the start of the mammalian era.


University of Chicago Medical Center. "How chewing like a cow helped early mammals thrive: Study shows how mammal jaws evolved to help our earliest ancestors eat a more diversified diet." ScienceDaily. ScienceDaily, 23 March 2017. <>.