For sea otters, a trip to the dentist is no sweat. The protective enamel on their teeth is more than twice as strong as humans' enamel — but it wasn’t always this way. Long ago, scientists say in a new study, early humans’ teeth were just as strong as sea otters’ clam-crunching pearly whites. And this finding could be a key to understanding our earliest ancestors’ dietary habits.

Chipping Teeth

Tooth enamel in most animals is comprised of tiny prism-like crystals clumped together to form criss-crossing protective sheets. The manner in which the crystalline sheets are layered can affect toughness, and this pattern is what varies most among mammals' teeth structures. Sea otters are known for chomping down on hard-shelled creatures like mussels and clams. To see just where this tooth strength came from, researchers tested the canines and molars from preserved sea otter skulls, using a machine that measured the force needed to chip the enamel. They found that sea otter teeth were 2.5 times more resilient to chipping than modern humans’ teeth. The circular arrangement of sea otters’ enamel layers, which varies from modern humans, could play a role in resisting cracking. Researchers published their findings Tuesday in the journal Biology Letters

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Equal Biting Power

Similar tooth strength tests have previously been performed on fossil remains of early human ancestors, and the data show they also had much stronger teeth than modern people. In fact the early hominin Paranthropus boisei had teeth just as strong as the sea otters. This indicates that early humans’ diets may have been awfully crunchy, and that our enamel has weakened over time. Currently, there’s scant evidence on the role enamel microstructure patterns play in tooth strength among other species. However, researchers believe enamel variations could be a key area of future research to understand the evolution and dietary habits of our earliest ancestors and other extant animals. As to whether they played with their food while floating on their backs, however... well that might be where the similarities end.

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