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What Makes Sea Otter Teeth Especially Tough

Oct 20, 2014 06:17 PM EDT

Despite the fact that sea otters have teeth made out of the same material as human teeth, they are somehow able to crunch though tough clams, crabs, and other shelled creatures without fear of chipping a tooth. Now, researchers think they figured out the secret of these super-strong teeth.

A study recently published in the journal Biology Letters details how the dental enamel of otters appears to have a incredibly unique microstructure - a coating that makes otter teeth up to two-and-a-half times tougher than human teeth.

The study looked at the probable force it took for otter teeth samples to chip, suspecting that it takes significantly more intense blunt force to crack otter enamel than previously thought.

All mammals boast teeth coated in enamel - tiny crystals of calcium phosphate that give a tooth's surface its hardness. This enamel can be worn down by things like plaque and acid, but traditionally can stand the test of time unless subjugated to a heavy enough blunt force.

That's thanks to the fact that these enamel crystals are separated by thin layers of protein-rich gel that helps prevent cracks from propagating. Human enamel boasts about 14 layers of crack-stopping layers per millimeter of tissue. The new study found that sea otters boast five additional layers per millimeter, significantly booting the effectiveness of their enamel to resist blunt force.

Interestingly, the authors note that the unique circular pathing of enamel structure in otter teeth actually resembles that of structures seen in Paranthropus boisei - early Homo sapiens commonly called "nutcracker men" who lived in East Africa between 1.2 and 2.3 million years ago.

This might indicate that early humans once could bite through very tough substances, but were never presented with adequate environmental pressures to select for the trait permanently, especially after they moved to new regions and were presented with softer foods.

Still, that all remains pure speculation.

"Understanding more about extreme adaptations and variability in the enamel of extant animals will aid in deciphering dietary habits of our own lineage and close relatives," the authors concluded.

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