Our tooth enamel was once our scaly skin

Researchers report enamel-like material on the skin of sharks, also suggesting that our tooth protection originated in our skin. Scientists from the fields of palaeontology and genomics have combined efforts to find an unexpected lead in the origins of the hardest material our body creates: tooth enamel. It would appear that the materials our body emits to create enamel originated in our skin and, as we evolved, moved to our teeth.

The enamel in our teeth is made almost entirely by mineral apatite (calcium phosphate). We have three enamel matrix proteins on which this calcium phosphate is deposited, and the result is lovely, hard, chewing and tearing-friendly teeth.

These materials – and similar materials – are not entirely unique to humans.

Researchers Per Ahlberg and Qingming Qu of Uppsala University have run a study with researcher Min Zhu from IVPP in Beijing on a couple of fossil fishes. These fish, Psarolepis from China and Andreolepis from Sweden, are both more than 400-million years old.

In Andreolepis, the scales were found to have enamel. In Psarolepis, both the scales and the denticles of the face were found to have enamel.

No enamel is found on the teeth on either creature.

"Psarolepis and Andreolepis are among the earliest bony fishes, so we believe that their lack of tooth enamel is primitive and not a specialization," said Per Ahlberg, Professor of Evolutionary Organismal Biology at Uppsala University.

"It seems that enamel originated in the skin, where we call it ganoine, and only colonized the teeth at a later point."

For more information, see the paper "New genomic and fossil data illuminate the origin of enamel" by authors Qingming Qu, Tatjana Haitina, Min Zhu, and Per Erik Ahlberg. This paper can be found in the scientific journal Nature under code doi:10.1038/nature15259.