Tooth enamel evolved from fish scales.

Enamel is the hardest tissue produced in the bodies of people and other vertebrates, including fish. But until now, scientists were unclear about whether enamel originated in teeth or evolved from a tissue resembling enamel called ganoine. Researchers at Uppsala University in Sweden noted that certain fish such as sharks have enamel on their teeth and dermal denticles, or little tooth-like scales, on the outer surfaces of their bodies.When they examined prehistoric fish fossils they found an enamel coating on their scales, but no enamel on their teeth. Only millions of years later through evolutionary processes did fish exploit the enamel to make teeth harder and stronger. “This is important because it is unexpected. In us, enamel is only found on teeth, and it is very important for their function, so it is natural to assume that it evolved there,” said palaeontologist Professor Per Erik Ahlberg of Sweden’s University of Uppsala.