A group of scientists revealed Wednesday they have found evidence that the enamel on our teeth originally came from scales on a prehistoric fish that live some 400 million years ago.

Paleontologist Per Erik Ahlberg of Sweden’s University of Uppsala said in an article on csmonitor.com, “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.”

Most vertebrates have tooth enamel, which is made up almost entirely of calcium phosphate, and is the hardest tissue produced by the body.  Scientists have been unclear as to the origin of the substance.

The researchers, looking at fossil remains of two bony fish from the Silurian Period, discovered the fossils had enamel coating on their scales, but not on their teeth.  It took millions of years for the fish to begin to develop enamel on their teeth to make them stronger and harder.

One of the fish fossils was called Andreolepis and lived in the area we now know as Sweden about 425 million years ago.  The other, Psarolepis, existed in what is now China about 418 million years ago.  Both fossils exhibited an enamel coating on their scales, and neither had tooth enamel.

Believe it or not, a modern fish is also providing clues.  The spotted gar, a freshwater fish usually found in central and southern United States, has scales that are covered by an enamel-like substance.  Since the gar has remained relatively unchanged since the time of the dinosaurs, the scientists looked genes relating to enamel formation in the fish, and found that the scale covering is similar to enamel.

Paleontologist Qingming Qu of Uppsala University and the University of Ottawa added the original use of enamel was as a protective tissue in primitive fishes.

The research appears in the journal Nature.