Enamel 'Fished' Its Way Into Your Mouth, Study Claims

What's common in humans and ancient bony fish that swam the oceans 400-million years ago? Enamel.

That's right. The white substance that humans work a shine on every morning did not evolve in the mouth. New research suggests it evolved on the scales of fish and later colonized teeth. The study examined fossils and a living archaic bony fish to find that the latter has genes that code for two enamel proteins that are also found in humans.

Paleontologists and genomic experts at Uppsala University in Sweden and the Institute of Vertebrate Palaeontology and Palaeoanthropology (IVPP) in China studied the fossils of 400-million-year old Psarolepis and Andreolepis. They also sequence the genome of the gar fish, an archaic fish from North America. In gar, the gene is expressed in the skin resulting in ganoine, a form of enamel. In humans enamel is the hardest susbtance the body produces, composes entirely of calcium phosphate.

Besides finding genes expressed for enamel proteins in both humans and gar fish, researchers established that Psarolepis and Andreolepis had enamel on their scales but no enamel in mouths. Psarolepis also had enamel on denticles covering its faces. Some also have enamel on denticles.

"Psarolepis and Andreolepis are among the earliest bony fishes, so we believe that their lack of tooth enamel is primitive and not a specialization. It seems that enamel originated in the skin, where we call it ganoine, and only colonized the teeth at a later point," Per Ahlberg, a professor of Evolutionary Organismal Biology at Uppsala University stated in a press release.