Enamel, the ultra-tough coating protecting humans' teeth, evolved from the scales of ancient fish.
According to The Los Angeles Times, authors of a study published in the journal Nature made this conclusion by studying the DNA of living creatures, as well as fossils of fish that had scales with a makeup similar to tooth enamel. The scientists found a link in the tissue of the fish's scales and enamel.
The researchers examined the fossils of two ancient fish: one from China, Psarolepis, and one from Sweden, Andreolepis. Both hundreds of millions of year old, the ancient fish had enamel in their scales, though the former also had it in its teeth.
"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," study co-author Per Ahlberg, professor of evolutionary organismal biology at Uppsala University, said in a press release.
Enamel is the toughest tissue in the human body and it also appears in most mammals, birds, amphibians, and reptiles. But because Andreolepis did not have enamel in its skull, the researchers determined it was a different kind of fish from Psarolepis.
The researchers concluded in their study, according to The Times, "enamel originated on the scales, before colonizing the dermal bones and finally the teeth."
