The scales of a 420-million-year-old fish may be the reason why we now have enamel on our teeth, a new study suggest.
By analysing the DNA collected from various species of animals, as well some ancient fish fossils, scientist managed to figure out where the enamel first originated.
Mammals, reptiles, birds, and amphibians all have enamel in their bodies. Fish from the Sarcopterygii class, one of them being the lobe-finned fish, also have enamel.
According to the researchers there were some species of primitive fish that had enamel covering their bodies, as well as their teeth.
After examining the skeleton and teeth of different types of fish, the conclusions were that the enamel originated in fish who had their skeleton made of calcified bone, and not made out of cartilage such as the skeleton of rays and sharks.
For their study, the researchers also examined two types of ancient fish that both lived in the southern area of present-day China about 418 to 420 million years ago. The first fish that they examined was called Psarolepis, a 418 million-year-old ancient lobe-fish, but the researchers found that the enamel was absent from the fish’s teeth.
The second fish that they examined was the Anreoleps, an extinct genus of the order Actinopterygii from the family Andreolepididae, that lived about 420 million years ago around the same time as the Psarolepis. Researchers found that the Anreoleps fish did not have enamel in its skeleton and skull, but it had enamel on its scales. The results showed that this was the only species of fish to have enamel on its scales but nowhere else in its body.
“Enamel originated on the scales, before colonizing the dermal bones and finally the teeth,” wrote the authors in their study report that was published Wednesday in the journal Nature.
Tooth enamel is a major tissue that is found in human teeth, as well as many other animals. It is the hardest substance in our bodies, containing 96 percent minerals. It acts as a shield that protects our teeth from painful temperatures (too cold or too hot), and it also protects them when we chew, crunch, bite, etc.
Image Source: ckdental