Enamel is responsible for giving out teeth some bite, and now scientists may have worked out where it originates from.
A team of researchers have revealed that new fossil and genetic evidence suggests that enamel in fact evolved from the scales of ancient fish which swam the seas around 400 million years ago. Scientists have long puzzled where enamel came from before becoming part of our teeth.
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Tooth enamel comes from fish scales, say researchers
In the body of humans and other vertebrates, enamel is the hardest tissue. Now scientists may be able to explain where it comes from, using the fossils of two primitive fish.
After examining the bony fish from the Silurian Period, they found enamel coating on their scales but not on their teeth. The team noted that only millions of years later did enamel coating start to appear on the fish teeth.
“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 paleontologist Per Erik Ahlberg of Sweden’s University of Uppsala.
Enamel itself is made up almost entirely of calcium phosphate, and is one of the main tissues in the teeth of the majority of vertebrates. Terrestrial vertebrates such as amphibians, reptiles, birds and mammals, including humans, are all descended from fish.
Fossil and genetic research provide evidence
“Although this tissue on our teeth is used for biting or shearing, it was originally used as a protective tissue such as in living primitive fishes including gars and bichirs,” added paleontologist Qingming Qu of Uppsala University and the University of Ottawa.
The researchers studied the fossil of a fish called Andreolepis, which lived 425 million years ago in Sweden, and found it had a thin layer of enamel on its scales. Psarolepis, a fish which lived 418 million years ago in China, had enamel on its scales and its face. Neither fish had enamel on its teeth.
Genetic research of a freshwater fish known as the spotted gar provided further evidence. The spotted gar has hardly changed since the age of the dinosaurs, but its scales are covered in an enamel-like substance.
Researchers were able to isolate genes related to enamel formation, proving that the substance is a kind of enamel.