Two fossil fish have provided clues as to the evolution of enamel. It probably began as a residue of the skin instead of the teeth.
A question that has always haunted scientists and researchers is the evolution of enamel. Where did the outer covering of teeth originally come from? Paleontologists and genetic engineers have got together to solve this puzzle. And it looks like they just might have solved it. The answer is that it evolved in the skin and entered the teeth only much later.
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The glowing and bright enamel is the crowning creation of teeth in human beings. Every time we polish those choppers with a toothbrush and toothpaste, we get a glimpse of our enamel.
It happens to be the most toughest of surfaces produced by the human body. The mineral apatite (calcium phosphate) is spread onto a matrix of proteins and that is how we get enamel.
While we have teeth only in the mouth, several species of fish have tooth-like structures on the surface of their skins. Sharks happen to be one such species. Two fossil fish, Psarolepis from China and Andreolepis from Sweden, provide clues as to the evolution of enamel.
Both fish are over 400 million years old. And they had enamel in their scales. It is called ganoine and it served a very crucial role for both types of fish.
"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," explains Per Ahlberg, Professor of Evolutionary Organismal Biology at Uppsala University.
While the ancient fish did have enamel in their scales, they did not have any enamel on their teeth. This might appear odd at first but it is a fact. Since marine life forms were evolving rapidly at this time, the changes were taking place in their structures. Yet it took millions of years for these fish to develop an enamel coating on their teeth.
It comes as somewhat of a surprise. The lack of enamel in the teeth of the earliest bony fish shows that they were prototypical and primitive. Thus enamel evolved via the skin as an outer membrane.
Previously it was believed that enamel evolved in the mouth from hardened scales. But now it appears to be the case that it started its journey as a part and parcel of the skin. Only later on did it make the critical shift from skin to mouth.
The stuff that makes our teeth so hard and resistant to breakdown was on the skin of garfish and other bony fish in the distant past. It served its function as a safety measure against predators.
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The study published in the journal Nature.