The origin of teeth in vertebrates, therefore including in humans, has been long wondered and debated. Scientists have questioned whether teeth descended as part of the origin of the jaw, or if they had their own unique formation. More clarification has just been released to this mysterious question of our anatomy, with new recent data leading scientists to believe that teeth in the animal kingdom evolved from the scales of ancient fish, due to the shared characteristic of neural crest cells. The scales are still present today, covering the bodies of fish such as sharks, skate and rays.
The specific linage of sea life possessing skeletons fully made of cartilage consists of sharks, rays and skates. These fish still have primitive characteristics, such as “dermal denticles”, which are embedded into their skin. Dermal denticles share an extremely similar appearance of jagged teeth, as they are small sharp scales.
Recently, research scientists at the University of Cambridge tracked the cell development in the embryo of a the cartilaginous skate fish, using have used fluorescent markers. Through this method, they uncovered the new linking piece of information: the thorny scales are created from “neural crest cells”, the same type of cells that make up vertebrate teeth! This information provides further support to the theory that evolution of jawed teeth found currently in the mouths 99% of sea and mammal vertebrates, evolved from the scales of these fish.
Though the scales found on fish currently appear very different from teeth, the scales of ancient fish were much more similar to the tooth like structure of today. The reason for this, in the words of Dr. Andrew Gillis from Cambridge’s Department of Zoology and the Marine Biological Laboratory in Woods Hole, is that the scales of most fish that live today, like the cartilaginous fishes of skate and shark, have only retained some lineages to the primitive scales. Researchers at Cambridge hypothesize that amour plates consisted of many different layers of foundation of bone, an outer layer of dentine and cells in unborn embryos. They propose that this composition underwent many reductions and modifications. Shark’s scales do however further support this theory, as the dermal denticles they are covered in, give them a much rougher feel, than other fish. It is very possible that this also is because the denticles found on these fishes are remnants of superficial amour plating, of the early ancient skeletons of vertebrates.
This article and data finding was very thought provoking to me. I was not aware that of the uncertainty of the origin of teeth, in the world of science. Also because I am extremely interested in evolution and the origination of our species, this finding specifically intrigued me, as this data may be useful for new advances in evolutionary theories. It is fascinating to me consider the possibility of such a key part of vertebrates, specifically of humans, being so closely linked to fish, as that is a species of animal than I have ever considered having ties to human descent before. I think this data is a gateway to future discoveries that will be beneficial to the science world.
(Be sure to check out the second secondary source article linked below, as it discusses even more data on specially teeth enamel evolving from fish scales!)