Our teeth may have evolved from the jagged scales of ancient fish, the remnants of which can be seen embedded in the skin of sharks and skates, a study has found.
Recent studies on species such as zebrafish showed scales and teeth developing from distinctly different clusters of cells in fish embryos, pouring cold water on teeth from scales theories.
However, while most fish in the sea have bones, one ancient lineage - sharks, skates, and rays - possess skeletons made entirely of cartilage.
Researchers at the University of Cambridge in the UK used fluorescent markers to track cell development in the embryo of a cartilaginous fish - a little skate in this case - and found that these thorny scales are in fact created from the same type of cells as teeth: neural crest cells.
"Stroke a shark and you will find it feels rougher than other fish, as shark skin is covered entirely in dermal denticles," said Andrew Gillis, from the University of Cambridge.
"Theres evidence that shark skin was actually used as sandpaper as early as the Bronze Age," said Gillis.
The findings, published in the journal PNAS, support the theory that, in the depths of early evolution, these denticle scales were carried into the emerging mouths of jawed vertebrates to form teeth.
"Neural crest cells are central to the process of tooth development in mammals," said Gillis.
"Our findings suggest a deep evolutionary relationship between these primitive fish scales and the teeth of vertebrates," he said.