Scientists discover the evolutionary origins of our smile

Humans owe their pretty grins to a prehistoric fish which roamed the oceans over 400-million-years ago, a new study has found.

The gruesome gnashers of the primitive fish called Compagopiscis suggests humans may have developed working teeth and jaws much earlier than previously thought.

A 380 million-year-old fossil of the fish, found in Australia, was examined under the latest high energy X rays to create a 3-D image of what it would have looked like.

Researchers led by the University of Bristol, who studied the jaws of Compagopiscis, found that these earliest jawed vertebrates possessed teeth too.

This indicates our whites evolved along with, or soon after, the evolution of jaws, they said.

It takes both teeth and jaws to make a pretty smile, but the evolutionary origins of these parts of our anatomy have only just been discovered.

All living jawed vertebrates (animals with backbones, such as humans) have teeth, but it
has long been thought that the first jawed vertebrates lacked pearly gnashers, instead capturing prey with gruesome scissor-like jaw-bones.

Researchers studied fossils of Compagopiscis using high energy X-rays at the Swiss Light Source at the Paul Scherrer Institut in Switzerland, revealing the structure and development of teeth and bones.

"We were able to visualise every tissue, cell and growth line within the bony jaws, allowing us to study the development of the jaws and teeth. We could then make comparisons with the embryology of living vertebrates, thus demonstrating that placoderms possessed teeth," lead author, Dr Martin Ruecklin of the University of Bristol said.

"This is solid evidence for the presence of teeth in these first jawed vertebrates and solves the debate on the origin of teeth," co-author, Professor Philip Donoghue of the University of Bristol's School of Earth Sciences said.

"These wonderfully preserved fossils from Australia yield many secrets of our evolutionary ancestry but research has been held back waiting for the kind of non-destructive technology that we used in this study," said co-author Dr Zerina Johanson from the Natural History Museum.

The study findings have been published in the journal 'Nature'.