Our jawed ancestors made their cousins extinct

Jawed ancestors
© iStock/A V S Turner

New fossil records demonstrate how our aquatic ancestors rose to dominance by becoming predators of their jawless cousins.

Palaeontologist at the University of Manchester have recently uncovered that changing pattern in the bite marks on fossil from early vertebrates. By studying fossils from varying periods, researchers were able to unlock the circumstances of human evolution.

Most modern vertebrates have jaws, such as mammals, birds and sharks, but 400m years ago jawless fish were more diverse. Palaeontologist previously hypothesised that the change from jawless to jawed could be because of changing environments, climates or competition. Research published in Proceedings of the Royal Society B, suggests another reason for the rise of the jawed vertebrate predator.

Researchers at the University of Manchester studied fossilised jawless fish and found that the frequency of bite marks increased through time, reaching a peak towards their extinction.

The bite marks included scratches, gouges and punctures in the skeleton of heterostracans, a now extinct jawless fish. Studying these bite pattern found an association with the occurrence of jawed vertebrates; as such our jawed relatives are believed to have played a role in the demise of our jawless relatives.

“It is really exciting to be able to find direct evidence of an ecological interaction between fossil organisms from millions of years ago, especially one that helps us construct our own distant evolutionary history.” said Dr Robert Sansom.

Dr Emma Randle, currently a Scientific Associate at The University of Birmingham said: “Hetersotracan jawless fishes are really interesting as they are some of the first vertebrates to have bone – in the form of an armour-like ‘exoskeleton’.

“They thrived for many millions of years and came in a variety of beautiful forms often dominating the environments they were found within.

“Ultimately, like other varieties of armoured jawless vertebrates, they became extinct towards the end of the Devonian Period, but leave us a fossil record that helps us reconstruct the early evolutionary history of all vertebrates”


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