Scientists in China have stumbled across an ancient fish that could totally change how we understand our own evolution. Researchers believe that our jaw is the end result of an evolutionary journey that began 423 million years ago with a fish that has long since gone extinct.

The special feature of our jaw that allows it to chew is something that scientists had believed evolved separately from other animals. But now it appears that an extinct fish known as a placoderm was the first to have this ability, according to a statement from Uppsala University.

Researchers at the Chinese Academy of Sciences in Beijing compared the jaw from this ancient fish discovered three years ago to a more recent fossil in the same place, and found that the Entelognathus fossil was the most primitive vertebrate to have a jaw that resembles that of modern humans.

“Where did our jaws come from?,” the statement reads. “The question is more complicated than it seems, because not all jaws are the same. In a new article, published in Science, palaeontologists from China and Sweden trace our jaws back to the extinct placoderms, armoured prehistoric fish that lived over 400 million years ago.

“Jaws are an iconic and defining feature, not only of our own anatomy but of all jawed vertebrates: not for nothing did Steven Spielberg use ‘Jaws’ as the one-word title of his immortal shark epic,” it continues. “Jaws first appear in the developing embryo as a cartilage bar similar to a gill arch. In a shark, this develops directly into the adult jaws, but in an embryo of a bony fish or a human being new bones appear on the outside of the cartilage. In our own skull, these bones – the dentary, maxilla and premaxilla – make up the entire jaws and carry our teeth.”