An astounding discovery related to an ancient fish could change the way scientists view human evolution, and specifically where we got our unique jaw. Chinese scientists determined that our jaw didn’t develop separately, but was rather the end result of an evolutionary process that began with an ancient, extinct fish from 423 million years ago.

Our jaws have a special feature that allows us to chew, and scientists though this evolved separately from other animals, but it appears that the placoderm, an extinct fish from eons ago, may have started this evolutionary journey that has culminated in our own jaws, according to a statement from Uppsala University.

The researchers determined that the Entelognathus fossil was the most promitive vertebrate to have a jaw that resembled that of modern humans. This fossil was discovered three years ago and was compared to a newer fossil, which allowed researchers to come to their findings.

“This is where the new fossil, Qilinyu, comes in,” the statement reads. “Qilinyu, described this week in Science by palaeontologists from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) in Beijing and Uppsala University in Sweden, comes from the same place and time period as Entelognathus, and also combines a placoderm skeleton with dentary, maxilla and premaxilla, though the two fishes otherwise look quite different and must have had different lifestyles.

“Looking at the jaw bones of Entelognathus and Qilinyu we can see that they, in both fishes, combine characters of the bony fish jaw bones (they contribute to the outer surface of the face and lower jaw) and placoderm gnathal plates (they have broad biting surfaces inside the mouth),” the statement adds. “Another thing becomes apparent as well: it has been argued that placoderm gnathal plates represent an inner jaw arcade, similar in position to the ‘coronoid bones’ of bony fishes, and if that were true we would expect to find gnathal plates just inside of the dentary, maxilla and premaxilla of Entelognathus and Qilinyu; but there is nothing there.”