Shocking Discovery: Human Jaws Could be Traced Back to Ancient Armored Fish

A new study revealed that human jaw most likely evolved from extinct armored prehistoric fish that dominated the waters over 400 million years ago.

The study, published in the journal Science, was based on the discovery of a fossil fish in Yunnan, China. The newly discovered fossil, Qilinyu, has the classic placoderm skeleton but with the presence of the three key bones found in the jaws of modern humans.

The placoderms were extinct group of fishes that had similar jaw parts to humans consisting of dentary, maxilla and premaxilla. However, the jaws of placoderms, known as "gnathal plates," looked like sheet metal cutter or bony blades that slice together.

Due to the peculiarity of the placoderm's jaws, researchers have regarded the gnathal plates to be unrelated to human jaws. Additionally, the jaw bones of placoderms were located slightly further inside their mouth, which led the researchers to believe that the jaws of placoderms have evolved independently and were very distantly related to human jaws. 

Now, Qilinyu might change the previous notion regarding the origins of human jaws. Qilinyu, together with the Silurian fossil fish Entelognathus discovered in 2013, provided strong evidence that human jaws can be traced back to placoderms.

While both fish fossils share the same placoderm-like appearance and three-part jaw of bony fish, the researchers argued that Entelognathus and Qilinyu look quite different and have 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 and placoderm gnathal plates," explained Zhu Min of the Chinese Academy of Sciences, in a report from Xinhua News.

"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."

The researchers noted that the simplest explanation of their findings is that the human jaws have evolved from old gnathal plates of placoderms.