415 Million-Year-Old Fish Fossil Suggests That Humans Don't Share a Common Ancestor With Sharks, Claim Researchers

In 2015, researchers claimed that the last common ancestor shared by all jawed vertebrates wasn't completely shark-like. This assertion was made after analyzing a 415 million-year-old fish skull from Siberia, the University of Oxford stated. Another observation experts made with the fossil was that sharks were not 'primitive' and could have had advanced features. 

The fish was labeled Janusiscus after the double-faced Roman god Janus. Researchers chose this name because of the 'two-face' nature of the creature. In 1972 when it was first discovered, the external features implied that it had a skeletal structure similar to an early bony fish (or osteichthyan). Later when the researchers examined the fossil through X-ray and CT Scans, it was unveiled that its braincase was akin to that of cartilaginous fishes (or chondrichthyans) which also includes sharks. This duality caused the creature to get its name. 

The age and features of the fossil placed the creature as the ancestor of all jawed vertebrates. Before this finding chondrichthyans were believed to be the primitive ancestor of jawed vertebrates, because of the absence of bony skeletons. This fossil though challenges this assertion, as it showcases that there was a primitive ancestor of jawed vertebrates that had both shark-like and bony-fish-like properties.

"The results from our analysis help to turn this view on its head: the earliest jawed vertebrates would have looked somewhat more like bony fishes, at least externally, with large dermal plates covering their skulls," explained Sam Giles of Oxford University’s Department of Earth Sciences. "In fact, they would have had a mix of what are now viewed as cartilaginous- and bony fish-like features, supporting the idea that both groups became independently specialized later in their separate evolutionary histories."

The finding gives experts different perspectives regarding the evolution of vertebrates. "This 415 million-year-old fossil gives us an intriguing glimpse of the 'Age of Fishes' when modern groups of vertebrates were really beginning to take off in an evolutionary sense," said Dr. Matt Friedman of Oxford University’s Department of Earth Sciences. "It tells us that the ancestral jawed vertebrate probably doesn’t fit into our existing categories." This discovery also indicates that shark's features evolved throughout several millenniums. At one point, the shark-like and bony-fish-like attributes separated in evolution, researchers suggested. This indicates that shark's forefathers were as bony as humans.  

Experts claim that Janusiscus has given credence to the assertion that Sharks came later in the vertebrate family, and have advanced features that were adapted to cope with the surroundings. "It's misleading to think of evolution as a ladder which we reconstruct with 'missing links',"  Martin Brazeau of Imperial College London said, stated IFL Science. "It's more accurate to think of it as a family tree, and research into evolution is like solving a puzzle. Each new piece you find throws the surrounding pieces into context and helps you to understand them better. Janusiscus has helped us to look at sharks differently and will ensure they are no longer dismissed as being 'frozen' at a primitive stage of evolution."