Incredible Shark Fossil Hints At Split from Human Ancestors 440 Million Years Ago

Sharks and humans have a common ancestor dating back 440 million years ago, according to a study published Tuesday. The new investigation of an ancient shark fossil further unravels the evolutionary history of sharks, and helps us understand our very distant and ancient origins.

The study, in the Proceedings of the Royal Society B, investigated an ancient shark species called Gladbachus adentatus that was first studied in 2001, after its discovery in the late 1990s. Only one specimen of this species has been found and cutting-edge imaging technology allowed researchers to study it in extremely close detail, according to Michael Coates, the lead author and professor at University of Chicago’s organismal biology and anatomy department.

This species, according to Coates, isn’t the common ancestor of sharks and humans, but hints at what that ancestor may have looked like. Gladbachus, though relatively young, has features seen in even older fossils, such as its tiny scales. "The scales themselves are like tiny teeth," Coates told Newsweek.

GettyImages-102639763 Visitors watch sharks and other fish swimming in an aquarium tunnel on July 6, 2010 at the Sea Life aquarium in Oberhausen, western Germany. Getty

The up-close data of this shark's scales points to a "tell-tale sign" that sharks could be older than previously thought. Isolated scales that date older than this fossil could be tied to a shark or at least a shark-like species. If isolated scales of other specimens are that of sharks, it means that sharks could be traced back 440 million years, as estimated in the study. If sharks are that old, human ancestors can be traced back at least that far too.

As all species are ultimately on the same massive family tree, an ancient species once existed that is on the lineage of both humans and sharks. That species—though we don't know which—would have been the last commonality between humans and sharks before the 'branch' of the family tree split. The Gladbachus fossil pushes scientists' knowledge of when that branch split—further back into time. 

Other features of the 2.6-foot-long shark fossil included a wide mouth, splayed-out gills and various kinds of teeth, reported Live Science. Shark fossils such as this one are incredibly rare, according to Coates. Gladbachus is among the oldest shark fossils, branching off from near the base of the shark family tree. That offers a "unique perspective" on the details of what is happening at the base of the shark tree, which is barely understood or sampled, he said.

F1 Gladbachus adentatus, an ancient shark species discovered in the late 1990s and re-investigated with cutting edge technology in a study published in Proceedings of the Royal Society B on January 2, 2018. Proceedings of the Royal Society B

This specimen also includes many parts of the body, not just isolated pieces. The study showed that sharks were early specialists, not the primitive species that they are often described as. "We can see the full repertoire of different kinds of scales."

This species, he said, is “lifting the lid on just a glimpse of this early diversity.” That's what is exciting about the findings, Coates said. It offers a "clue about how diverse these sharks were." 

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