Ancient Fossil Reveals Human Ancestors Were Not 'Shark-Like' (VIDEO)

Scientists have learned a bit more about the the last common ancestor of all jawed invertebrates. By looking at a 415 million-year-old fish skull, they've discovered that this common ancestor was, most likely, not very shark-like and that sharks, in general, aren't "primitive."

"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 Matt Friedman, one of the researchers, in a news release. "It tells us that the ancestral jawed vertebrate probably doesn't fit into our existing categories."

The fossil skull has external features that seemed to suggest that it belonged to the bony fishes, osteichthyans. Yet when scientists used X-ray CT scanning to look inside the skull, they found that the structure surrounding the brain was more similar to cartilaginous fishes, chondrichthyans. These include sharks and rays.

Chondrichthyans have often been viewed as primitive, and treated as proxies for what the "ancestral" jawed vertebrate would have looked like. Yet this latest analysis seems to disprove this idea.

"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," said Sam Giles, first author of the new study. "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 findings show that, in this case, sharks and rays actually are more evolutionarily advanced than expected. Because this fossil skull displays features from both groups, it's clear that later specialization occurred.

The findings are published in the journal Nature.

Want to see the scanned fossil for yourself? Check out the video below, courtesy of YouTube.

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