Human beings evolved from ancient shark-headed animals over 300 million years ago, new research claims.
A study published in the journal Science says that the pre-historic fish, Acanthodes bronni was the common ancestor of all jawed vertebrates including humans.
According to the research, around 400 million years ago, fish went through an evolutionary divorce that would someday be very relevant to humans. The split produced the two major groups of fish we see in our world today: those with skeletons of bone, which make up the majority of aquatic life, and those with cartilaginous skeletons, which today include the sharks, rays, and skates.
All of the animal life on land including human beings reportedly belongs to the bony fish family.
The Paleozoic era acanthodians are known primarily from fossilized scales and elaborate fin spines, have been classified variously as both sharks and bony fish since their discovery.
"Unexpectedly, Acanthodes turns out to be the best view we have of conditions in the last common ancestor of bony fishes and sharks," stated co-author Michael Coates, professor of organismal biology and anatomy at the University of Chicago. "Our work is telling us that the earliest bony fishes looked pretty much like sharks, and not vice versa. What we might think of as shark space is, in fact, general modern jawed vertebrate space."
The study began with a new analysis of the well-preserved acanthodian, Acanthodes bronni. Co-author Samuel Davis created highly detailed latex molds of specimens revealing the inside and outside of the fossil's skull, which could be used to assess cranial and jaw anatomy as well as the organizations of sensory, circulatory and respiratory systems in the species. The analysis of the molds combined with recent CT scans of skulls from early sharks and bony fishes led the researchers to a surprising reassessment of what Acanthodes bronni tells us about the history of jawed vertebrates.
"For the first time, we could look inside the head of Acanthodes, and describe it within this whole new context," Coates stated. "The more we looked at it, the more similarities we found with sharks."
Analysis of the evolutionary relationships of Acanthodes bronni even with the new data added still connected this species to early bony fishes. Meanwhile, some other acanthodian species turned out to be primitive sharks, while others were relatives of the common ancestor of sharks and bony fishes.