If we set out to list animal species close to humans, it would surely take us to conclude that the shark once shared a common ancestor with us. Now, it is the first time that there is evidence of this ancestor.
A team of researchers from the University of Chicago, University College Dublin and the University of Cambridge has found evidence suggesting that humans and sharks shared a common ancestor about 440 million years ago.
The finding has been produced from the study of a 385-million-year-old shark fossil.
When this fossil was found, in 2001, it was first believed that the shark lacked teeth, and for that reason, scientists gave it the name Gladbachus adentatus.
But now, years later and after a new effort, the researchers carried out a much more exhaustive study of the remains, and in doing so, discovered that, in reality, it represented a kind of transition between Acanthodians and Chondrichthyes. A short piece of evidence that offered a better picture of a period of time for which there are few fossil records.
The evidence suggests a new estimate of the time during which humans and sharks shared a common ancestor, approximately 440 million years ago.
The specimen is the only one of its kind found: that of a shark that lived approximately 385 million years ago, during a period known as Devonian, which lasted from 416 million to 358 million years ago.
The first vertebrate being with jaw
Being the first vertebrate living being with jaw, it constitutes the first ancestor, not only of all the fish, but also of the mammals and, therefore, of the humans.
The remains consisted of three sections, all flat compressed in resin. The resin shell retained much of the endoskeleton, allowing the team to collect tissue samples. The teeth, the skull, the cartilage and the details of the gills were also preserved.
The researchers note that the body of the specimen looked like a sheet of scales and that the bones in its head were very rough.
The researchers also point out that even though the study has clarified part of the shark’s evolutionary history, it has also complicated the understanding of its lineage: they found evidence suggesting that the evolution of sharks has many branches , several of which seem to converge, leading to the characteristics found in modern sharks, such as the long gullet and the multiple gill slits.
His study also confirmed that Gladbachus adentatus actually had a large number of teeth, both small and large.