The discovery of fossils from a prehistoric fish, Euphanerops, with fins near its butt shed light on human evolution and more specifically, why humans have two arms and two legs.
Euphanerops is a 370-million-year-old species and is believed to be the first creature to develop paired appendages, according to the study that was published in the journal Biology Letters.
"Fins are the world's first limb-like appendages," the study's lead author and researcher at the University of Leicester and University of Manchester Robert Sansom told Discovery News.
"Paired limbs would subsequently develop from paired fins in the transition from sea to land, but the first evolution of paired appendages was a big, important step in the evolution and development of vertebrates."
The fossil specimens were discovered in Quebec, Canada by Sansom and colleagues Sarah Gabbott and M.A. Purnell. The team of researchers studied 36 Euphanerops specimens of the jawless fish species that predate dinosaurs and found that unlike other fish that have a solo fin near their butt, this species seemed to evolve into having two of these anal fins.
"What this research leads us to believe is that, at this early stage (in evolutionary history), vertebrates were trying out lots of different body plans, some familiar, some less familiar, and only some that survived," Sansom said.
Sansom believes that the second anal fin is probably related to better efficiency with movements.
"The evolution of paired appendages and more sophisticated fins will probably be for improved locomotion, potentially related to an arms race between tracking down prey and avoiding predators," Sansom said.
"Paired fins allow for more sophisticated control of movement."
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