Anal Fin Discovery May Offer Insight Into Human Evolution

Looking back in time an estimated 400 million years, the Earth was experiencing an era known as the Age of Fishes - a name it earned due to the rapid expansion of fish species that took place during it. As a result of this seemingly constant change, something important happened - not just for fish but creatures everywhere: jawless fish split from jawed vertebrates.

And it's to this crucial evolutionary period (370 million years ago, to be exact) that Robert Sansoms of the University of Manchester places his discovery of a fossilized fish called the Euphanerops that, he believes, sheds light into not only the evolution of fish, but of humankind.

Found in Quebec, Canada, Sansom used a 3D surface scan of the fossil and found that there was something strikingly different about it from others like it: instead of just one anal fin, the fossil showed that the fish had two.

"Up until now anal fins have only been seen on jawed fish where they are unpaired and this is true of both extinct and modern fish," Sansom explained in a press release. He then added that given the important break between jawed and jawless fish during this period, the discovery "represents an important stage in the evolution of paired appendages."

In fact, while the scientist explained he doesn't understand the purpose of the dual anal fins, their presence may mean a lot in terms of the way many species are formed today.

"It's not clear why the fins are positioned so far back on the fish, or what advantage they might have provided," he said. "However, they do show that our early vertebrate ancestors tried out lots of different body plans before settling on two arms and two legs. If they hadn't, then our bodies would have looked very different!"

In addition to shedding further light on the evolution of paired appendages (fins, legs, arms, etc.), Sansom said the fossil is evidence of "a large amount of developmental plasticity during this episode." 

Knowing this, Sansom said, will likely effect how scientists view the "timing and sequence of events underlying the origin and diversification of vertebrate appendages."