We’re all related…to fish!

Most of us know that humans evolved from apes and that apes evolved from creatures that came from the sea.

But now scientists believe they have found the missing link; a type of fish that had primitive legs. It’s one of the earliest forms of – us – ever discovered.

So next time you take your fishing gear for a day on the riverbank, spare a thought for your relatives. And no, we’re not talking about your long suffering partner, we mean your (very) distant cousins, the fish.

The Tiktaalik

tiktaalik model

A model version of a Tiktaalik
Source: University of Chicago

A new study of 375 year old fossils dug up in Northern Canada in 2006 has revealed a fish with ambition – the tiktaalik. Not content to spend its days swimming, this crocodile-like fish had spiracle holes in its skull – nostrils – pointing to the presence of primitive lungs and a skeletal system similar to some of today’s land animals.

The Tiktaalik’s front fins had elbows and an early form of wrist joint and at the other end, the fish’s pelvic girdle was much heavier than that of its contemporaries indicating that it might have had back fins a bit like legs. This four limbed propulsion could have seen the fish ‘walking’ through the shallows and maybe even shuffling out onto the mudflats.

This is completely new because up until now, scientists thought creatures didn’t begin to grow back legs until they had already moved to the land.

Missing link

Tiktaalik fossil

The missing ‘in between stage’ link
Source: Wikimedia

The unearthing of  the tiktaalik is the holy grail for those with a passion for prehistoric life. As Jennifer Clack of Cambridge University’s fossil museum said in an interview with the Boston Globe: “It’s what we’ve all been waiting for.”

The discovery is being trumpeted as the long looked for ‘in between stage’ when the pelvic fins of fish developed. During this time, they became much larger and stronger and eventually evolved into the hind limbs of four legged land creatures, including mammals that eventually stood up and became us.

Defence mechanism

Mudskippers

Mudskippers have similar limbs to Tiktaalik
Source: Wikipedia

Paleontologists studying the prehistoric creature’s fossilised remains say its ungainly proportions and short, stubby fins suggest the fish was highly specialised to a shallow, muddy environment and would have moved in a similar way to a modern mudskipper.

In open water the tiktaalik would have been an easy lunch for other fish, a fact that has prompted scientists to speculate that the development of early limbs was a defence mechanism. Legs would have enabled the tiktaalik to squirm into ever shallower waters to evade predators. And eventually through evolution its descendents escaped from the water altogether.

Chance discovery

arctic

Discovered after a trip to the Arctic
Source: City Connect

Like so many breakthroughs, the discovery of the tiktaalik owes much to chance. The rock containing the fossil was loaded onto a helicopter at the end of a trip to the Arctic. It wasn’t considered to be of high priority, until that is, it was found to contain the fossilised remains of the creature that links land and sea life.

A second trip to the same area produced another fragment of pelvis, but not as was hoped, an entire rear fin. Now researchers plan to turn their attention to another area of the Arctic to study even older rocks to see if they can trace the origins of fish.

So next time you cast, wade or walk, just think, you have more in common with your quarry than you might previously have thought. Those arms and legs of yours used to be fins.