How 'walking' fish helped mammals evolve

Ever imagined how fish "walked" out of the water for the first time to eventually evolve into today's mammals?

To unlock the mystery, Canadian researchers turned to a living fish called Polypterus to explain what might have happened when fish first attempted to "walk" out of the water.

Around 400 million years ago, a group of fish began exploring land and evolved into tetrapods - today's amphibians, reptiles, birds and mammals.

The team raised juvenile Polypterus, an African fish that can breathe air, 'walk' on land and looks much like those ancient fishes that evolved into tetrapods.

The aim was to reveal how these "terrestrialised" fish looked and moved differently.

They found that "terrestrialised" fish walked more effectively by placing their fins closer to their bodies and lifted their heads higher.

"Because many of the anatomical changes mirror the fossil record, we can hypothesise that the behavioural changes we see also reflect what may have occurred when such fish first walked with their fins on land," explained Hans Larsson from McGill University.

The experiment provides new ideas for how those fishes may have used their fins in a terrestrial environment and what evolutionary processes were at play, said the study which appeared in the journal Nature.