'Walking fish' unveil mystery of human evolution on land 400 million years ago

A new study has explained how 'walking fishes' walked on land and helped humans evolve about 400 million years ago.

Researchers at McGill University, turned to a living fish, called Polypterus, an African fish that can breathe air, 'walk' on land and similar to the ancient fishes that evolved into tetrapods, to help show what might have happened when fish first attempted to walk out of the water. The team raised juvenile Polypterus on land for nearly a year, with an aim to revealing how these 'terrestrialized' fish looked and moved differently.

The fish showed significant anatomical and behavioural changes. The terrestrialized fish walked more effectively by placing their fins closer to their bodies, lifted their heads higher, and kept their fins from slipping as much as fish that were raised in water.

Trina Du, a study collaborator said that anatomically, the pectoral skeleton of the fishes changed and became more elongated with stronger attachments across their chest, possibly to increase support during walking, and a reduced contact with the skull to potentially allow greater head/neck motion.

Hans Larsson, Canada Research Chair in Macroevolution at McGill, added that since many of the anatomical changes mirror the fossil record, it can be hypothesized that the behavioural changes also reflect what may have occurred when fossil fish first walked with their fins on land.

The unique terrestrialized Polypterus experiment provides new ideas for how fossil fishes may have used their fins in a terrestrial environment and what evolutionary processes were at play.

The study is published in the journal Nature.