It sounds like a child’s story — a fish who was born with legs and had to overcome his differences in the fish community, learning to walk and expanding his world as a result. But the African Polypterus — a real fish with both lungs and gills — is providing pivotal insight into evolution, and our own biologic history.

Researcher at McGill University (no joke) in Canada have been raising Polypterus for a year, changing the fish’s environment by taking them out of the water, and seeing how they responded. The fish adapted to the environment and began to walk more effectively than fish raised in water. The land-locked fish lifted their heads higher and snapped their fins to their bodies. Their skeletons even changed as they were forced to walk more.

The findings show how our ancestors, millions of years ago, may have first ventured onto land, eventually evolving into the thousands of animal species on Earth — and us.