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A bird that previously went extinct has reappeared after evolving all over again, scientists have discovered.

The Aldabra rail reappeared on a small island in the Indian Ocean, off the south-east coast of Africa, where it lived.

The flightless bird is a descendent of the flying white-throated rail.

It's thought it became flightless over the years because it had no predators on the ground and plenty of food for it, so there was no need to develop those wing muscles.

The Indian Ocean was once home to a lots of flightless birds - the most famous being the dodo - but as humans arrived these birds became extinct.

When the island was completely covered by the ocean, almost all life on it was wiped out.

However Dr Julian Hume and his team, from the Natural History Museum, found fossils of the bird from 136,000 years ago. And then from 118,000 years ago.

That means that once the bird became extinct, it only took 20,000 years for the white-throated rail to return AND evolve into the flightless Aldabra rail bird again.

This is one of the fastest known timelines of a bird losing its ability to fly.

"There is no other case that I can find of this happening," says Julian, "where you have a record of the same species of bird becoming flightless twice."