A once-extinct bird species "re-evolved" itself into existence and returned to the island it once colonized thousands of years ago, researchers say.

The Aldabra rail, named after the Aldabra Atoll it inhabits in the Seychelles, is the last surviving native flightless bird in the Indian Ocean region. It is a descendant of the flying white-throated rail that is believed to have lost its ability to fly because the lack of predators made it unnecessary.

Fossils of the Aldabra rail have been discovered dating back 136,000 years, but the island has since been submerged by the ocean, wiping out almost all life.

"Aldabra went under the sea and everything was gone," Julian Hume, paleontologist and author of the study, said in a press release from the Natural History Museum in London. "There was an almost complete turn over in the fauna. Everything … went extinct. Yet as the Aldabra rail still lives on today, something must have happened for it to have returned."

The research, published in the Zoological Journal of the Linnean Society , revealed that the white-throated rail recolonized the islands. But researchers believe that after the sea levels dropped and the bird reappeared, it became flightless once again. Newer fossils showed the Aldabra rail was heavier than its ancestor, indicating that the bird had lost its ability to fly for a second time.

Once the bird became extinct after the flood, it took only 20,000 years for the white-throated rail to return and evolve into the flightless Aldabra rail bird again. According to the museum, this is one of the fastest recorded timelines of a bird losing its ability to fly, and the first and only known time that a species of bird has become flightless twice.

"There is no other case that I can find of this happening, where you have a record of the same species of bird becoming flightless twice," Hume said in the release. "It wasn't as if it were two different species colonizing and becoming flightless. This was the very same ancestral bird."

