A bird thought to have evolved away from being flightless thousands of years ago is once again unable to fly, researchers have discovered.
The white-throated rail is a chicken-sized bird, native to Madagascar, that lives in tropical or subtropical moist lowland and mangrove forests.
It's an impressive feat possible through a phenomenon known as "iterative evolution", which refers to the repeated evolution of the same structures from a single ancestor at different times.
He continued and explained that "Fossil evidence presented here is unique for rails, and epitomizes the ability of these birds to successfully colonize isolated islands and evolve flightlessness on multiple occasions".
The Natural History Museum in the United Kingdom has found the last surviving native flightless rail on Aldabra in the Seychelles, 390 miles east of Tanzania in the Indian Ocean.
Aldabra is a ring shaped coral island, referred to as an atoll, near the coast of Madagascar.
Scientists found fossil evidence of the flightless rail on Aldabra dating back 136,000 years in research published in the Zoological Journal of the Linnean Society. The Aldabra rail found its way back to the island once the water had receded.
Researchers from the University of Portsmouth and London's Natural History Museum discovered that a species of rail bird successfully colonised a small island called Aldabra and became flightless, then died out and then the whole process happened again. There were no predators on the atoll, rendering the birds' ability to fly unnecessary-so they lost it.
Unfortunately, that gave them no means of escape when the island was submerged and all its flora and fauna were wiped out.
The Aldabra rail is commonly thought to be the last flightless bird living in the Indian Ocean.
"Only on Aldabra, which has the oldest palaeontological record of any oceanic island within the Indian Ocean region, is fossil evidence available that demonstrates the effects of changing sea levels on extinction and recolonization events", Martill said.
David Martill, a co-author of the study, said they are aware of no other case of rails or birds for the most part, who've shown the marvel of iterative evolution.
"These unique fossils provide irrefutable evidence that a member of the rail family colonized the atoll, most likely from Madagascar, and became flightless independently on each occasion", lead researcher Julian Hume, avian paleontologist and research associate at the Natural History Museum, said in a statement.
However, those that flew east could reach one of the many neighbouring islands, which include Mauritius - famously once home to another flightless bird, the dodo - Reunion and the Aldabra islands.
Furthermore, the scientists have analyzed the fossils from and before the flooding event, and the Rails' wings are showing signs of an advanced state of flightless and the ankle bones are confirming the fact of flightless.