The unstoppable birds died out on a group of islands and then evolved again

Birds unable to fly and living on a group of isolated coral islands have totally disappeared more than 100,000 years ago. Now, birds unable to fly live there, having evolved from the same ancestral species.

Researchers at the Natural History Museum in the United Kingdom and the University of Portsmouth drew this conclusion by examining the fossil record of Aldabra Atoll – a group of four coral islands in the Indian Ocean. Their discoveries were published this week in the Zoological Journal of the Linnean society.

The Aldabra Atoll is home to the Aldabra Rail, a flightless bird that descends from the white-throated rail. A white-throated rail – which can fly – is a bird the size of a chicken, native to Madagascar, but known to travel to and visit other isolated islands, says one. press release from the University of Portsmouth.

The white-groove tracks leading to the Aldabra atoll finally evolved in such a way that they lost their ability to fly, which they no longer needed because they had no predators. This, however, became a major disadvantage when the atoll disappeared below sea level about 136,000 years ago, killing the animals and plants that lived there, including the leak-free rails.

But about 100,000 years ago, the sea level fell again and the rails unable to fly finally reappeared on the atoll. Scientists say the fossil record indicates that white-railed rails have once again colonized the island and have again become a subspecies unable to fly.

"These unique fossils provide irrefutable evidence that a member of the railroad family colonized the atoll, probably in Madagascar, and became unable to fly at every opportunity," said the researcher. Chief Julian Hume of the Natural History Museum in a statement.

The researchers say that this is a significant occurrence of iterative evolution – meaning that similar characteristics are changing repeatedly from the same ancestor at different times. As Vice News notes, scientists have observed the phenomenon in animals such as sea cows and sea turtles. But Portsmouth University professor David Martill, co-author of the study , said that it was the most obvious example of the ongoing process in birds.

"We do not know of any other example in the rails, or birds in general, that demonstrates this phenomenon so obviously," he said.