This bird has evolved to exist twice – thousands of years apart

On a ring-shaped reef in the Indian Ocean, a bird evolved to become unable to fly – twice.

There are hundreds of thousands of years, white-throated rails (Dryolimnas cuvieri) flew from their country of origin to Madagascar to Aldabra Atoll, a ring-shaped reef located in Seychelles. The reef, free of predators for birds, was a comfortable place to go home – and over time, the rails lost their ability to fly.

But the disaster struck about 136,000 years ago, when a major flood swept the atoll – and birds that do not fly – under the waters of the Indian Ocean, resulting in extinction of these birds. [Photos of Flightless Birds: All 18 Penguin Species]

But not all was lost: about 36,000 years later, as the world was plunged into an ice age, the sea level dropped and the atoll reappeared on the surface of the water. And after a while, something familiar happened: the white-necked nerve rails left Madagascar and headed for the atol. Some time later, birds once again evolved in their ability to fly.

This means that a single species, the white-throated rail, has evolved to become unable to fly twice – a phenomenon called "iterative evolution," according to a statement from the University of Portsmouth.

Scientists from the University of Portsmouth and the Natural History Museum, both located in the UK, came to this conclusion by comparing the bones of the old Aldabra-free rails – both those that existed before and after the Flood – to newer birds. This includes the more modern bones of the flying rails and the no-flight rails Aldabra (Dryolimnas cuvieri aldabranus) who still live on the atoll today.

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The team discovered that the bones of the Aldabra rails prior to the flood were very similar to the modern Aldabra rail bones.

In addition, the researchers found that the bones of the wing and ankle, which date back to about 100,000 years ago, or about the time the birds flew again to the atoll after l '. flood, have shown that animals evolved towards lack of flight. Specifically, the ankle bone was stronger compared to the same ankle bone in flying birds, suggesting that the birds were becoming heavier and losing their ability to fly, according to the UK National History Museum .

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

As for why these rails left Madagascar in the first place, it is still uncertain. However, every 50 to 100 years or so, factors such as overcrowding or declining food supply cause massive migration of birds from Madagascar in all directions of the Indian Ocean, according to the National History Museum. The lucky ones end up finding an island to their liking.

The researchers published their findings on May 8 in the Zoological Journal of the Linnaeus Society.

Originally published on Science live.