This bird evolved into existence twice: thousands of years apart –

This bird evolved into existence twice: thousands of years apart


This bird evolved into existence twice: thousands of years apart

A white throat lane (Dryolimnas cuvieri)

Credit: Charles J Sharp [CC BY-SA 4.0]

On a ring-shaped reef in the Indian Ocean, a species of bird evolved not to fly, twice.

Hundreds of thousands of years ago, white-throated rails (Dryolimnas cuvieri) flew from his native home in Madagascar to the Aldabra atoll, a ring-shaped reef between the Seychelles. The reef, free of predators for birds, was a comfortable place to call home, and with the pbadage of time, the rails lost the ability to fly.

But the catastrophe occurred approximately 136,000 years ago, when a great flood swept the atoll, and birds that do not fly, under the waters of the Indian Ocean, which led to the extinction of the birds. [Photos of Flightless Birds: All 18 Penguin Species]

But not all was lost: approximately 36,000 years later, when the world was in the grip of an ice age, sea levels dropped and the atoll reappeared on the surface of the water. And after a while, something familiar happened: the white-throated rails took off again from Madagascar and flew towards the atoll. Some time after that, the birds, once again, evolved out of their ability to fly.

This means that a single species, the white-throated rail, evolved not to fly twice, a phenomenon known as "iterative evolution," according to a statement from the University of Portsmouth.

Scientists from the University of Portsmouth and the Museum of Natural History, both in the U.K., came to this conclusion when comparing the bones of the old non-flying Aldabra rails, both those that existed before and after the flood, with more recent birds. That includes the more modern bones of the flying rails and the non-flying Aldabra rails (Dryolimnas cuvieri aldabranus) that still live in today's atoll.

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Wing of non-flying bones (left) and flown (right) Dryolimnas rails

Credit: Julian Hume

The team discovered that the bones of the Aldabra rails dating from before the flood were very similar to the bones of modern Aldabra rails.

In addition, the researchers discovered that the bones of the wing and ankle dating back approximately 100,000 years ago, or at the time the birds flew back to the atoll after the flood, showed evidence that the animals were evolving into the absence Of flight. Specifically, the ankle bone was stronger compared to the same ankle bone in flying birds, suggesting that birds were becoming heavier and lost their ability to fly, according to the US National Museum of History. UU

"These unique fossils provide irrefutable evidence that a member of the railroad family colonized the atoll, probably from Madagascar, and became an independent flightless on each occasion," said lead researcher Julian Hume, avian paleontologist at the Museum of History. Natural, in the statement. .

As to why these rails left Madagascar in the first place, it is still not clear. But every 50 or 100 years, factors such as overpopulation or declining food supplies cause mbadive migration of birds from Madagascar in all directions across the Indian Ocean, according to the National History Museum. The lucky ones end up finding an island to their liking.

The researchers published their results on May 8 in the Zoological Journal of the Linnean Society.

Originally published in Living science.

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