By Yasemin Saplakoglu
On a ring-shaped reef in the Indian Ocean, a species of bird evolved to be flightless — twice.
Hundreds of thousands of years ago, white-throated rails (Dryolimnas cuvieri) flew from their native home in Madagascar to the Aldabra atoll, a ring-shaped reef among the Seychelle Islands. The reef, free of predators for the birds, was a comfortable place to call home — and as time passed, the rails lost their ability to fly.
But catastrophe struck about 136,000 years ago, when a major flood swept the atoll — and the flightless birds — beneath the waters of the Indian Ocean, leading to the birds’ extinction.
But not all was lost: About 36,000 years after that, when the world was in the clutches of an ice age, sea levels fell, and the atoll reappeared at the water’s surface. And after a while, something familiar happened: The antsy white-throated rails took off again from Madagascar and flew to the atoll. Sometime after that, the birds, once again evolved out of their ability to fly.
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