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  • Writer's pictureLeaf

This random bird went extinct and now it’s back. What?! How?

How can a species just come back from extinction like that?! These birds have returned to the land of the living through a process called re-evolution, or iterative evolution, in which a distinct population is wiped out from an area, but it is recolonized by members of the source population, who evolve in the same way as the extinct population. Let’s unpack that!

What/who is this bird? Where did it come from? This is the Aldabra rail, a subspecies of the white-throated rail (Dryolimnas cuvieri), which is indigenous to islands in the southwestern Indian Ocean. The flightless rail or Aldabra rail is a descendent of a flying bird species known as the white-throated rail.

Well, how did it go extinct? The Aldabra rail was wiped off when the island submerged beneath the water approximately 136,000 years ago. When the sea levels fell again, a few thousand years later, the fossils some scientists found reveal that the species re-colonized the island, losing the ability to fly owing to the island's lack of predators. This would be the second time the Aldabra rails have lost their ability to fly, due to this being their second time evolving into existence, all through iterative evolution.

Wait, so it’s the exact same bird species? Absolutely! The scientists who studied these birds were shocked too, leading them to check out these re-evolved birds’ bones against the bones of the ones that went extinct. They found that the pre-flood specimens are very similar to the bones of the flightless rails that exist on Aldabra today. And the leg bone belonging to a rail that lived on Aldabra in the immediate post-flood period suggests that the bird was losing its flight—or, in other words, that virtually the same subspecies was evolving on Aldabra for the second time. WOW that’s so cool!!

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