A recent study reveals that a bird species who went extinct 136,000 years ago, has now re-evolved. This type of rail, called Aldabra has technically rose from the dead thanks to a rare process called ‘iterative evolution’.
The research, from the University of Portsmouth and Natural History Museum, found that on two occasions, separated by tens of thousands of years, a rail species was able to successfully colonise an isolated atoll called Aldabra and subsequently became flightless on both occasions. The last surviving colony of flightless rails is still found on the island today.
The study, published in the Zoological Journal of the Linnean Society, indicates that this is the first time that iterative evolution (the repeated evolution of similar or parallel structures from the same ancestor but at different times) has been seen in rails and one of the most significant in bird records.
“These unique fossils provide irrefutable evidence that a member of the rail family colonised the atoll, most likely from Madagascar, and became flightless independently on each occasion,” lead researcher Dr. Julian Hume, avian paleontologist and research associate at the Natural History Museum, said in a statement. “Fossil evidence presented here is unique for rails, and epitomises the ability of these birds to successfully colonise isolated islands and evolve flightlessness on multiple occasions.”
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Researchers found fossil evidence proving the flightless Aldabra rail went extinct when their island flooded 136K years ago… and evolved back when new birds colonized the island years later. pic.twitter.com/sCYaqNubJx
— AJ+ (@ajplus) May 10, 2019
As flying was unnecessary to avoid predators, this also indicates the birds had no way to escape their native island once sea levels began to rise. However, unlike the famous Dodo of Mauritius, the rails were able to re-emerge from Madagascar once sea levels lowered again, CBS News reports.
Co-author Professor David Martill, from the School of Earth and Environmental Sciences at the University of Portsmouth, said: “We know of no other example in rails, or of birds in general, that demonstrates this phenomenon so evidently. Only on Aldabra, which has the oldest palaeontological record of any oceanic island within the Indian Ocean region, is fossil evidence available that demonstrates the effects of changing sea levels on extinction and recolonisation events.
“Conditions were such on Aldabra, the most important being the absence of terrestrial predators and competing mammals, that a rail was able to evolve flightlessness independently on each occasion.”