When an animal species is pushed to the brink of extinction, it is often powerless,media BGR reported. This is the case on TheArdabra Atoll, where a medium-sized bird that does not fly and is about the size of a chicken died out about 136,000 years ago. Aldabra Atoll was submerged by rising seawater, and the non-flying birds could not escape, and the entire species was wiped out.
Extinct species usually do not appear again. In a rare and incredibly interesting twist, however, when Aldabra Atoll reappeared, only about 30,000 years later, the flying bird reappeared. The researchers believe that, due to the lack of predators and abundant food on the island, the bird, known as diphtheria, gradually lost its ability to fly over time and became a ground-based bird.
When Aldabra Atoll surfaced from the deep sea, the diphtheria chicks moved in again, like a re-enactment of evolution, and the birds that remained there evolved again to lose their ability to fly. The researchers demonstrated this by comparing fossils before and after the extinction event on The Ardabra Atoll. Diphtheria chicks without flying ability can still be found on the island today.
“These unique fossils provide irrefutable evidence that a member of the diphtheria family colonized the atoll, most likely from Madagascar, and independently became a flying bird each time,” lead researcher Dr. Julian Hume said in a statement. “The fossil evidence presented here is unique to diphtheria chicks and epitomizes the successful colonization of isolated islands by these birds and the multiple evolutions into incapacity to fly. “
Scientists call it “re-evolution” and, quite rarely, allow a species to evolve twice, especially in such a short period of time. “What we do know is that there are no other examples of diphtheria or birds in general that are so obvious evidence of this phenomenon, ” said study co-author Professor David Martill. “There are the oldest paleontological records of any of the ocean islands in the Indian Ocean region, but only on the island of Aldabra has fossil evidence of the effects of sea level changes on extinction and recolonization. “