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Between 136,000 and 240,000 years ago, a flock of troublesome long-legged birds took off from Madagascar and arrived at a pristine island of Aldabra Atoll, 250 km away. "That's fine," they would have thought – there were no predators and the birds colonized the island. Without the threat of predation, they eventually lost their ability to fly. But 136,000 years ago, a flood swept the island, annihilating this unique species, unable to fly.
Some time later, another group took off from Madagascar and arrived at Aldabra – and the evolution proceeded almost in the same way.
The rails are a family of flying birds that you could see creeping into the swamps, and some railroad species are known to disperse far enough from their original homes. It is not surprising that the white-sided railway species colonized a distant island – but a new document perhaps documents the first case of the same kind of railway colonizing the same island and then evolving on the same path.
"The fossil evidence presented here is unique for [rails] The authors Julian Hume of the Natural History Museum and David Martill of the University of Portsmouth write in the recently published study in the Zoological Journal of the Linnaean Society.
The researchers analyzed fossils of wings and legs taken from the island and preserved at the National Museum of Natural History of the United States at the Smithsonian Institution and the Natural History Museum of the United States. London. According to the newspaper, this island has the oldest paleontological record of all the islands in the Indian Ocean. They compared the fossilized bones to specimens of white-throated rails at the Natural History Museum in Tring, some from Malagasy birds capable of flying and some other Aldabran birds that had evolved so that they could no longer fly.
The fossilized bones had almost the same measures as the bones of Aldabran birds unable to fly, according to the newspaper. Essentially, the wing bones were stunted and the bones of the legs thicker, implying that the old rail was also a bird unable to fly. There is fairly strong evidence that the Aldabran Islands were completely submerged 136,000 years ago, which would have wiped out the older rail population. But it seems that another population of rails has come back and evolved in the same way, figuratively and perhaps literally, on the same path as their predecessors.
Let me take a moment to describe the rails. They are usually clumsy birds with large legs that spend most of their time walking. They can not seem to fly and they look hilarious when they do. They are also known to have scattered from far away – they stop flying when they find a nice place. According to one article, rails unable to fly are "one of the richest examples of parallel evolution of vertebrates". But the same kind, colonizing the same island and moving in the same direction? This seems to be a first.
Other researchers were impressed by the work. "It's a very elegant analysis," Martin Stervander, a postdoctoral researcher at the University of Oregon who was not involved in the study, told Gizmodo. "The two fossils look a lot like the rails today. We can clearly see that it is railway fossils and that they were unable to fly. "
But the story has a darker side. The Aldabra rail is the last surviving bird unable to fly in the Indian Ocean. "They are more vulnerable to extinction when they are unable to fly," Julia Heinen, a doctoral student at the University of Copenhagen, told Gizmodo. "They do not have the habit of having predators. Then, when people arrive with rats and cats and everyone loves to eat birds, they can not fly away and turn off much faster. According to one estimate, between 440 and 1580 species of oars unable to fly died out after human colonization in Oceania.
As long as cats and rats remain on these islands, it is unlikely that these re-evolutionary events will happen again.
Selected image: Francesco Veronesi (Wikimedia Commons)
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