In nature, evolution is a rather magical process, because only those species that can adapt to environmental changes can thrive over long periods of time. Recently, however, scientists have unveiled an interesting study revealing the "regression" of a certain bird. About 136,000 years ago, a flightless bird on an island in the Indian Ocean went extinct. However, tens of thousands of years later, they have evolved back.
White-throated rail infographic, by Charles J Sharp (CC BY-SA 4.0)
Scientists point out that under the influence of environmental pressures, sometimes evolution becomes a predictable process. After a species goes extinct, it is not surprising that some new species with very similar characteristics may appear in the same place in the future.
In short, evolution basically follows a process in which the end result should be similar if you put similar ingredients in the same way — and this recurrence is called iterative evolution.
A new study published in the Linnaean Journal of the Linnean Society recently pointed to a similar incident on aldabra, a ral reef atoll in northern Madagascar.
The fossil record shows that at some point 400,000 years ago, the white-throated rail, a bird native to Madagascar, once ruled the island.
With no predators, the diphtheria buzzard soon became unable to fly. So when sea levels rose about 136,000 years ago, the entire island was completely submerged, leading to the extinction of many species, including the white-throated buzzard.
On the right side of the picture above is a fossil wing bone of a flying buzzard (From: University of Portsmouth)
Interestingly, the story doesn't end there. Because about 100,000 years ago, due to the decline in sea level during the Ice Age, the island was fortunate to see the light of day.
The white-throated buzzards that migrated from Madagascar to there again had a good life without predators, only to become unable to fly again – a strong case of iterative evolution!
The team analyzed the bones of the white-throated buzzards (wing bones and ankle bones) before and after the island submergence and found that they were indeed evolving towards a non-flying body type.
Lead researcher Julian Hume said: "These unique fossils provide irrefutable evidence that members of the white-throated buzzard family that later ruled the island were most likely from Madagascar and were not always able to fly independently.
Fossils are unique in their proof of iterative evolution of the diphthered buzzard and reflect the ability of these birds to evolve to flightless appearances on many different occasions after successfully dominating an isolated island.