Tuesday 14 May 2019

Creationism Goes off the Rails

Aldabran White-throated rail, Dryolimnas cuvieri subsp. aldabranus.

Photo credit: Charles J Sharp [CC BY-SA 4.0]
The bird that came back from the dead | UoP News

Here we have a very nice example of how evolution is 'directed' by the environment, and an example of how the Theory of Evolution has explanatory powers that creationism simply does not have. This example is of a flightless member of the rail family of birds that evolved not once but twice on the small Indian Ocean atoll of Aldabra.

Julian P Hume of the Bird Group, Department of Life Sciences, Natural History Museum, Tring, Herts, UK and David Martill of the School of Earth and Environmental Sciences, University of Portsmouth, Portsmouth, UK, have shown that the present day flightless white-throated rail of Aldabra has some strikingly similar features to an extinct flightless rail. The extinct rail inhabited the atoll until climate change caused the sea level to rise and cover the atoll about 136,000 years ago, exterminating all plant and animal life.

Their findings were published a few days ago in the Zoological Journal of the Linnean Society. Regrettably, the full paper is behind an expensive paywall.

As the University of Portsmouth press release explains:

Wing bones fossils of flighted (right) and flightless Dryolimnas rails.
The white-throated rail is a chicken-sized bird, indigenous to Madagascar in the south-western Indian Ocean. They are persistent colonisers of isolated islands, who would have frequent population explosions and migrate in great numbers from Madagascar. Many of those that went north or south drowned in the expanse of ocean and those that went west landed in Africa, where predators ate them. Of those that went east, some landed on the many ocean islands such as Mauritius, Reunion and Aldabra, the last-named is a ring-shaped coral atoll that formed around 400,000 years ago.

With the absence of predators on the atoll, and just like the Dodo of Mauritius, the rails evolved so that they lost the ability to fly. However, Aldabra disappeared when it was completely covered by the sea during a major inundation event around 136,000 years ago, wiping out all fauna and flora including the flightless rail.

The researchers studied fossil evidence from 100,000 years ago when the sea-levels fell during the subsequent ice age and the atoll was recolonised by flightless rails. The researchers compared the bones of a fossilised rail from before the inundation event with bones from a rail after the inundation event. They found that the wing bone showed an advanced state of flightlessness and the ankle bones showed distinct properties that it was evolving toward flightlessness.

This means that one species from Madagascar gave rise to two different species of flightless rail on Aldabra in the space of a few thousand years.

As lead author and avian palaeontologist, Dr Julian Hume, pointed out:

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. 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.

The same species, on two separate occasions, when if found itself in the same environment, evolved in the same direction with a high degree of convergence. An example of what the authors call ‘iterative evolution’. Of course, this was not, as the popular press have portrayed it, an example of an extinct species coming back from the dead, but an example of two different species evolving from the same ancestor in the same environment. What would be interesting would be a comparison of the genomes of these pre and post climate change populations to see whether the same variations of the same genes were responsible for convergence or whether the same result came from different evolutionary pathways.

This convergence is exactly what we would expect from the ToE where the environment naturally selects those variants which are more suited to survival and replication in it. In the case of these rails on a small Indian Ocean atoll, free from terrestrial predators, the local environment pre and post inundation due to climate change favoured flightlessness and this was achieved by selecting from the available variations.

The only plausible creationist explanation is that a supposedly intelligent designer make a stupid mistake in exterminating the earlier population of flightless rails on Andaman Atoll and decided to redo its earlier design.

Creation by blunder and incompetence - if you believe that superstitious nonsense.

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