Posts Tagged ‘Marsupials’

The Flightless Bird So Good It Evolved Twice

May 12, 2019

Another fascinating piece of news in yesterday’s, for 11th May 2019, was about the discovery by evolutionary scientists that a type of flightless bird had evolved twice on the same Indian Ocean atoll. It reappeared the second time thousands of years after it had first come extinct, in a process biologists call ‘iterative evolution’. The article, ‘Evolution strikes twice for flightless bird on isolated atoll’, by Ben Mitchell, reads

A flightless bird that became extinct when its home island became flooded by the sea “came back to life” when a similar species evolved in the same location, scientists have discovered.

Researchers from the University of Portsmouth and the Natural History Museum found that a species of rail colonised an isolated atoll called Aldabra in the Indian Ocean on two occasions separated by tens of thousands of years. On both occasions, the white-throated rail evolved independently to become flightless. The last surviving colony of the flightless rails is still found on the island.

A University of Portsmouth spokesman said: “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. 

The co-author of the study in the Zoological Journal of Lennean Society, Professor David Martill of the University of Portsmouth, said: “We know of no other example that demonstrates this phenomenon so evidently.”

How fascinating! It sounds similar to the phenomenon of parallel evolution, in which unrelatedly creatures develop similar features through occupying similar ecological niches. One example is the way penguins have evolved features similar to other marine creatures like whales and fish, with their wings becoming flippers. Another example is the thylacine, the marsupial wolf, otherwise known as the Tasmanian tiger. This creature is, unfortunately, now extinct, as it was hunted down as a pest by the Australian farmers. Although it was a marsupial, and had evolved independently in Australia over millions of years, it was remarkably like a European wolf. There was speculation at one time that the different human races were also the result of parallel evolution around the world, each evolving separately from common hominid ancestors. This has since been rejected, not least because it’s considered to be more than a little racist, somehow suggesting that the different varieties of modern humanity are biologically different species.

The palaeontologist Simon Conway-Morris has been so impressed by parallel evolution, that he considers that humans would have evolved anyway, even if the dinosaurs had not been wiped out by the asteroid impact at the end of the Cretacious Period 64 million years ago. He also believes that this means that other, extraterrestrial alien races, would also be humanoid. The final chapter of one of his books describes an alien spacecraft landing in southern England. When the aliens leave their ship to make contact with us, they are a humans. So much so that when asked if they want food, not only do they say yes, but they also ask for water for their dog.

Conway-Morris’ views are extreme, and not shared by other biologists. And some researchers into extraterrestrial life, like Seth Shostak, believe that aliens would be radically different from us.

Even so, this piece of science news is fascinating, and makes you wonder about the other possibilities of similar species evolving parallel or iteratively.