By Evie Jordan
136 000 years ago, a small island in the Indian Ocean, off the south-east coast of Africa, almost completely disappeared below the waves causing the death of almost all animals living there, including the extinction of the Aldabra rail. What’s strange about this, is the fact that fossils of this flightless bird were found on that same island once it was above sea level again, 118 000 years ago. And yes, you read correctly. Not the near extinction of the birds, but a total wipe-out of that species. So what happened in 20 000 years?
When I first read about this in Science Daily I was shocked. The fact that a species had re-evolved in the same habitat it went extinct in is mind-boggling. This is all thanks to a process called iterative evolution.
Iterative evolution repeated evolution with the same, or similar structures in the development in the same mainline. Without the jargon, it means something that evolved in the same or similar way as it has done in the past. In theory, this would be quite common if the way it originally evolved was beneficial to the species but genetic mutations are random.
I find iterative evolution absolutely fascinating, from ammonites, sea cows, and sea turtles, to now, flightless birds, it’s all unquestionably captivating. The life and death of the Aldabra has led me to a new part of the study of evolution.
Mutations are not purposeful, but with the right conditions and the right amount of luck, mother nature might continue pulling off the near resurrection of species. Including that of the Aldabra rail.
Sources:
Julian P Hume, David Martill. Repeated evolution of flightlessness in Dryolimnas rails (Aves: Rallidae) after extinction and recolonization on Aldabra. Zoological Journal of the Linnean Society, 2019; DOI: 10.1093/zoolinnean/zlz018
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