Evolution Brings Extinct Bird Back to Life! Except it Didn’t

A news story has been circulating a fair bit in the past couple of weeks. This story has been picked up by numerous news and science outlets. How it is being reported and explained is just plain misleading and inaccurate.

The Aldabra Rail is a subspecies of the White-throated Rail.

Here are a few titles that show how the subject is being covered.

Science Magazine – Evolution Brings Extinct Island Bird Back into Existence

Smithsonian Magazine – How Evolution Brought a Flightless Bird Back from Extinction

CBS News – An Extinct Bird Species Has Evolved Back into Existence, Study Says

From these titles, and from the bodies of the articles themselves, readers would think that the same species of bird existed at some point in the past, went extinct (as in died out completely), and then re-evolved!

That does not happen.

Here is what actually did occur.

The small atoll of Aldabra is a pretty spectacular spot. It is very remote. It is quite beautiful. It is home to a bunch of unique animals found no where else on earth. It has one of the longest fossil records on any island in the Indian Ocean.

That fossil record includes a lot of the animals that have called the atoll home over the past few million years. One of those animals was the Aldabra Rail. This rail was a small flightless bird that was probably found hunting through reed beds along the edges of water. The Aldabra Rail went extinct about 136,000 years ago at about the same time that global sea level was rising and submerging oceanic islands like Aldabra. After a few thousand years, sea level dropped and Aldabra became an exposed island once more. Not long after that fossils of a rail on Aldabra start showing up again.

There are a couple of possible explanations. One is that some remnant population of the Aldabra Rail hung on, some how, and did not die. These were flightless birds, so it is not clear how this might have happened, but perhaps a small population managed to survive on a floating raft of vegetation long enough to reach an exposed bit of land. This seems like a very long shot. It is much more likely that the Aldabra Rail simply died out completely. It went extinct.

The other possible explanation is much more likely and widely understood and accepted, and it is this: the Aldabra Rail went extinct when the atoll went under water. Then after it re-emerged, a group of birds likely from the same parent stock of the original Aldabra Rail re-colonized the atoll (quite probably from Madagascar). This new group of colonizers eventually became flightless and filled the same, or very similar, ecological niche as the original Aldabra Rail.

This is a process called iterative evolution and it is pretty rare. The definition of iterative evolution is: the evolution of similar or parallel structures in the development of the same main line.

But iterative evolution does not produce the same species twice. It may produce similar species, but to produce the same species twice would require starting with the same gene pool twice. The group of birds that first colonized Aldabra, and became the Aldabra Rail 1.0, had a unique combination of genes to work with. The group of birds that later colonized Aldabra, and became the Aldabra Rail 2.0, had a unique combination of genes to work with. Those two combinations of genes may have been similar, but they were not the same. Therefore the decedents of those two groups would not be the same.

I really think that the implications of how this story is being reported is really misleading and possible even damaging.

Misleading because they imply that a species can evolve twice. To go back to the definition of  iterative evolution, it the evolution of “similar or parallel structures…” Similar or parallel structures are not the same as identical species. Two rails that evolved at different times in the same place and that are both flightless, are not the same species.

Damaging because there is weight to the idea of extinction. Extinction is forever. It means that an entire evolutionary lineage has ended, and any potential future that that lineage may have had is gone. If the idea of extinction becomes an impermanent one, it looses its urgency and tragedy. People may well not worry about extinction as that species can just re-evolve. No harm, no foul.

Again, no species can ever occur twice. Once a species goes extinct, that is it for that evolutionary lineage. Even if some other lineage emerges that is close, it will not be the same and will not have the same evolutionary trajectory or potential.

When reporting on science, I feel strongly that the ideas behind the science should be accurately represented. I think it is especially distressing when the sources of the misrepresentations are otherwise reputable sources for science.

I hope the current Aldabra Rail has a long future filled with descendants, and I mourn the loss of the previous rail of Aldabra and the lineage it might have left behind, but never will.

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Dinosaur Feathers

Single feather, and a mite, preserved in Late Cretaceous amber found in Canada.

In the movie, Jurassic Park, humans are able to get dinosaur DNA from insects that were preserved in fossilized amber millions of years ago. Well, it has been very convincingly shown that any DNA that might get trapped in amber during the age of dinosaurs would degrade too badly over time to still be viable today. However, this does not mean that amber is useless in preserving amazing structures that we can find and learn from and marvel at.

A recent report that appeared in the journal Science is an excellent example of what I mean. Researchers examined a number of fossilized feathers that were preserved in amber during the Late Cretaceous. These feathers likely came from dinosaurs! And they are beautiful, having been spectacularly preserved in the amber that surrounds them. At this point, no one is exactly sure if these some of these feathers came from early members of what would become the bird lineage, or if they came from non-avian dinosaurs, but either way, the feathers are stunning. In fact, the feathers are in such high quality condition that even tiny features can be observed. Impressively, many of these tiny features on the dinosaur feathers look exactly like the tiny features one would see on the feathers of a modern bird. One example of this is the way that the barbs of some of the feathers twist like a corkscrew. This is a feature also found in modern water birds and may suggest that the dinosaur that those feathers came from lived in close association with water as well. The researchers can even take a stab at figuring out what color some the feathers were; colors that range from white to brown to black. This backs up a lot of other research that has suggested that dinosaur feathers probably had a wide range of colors and patterns, some of them quite bright and dramatic!

A feather found in Late Cretaceous Canadian amber. The dark masses all along the filaments are regions of pigment concentration. This feather was probably medium to dark brown.

Another exciting outcome of all these fossils is that they represent a range of stages in feather evolution. Some of the fossils are little more than very thin filaments, sometimes referred to as protofeathers (or dino fuzz). These protofeathers are probably some of the earlier stages in the evolution of the structures that would eventually become the tail feather of a Peacock or the crest feather of a Royal Flycatcher. These filaments have been found preserved in the rock surrounding other non-avian dinosaur fossils, but they have never been seen in such detail as they can be in the amber. Others of these fossil feathers show much more elaborate feathers that have many of the same complex features of modern feathers.

Follow this link: http://io9.com/5840854/dinosaur-feathers-discovered-in-canadian-amber to see more photos of feathers fossilized in amber. And next time you see a member of the only living lineage of dinosaurs (a.k.a. a bird), take a moment to think about the feathers that cover its body and to realize that millions of years ago, there were animals sporting feathers that look just about the same. Pretty amazing!

A cluster of 16 feathers preserved in Canadian Late Cretaceous amber.

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