A Theory on How Flightless Birds Spread Across the World: They Flew There

Ellie Briskin                                                                         Earth Science C Even

May 23, 2013                                                                         Current Event #2

A Theory on How Flightless Birds Spread Across the World: They Flew There

Zimmer, Carl. "A Theory on How Flightless Birds Spread Across the World: They Flew There." The New York Times. The New York Times, 22 May 2014. Web. 22 May 2014. <http://www.nytimes.com/2014/05/23/science/a-theory-on-how-flightless-birds-spread-across-the-world-they-flew-there.html?ref=science&_r=0>

Lately, scientists have been looking for clues about the ancient elephant bird, a creature known to roam around Madagascar but that went extinct a few hundred years ago, possibly even in the 1800s. This bird, the heaviest bird known to science weighing in at as much as 600 pounds, was also flightless, and had useless, shriveled arms instead of proper wings. Although scientists have been interested in this bird for decades, they have only just been able to extract DNA from its fossils, giving researchers hoards more information than they had before. After analyzing this DNA, they were shocked to find that the closest relative of the elephant bird is the kiwi, a six-pound flightless bird native to New Zealand, over 7,000 miles away from Madagascar.

My initial reaction was to notice just the size difference, but I soon realized that aspect was insignificant, for the issue now became much larger than these two species. What really had scientists at the edge of their seats was the fact that these two birds, so closely related, totally contradicted the current theory of evolution. They began considering other flightless birds of the same family, the family of ratites, from ostriches in Africa to emus in Australia. These birds are distinguished both by their lack of flight and the unique bone structure in their heads, and also include the cassowaries of Australia and New Guinea, the rheas of South America, and the extinct moa of New Zealand.

The question of how these ratites ended up all over the southern hemisphere was thought to be answered by continental drift. This theory states that 200 million years ago, all of the southern landmasses were part of the supercontinent Gondwanaland, and as the pieces (continents) drifted away, they carried their species with it, and these species eventually evolved independently. The only issue with this theory is that the elephant bird and kiwi are thought to have evolved from the same bird around 50 million years ago, 150 millions of years after the breakup of Gondwanaland. Not only that, but scientists think that the closest relative of the moa, another ratite, is a small flying bird from Central and South America called the tinamou. How could the tinamou fly and moa not, if their common ancestor, the same common ancestor for all ratites, is thought to have been wingless?

Considering there’s no other way to get across the ocean from Madagascar to New Zealand without flying, some experts think that’s exactly what the ancestor of these now-flightless birds did. A new hypothesis has been proposed which suggests that the common ancestor of ratites was actually a partridge-like bird that could travel by air. According to this hypothesis, the bird supposedly flew across much of the southern hemisphere and then evolved independently, rather than evolving soon after the split of Gondwanaland. While this explanation works, there is still little evidence supporting it, leading many scientists to be skeptical. But what all scientists agree on is that the history of the elephant birds has sparked as many questions as it answered, and that it won’t be long until the full story of the ratites, both living and extinct, is told.

The relevance that elephant birds has on society is not obvious, but definitely present. While they might not have monumental effects on everyone’s daily lives, the study of the study of these birds directly relate to what our class, and classes around the world, have studied in Earth Science. We recently covered the topic of plate tectonics, which included the theory of continental drift, which was part of my summary. One of the pieces of evidence for Continental Drift was that certain plant and animal species were found on corresponding parts of South America, Africa, and Australia, proving that the continents used to be conjoined. Given the timeline of ratite evolution these birds don’t fit with this theory, but it was interesting to see an exception to what I thought was a theory that covered all species. Not only that, but any new information on evolution can give scientists clues into how our current human race may evolve in the future, which I find extremely captivating. 

I was extremely impressed by how well this article was written. Most other scientific articles that I’ve read recently jumped around from subtopic to subtopic so frequently that I couldn’t follow I was reading, but I had no problems with that in this article. It was also strongly written, as the writer backed up all of his claims with clear evidence.

Still, the article wasn’t flawless. I found it so easy to read and understand, in fact, that it may have even been too simple; a little more complex vocabulary and detailed explanation of terms would have been welcome. Not only that, but the pictures also weren’t very assistive. The picture of the kiwi bird helped me visualize the creature in comparison to the massive elephant bird, but wasn’t of much use other than that. It would have been nice to see a map instead, labeling the location of the different ratites and arrows from their common ancestors, as this article is more about evolutionary patterns than it is just kiwi birds. Overall, I really enjoyed this article and felt like I had actually learned something after reading it, and plan on looking into other articles by the same author.