With the help of ancient bird DNA, a 150-year-old flight mystery of evolution has finally been solved. The kiwi, an iconic bird of New Zealand, did once have the power of flight. Though thought to be a close relative of the emu, in actuality, the tiny kiwi is more closely related to a bird that has been extinct since the 17th century, the Madagascan elephant bird. This giant stood 10 feet tall and weighed almost 500 pounds. A study done at the Australian Center for Ancient DNA (ACAD) at University of Adelaide also found that both the emu and elephant bird had the ability to fly before becoming grounded.
Dr. Trevor Worthy of Flinders University, also in Australia, noted that fossils of small ancestors of the modern day kiwi have been found recently. From what the scientists observed, they suspected that previous kiwis may have been able to fly. Genetic tests done on the fossils supported the interpretation. When they arrived in New Zealand, kiwis were flying birds. Dr. Worthy went on to explain that this theory also provided a reason for the kiwi having remained so diminutive. Large herbivores, like the moa, were already in New Zealand. Therefore, the kiwi stayed small and became nocturnal and insectivorous.
ACAD’s new study has also managed to solve other mysteries surrounding the ratite birds, which are flightless giants, like the ostrich and emu. Found across the continents of the southern hemisphere, ratites are some of the world’s biggest birds. The largest of the nine known species of moa, now extinct, stood 12 feet tall and weighed over 500 pounds. The various species were generally thought to have formed due to the inevitable isolation of flightless birds after the separation of the southern hemisphere continents through the passed 130 million years.
Instead, with the help of ancient DNA from two elephant bird bones at the Museum of New Zealand, researchers with ACAD found the close genetic relation with kiwis. Regardless of the differences in ecology, geography and morphology, the two birds are indeed related. Kieren Mitchell, a researcher at ACAD said that the result was a big surprise for them. Because Madagascar and New Zealand were only physically joined when Antarctica and Australia were, the result confirms that the ratites could only have dispersed themselves by flying.
These results have now corrected previous conclusions made by Professor Alan Cooper, ACAD director, in the 1990s. His findings showed that the kiwi was more closely related to the cassowary and emu.
Not only has the ancient elephant bird DNA helped solve the flight mystery, it also gave the researchers the ability to estimate when ratites separated from one another. Professor Cooper said that their best guess is that the ratites dispersed sometime between the extinction of the dinosaurs and the dramatic increase in mammal sizes, making them the group of dominance on the globe. The theory goes on to explain that the ratites could have exploited that limited window of opportunity to evolve into large herbivores. Once the mammals also got bigger, approximately 50 million years ago, the window was closed, unless the birds were on an island that was free of mammals, like the Dodo.
By Stacy Lamy