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More than 1,200 years ago, flightless elephants roamed the island of Madagascar and laid eggs larger than footballs. While these ostrich-like giants are now extinct, new research from the University of Colorado at Boulder and Curtin University in Australia reveals that their eggshell remains hold valuable clues to their time on Earth.
Posted last week in Nature Communication, the study describes the discovery of a separate, previously unknown lineage of elephant birds that roamed the moist, forested landscapes of northeastern Madagascar – a discovery made without access to any skeletal remains.
It is the first time that a new line of elephant birds has been identified from ancient eggshells, a pioneering achievement that will allow scientists to learn more about the diversity of birds that once roamed the world and why so many of them have since disappeared in the past. 10,000 years old.
“This is the first time that a taxonomic identification has been derived from a bird elephant eggshell and it opens up a field that no one would have thought of before,” said the co-author of the article, Gifford Miller, eminent professor of geological sciences and member of the faculty of the university. Institute of Arctic and Alpine Research (INSTAAR) at CU Boulder. “Here’s maybe another way to look into the past and ask, ‘Was there more diversity in birds than we think?'”
What a freshly laid whole Aepyornis egg would have looked like, seen in a market near the town of Toliara on the southwest coast of Madagascar. Photo by Gifford Miller
The largest elephant birds were over 9 feet tall
Like a small continent, Madagascar has been separated from Africa and neighboring continents by deep ocean waters for at least 60 million years. This geology has allowed evolution to run wild, producing lemurs, elephant birds, and all manner of animals that exist nowhere else on the planet. For the Polynesian people who arrived here about 2,000 years ago, the largest of the elephant birds, Aepyorniswas a feathery terror to behold: at over 9 feet tall, weighing over 1,500 pounds each, and equipped with a sharp beak and deadly claws, it was Madagascar’s largest land animal.
Due to limited skeletal remains – and the fact that bone DNA degrades rapidly in warm, humid areas – it was unclear until recently where birds fit on the evolutionary tree. Most scientists knew they were part of the flightless ratite family, a genetic sister to the New Zealand kiwifruit, the world’s smallest living ratite.
Ancient eggshell DNA, however, not only confirmed where the elephant birds are found in this tree, but revealed more about the diversity within the lineage.
“Although we found that there were fewer species living in southern Madagascar at the time of their extinction, we also discovered new diversity in the far north of Madagascar,” said lead author Alicia. Grealy, who conducted this research for his doctoral dissertation at Curtin University in Australia. . “These findings are an important step forward in understanding the complex history of these enigmatic birds. There is surprisingly much to discover from the eggshell.
An eggshell idea
Miller has analyzed eggshell remains in Australia and around the world for more than 20 years – one of the few scientists to study these fragments. So in 2005, when he received $25,000 as part of the Geological Society of America’s Easterbrook Distinguished Scientist Award, Miller assembled a small team to study the evolutionary elephant.
The team originally set out in 2006 to collect eggshells from elephant birds in the dry southern half of the island. When an unaffiliated researcher used bone fragments to solve this evolutionary mystery before they could, Miller and Grealy’s team turned their attention to the wet and forested northern half of the island, in hope to better understand the bird in a different biome.
Using high-resolution satellite imagery, the team spotted places where winds had blown sand away and exposed ancient eggshells. No birds of a similar size currently live on the island, so the cracked pieces are easily recognizable with the naked eye. After the team traversed the island and collected over 960 ancient eggshell fragments from 291 locations, the hard work began: analyzing the ancient DNA.
Due to their chemical makeup, Skeletons can be “leaky” with their DNA, making them less ideal for this type of work. By comparison, the physical chemistry of those thick eggshells locks in its organic matter for up to 10,000 years and protects its DNA just as it did the baby bird that grew up inside. This means that it can be quite difficult to extract for analysis.
Another problem is finding long enough strands of DNA to analyze, as old DNA is often degraded. As a result, scientists pieced together the shortest fragments into a kind of “genetic puzzle” – with no idea that this would lead them to discover a new type of elephant bird.
“Science often advances in obscure ways. You don’t always find what you’re looking for,” said Miller, director of the Center for Geochemical Analysis of the Global Environment (GAGE) at CU Boulder. “And it’s much more interesting to find what you didn’t know you were looking for.”
The human or the egg?
Miller studies the “Quaternary,” the most recent geological period in Earth’s history and when humans first appeared on the landscape. When humans appeared, he said, large animals often disappeared, but scientists still don’t know why the elephant bird was one of them.
“What did early humans do that led to the extinction of large animals, in particular? It’s been a lifelong debate,” said Miller, whose career now spans five decades.
If geologists, archaeologists and biologists are able to collect and date more eggshell fragments from around the world, the pioneering work of Miller and Grealy in the field of eggshell DNA science eggs could shed light on why large animals like the elephant bird became extinct. disappeared after the arrival of the man.
“With a lot of small contributions from a whole bunch of people, you can actually solve interesting questions,” Miller said. “It could open up a new way of looking at things.”
Thanks to the University of Colorado at Boulder for providing this news.
