On the island of Madagascar more than 1,200 years ago, flightless elephant
birds wandered free and deposited eggs as large as footballs. The University
of Colorado at Boulder (CU Boulder) and Curtin University in Australia have
discovered that the eggshell remains of these ancient creatures that
resembled ostriches contain important information about their time on
Earth.
The study, which was discovered without access to any skeletal remains and
was published on February 28 in the journal Nature Communications, describes
the discovery of a previously unidentified, distinct lineage of elephant
birds that roamed the wet, forested landscapes on the northeastern side of
Madagascar.
A new lineage of elephant birds has been discovered for the first time
solely from old eggshells, a ground-breaking accomplishment that will help
researchers understand the variety of birds that once roamed the globe and
why so many have since become extinct in the last 10,000 years.
"This opens up an area that nobody would have thought about before," said
Gifford Miller, a co-author of the study and distinguished professor of
geological sciences at the Institute of Arctic and Alpine Research (INSTAAR)
at the University of Colorado Boulder. Here may be another way to pose the
question, "Was there more avian variety than we are aware of?"
Madagascar, a tiny landmass like Africa, has been isolated from its
neighbors for at least 60 million years by deep ocean water. Lemurs,
elephant birds, and a wide variety of other creatures found nowhere else on
the world have all been created thanks to this geology, which has enabled
evolution to run amok. The largest of the elephant birds, Aepyornis, was a
feathered terror to behold for the Polynesian peoples who came here around
2,000 years ago. At more than 9 feet tall, weighing more than 1,500 pounds
each, and equipped with a pointy beak and lethal foot talons, it was
Madagascar's largest land animal.
It was unknown until recently where the birds fell into the phylogenetic
tree due to the scarcity of skeletal evidence and the fact that bone DNA
breaks rapidly in warm, humid environments. Scientists only knew that they
were genetic sisters to the New Zealand kiwi, the tiniest surviving ratite
in the world, and that they belonged to the family of flightless
ratites.
However, analysis of ancient eggshell DNA has provided more information
about the variety within the lineage in addition to confirming where the
elephant birds are located in this tree.
While fewer species were present in southern Madagascar at the time of
their extinction, main author Alicia Grealy, who performed this study for
her PhD thesis at Curtin University in Australia, also discovered new
diversity from the island's far north. "These results represent a
significant advancement in our knowledge of the intricate past of these
mysterious creatures. Surprisingly, there is a lot to learn about
eggshells.
An insignificant concept
One of the few experts who studies these pieces, Miller has spent more than
20 years examining eggshell remains in Australia and other parts of the
globe. In order to research the genetically enigmatic elephant avian, Miller
assembled a small crew in 2005 after receiving a $25,000 Easterbrook
Distinguished Scientist Award from the Geological Society of America.
In order to gather elephant bird eggshells from the island's dry southern
half, the crew first ventured out in 2006. Miller and Grealy's team focused
on the damp, wooded north of the island in an effort to better understand
the avian in a different environment, but when an independent researcher
used bone pieces to answer this evolutionary riddle before they could, they
shifted their attention elsewhere.
The crew surveyed areas where breezes had blown the sands away and revealed
ancient eggshells using high-resolution satellite images. The cracked pieces
are readily discernible to the unaided eye because there are no birds of any
comparable size presently residing on the island. The difficult task of
analyzing the ancient DNA started after the team traveled the island and
collected more than 960 ancient eggshell pieces from 291 places.
Skeletons may be "leaky" with their DNA because of their chemical
composition, which makes them less suitable for this kind of job. In
contrast, these thick eggshells' physical chemistry preserves their DNA like
it did the newborn avian that once developed inside of them and seals in
their organic matter for up to 10,000 years. This implies that it might be
challenging to separate for study.
Finding DNA segments that are lengthy enough to study is another challenge
because ancient DNA is frequently degraded. As a result, the researchers
assembled the shortened pieces in a manner akin to a "genetic jigsaw puzzle"
without realizing it would bring them to the identification of a novel
species of elephant bird.
"Science frequently develops in mysterious ways. According to Miller, head
of CU Boulder's Center for Geochemical Analysis of the Global Environment
(GAGE), "You don't always discover what you were searching for. Finding
something you weren't even seeking for is much more fascinating, too.
The embryo or the human?
Miller focuses on the "Quaternary," which is the most recent natural era in
Earth's past and the time when people first started to colonize the planet.
He claimed that big animals frequently went extinct when people arrived, but
experts are still unsure of the cause of the elephant bird's
extinction.
What is it about early people that is causing the extinction of big
creatures in particular? The debate has been ongoing for the entirety of
Miller's existence, who has a profession spanning five decades.
However, Miller and Grealy's groundbreaking work in the area of eggshell
DNA science may help us understand why large animals like the elephant bird
went extinct after the arrival of humans if geologists, archaeologists, and
biologists are able to collect and date more eggshell fragments from all
over the world.
You can actually answer some fascinating issues, Miller said, "with dozens
of little contributions from a whole bunch of individuals. "This could
provide a fresh perspective on the situation."
