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 Scientists on Thursday identified the closest relative of New
Zealand's famed kiwi, a shy chicken-sized flightless bird, as the
elephant bird of Madagascar, a flightless giant that was 10 feet (3
meters) tall and went extinct a few centuries ago.
The surprising findings, based on DNA extracted from the bones of
two elephant bird species, force a re-evaluation of the ancestry of
the group of flightless birds called ratites that reside in the
world's southern continents, they added.
The group, which boasts some of the world's largest birds, includes
emus and cassowaries in Australia, rheas in South America, ostriches
in Africa and kiwis in New Zealand. Ratites that have disappeared in
recent centuries include the moa of New Zealand and the elephant
bird.
The researchers compared elephant bird DNA to the other birds and
saw a close genetic link to the kiwi despite obvious differences in
size, body shape and lifestyle - and the fact they lived about 7,000
miles (11,500 km) apart.
The largest elephant bird species weighed more than 600 pounds (275
kg). Kiwis reach around 11 pounds (5 kg).
There has been a lively debate among bird experts about the origins
of the ratites and how they came to live where they do.
The world's first birds arose about 150 million years ago. Over the
eons, some species lost the ability to fly but became large and
formidable.
Many scientists have thought the ancestors of today's ratites were
already flightless when they were isolated in their current
locations by the separation and drift of the southern continents
over the past 130 million years.
The new findings indicate the continents had already separated
before ratite ancestors showed up, meaning the forebears of these
flightless birds reached their current homes by flying.
"It does seem a little ironic, but in fact it's the simplest
explanation for the facts we observe," said Kieren Mitchell of the
University of Adelaide's Australian Centre for Ancient DNA.
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Alan Cooper of University of Adelaide said the new data suggest that
flying ratite ancestors dispersed around the world right after the
mass extinction killed the dinosaurs 65 million years ago and before
mammals became dominant.
Mitchell said the researchers had expected to find that the elephant
bird and ostrich were the most ancient lineages of ratite because
Africa and Madagascar were the first landmasses to separate from
what had been an ancient super-continent.
Instead, they found that elephant birds and kiwis arose from a
common ancestor around 50 million years ago after even New Zealand
had become isolated. Previous research had suggested Australia's
ratites as the kiwi's closest relatives.
"If the common ancestor of kiwi and elephant birds lived on
Madagascar, then kiwis must have flown to New Zealand. If this
ancestor lived on New Zealand, then elephant birds must have flown
to Madagascar," Mitchell said. "Or perhaps the common ancestor of
both elephant birds and kiwis flew to their final locations from
somewhere else entirely."
The study was published in the journal Science.
(Reporting by Will Dunham; Editing by James Dalgleish)
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