1,000-year-old elephant bird eggshell helps crack case of how the extinct birds evolved

DNA obtained from ancient eggshells has provided a glimpse into the evolution of Madagascar’s extinct elephant birds.

The flightless birds are thought to have become extinct around 1,000 years ago, likely due to human activity on the island.

Elephant birds were the largest birds ever. Hence the name.

Some forms approached three metres and 500 kilograms. But individuals of the largest species are believed to have been able to grow to up to 860 kilograms. For comparison, the largest bird today, the ostrich, is a featherweight, reaching up to 2.8 metres in height, but weighing in at only 140 kg at most.

Eggshells examined by a team led by researchers from Western Australia’s Curtin University are from around the time the birds disappeared. The researchers found that genetic differences between the gigantic birds was linked to shell thickness, location and diet.

“The team collected more than 950 eggshell fragments from across Madagascar, says Dr Alicia Grealy, who is now based at the CSIRO. “Molecules preserved in some of these eggshells helped us discover a potentially new sub-species which lived in the top end of the country. We were also able to determine that different species ate a mixture of grass, shrubs and succulents.”

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Despite giant birds having existed for tens of millions of years (and, modern consensus is that the two-legged dinosaurs were birds as well), the team found that elephant birds evolved their monstrous proportions fairly recently.

Fragments of elephant bird eggshell lying on the beach in south-west Madagascar in 2014. Credit: James Haile.

“Another surprising finding is that the gigantic size of the largest elephant birds (Aepyornis maximus) likely arose within the last 1.4 million years, alongside the changing environment and ecosystem in Madagascar. This species nearly doubled in size over a very rapid and recent time frame,” Grealy explains.

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“It is amazing to think that these thousand-year-old egg fragments can give us insight as to where elephant birds lived, what they ate, how their ancestors might have looked, and how they evolved over the years,” Grealy says.

The research is published in Nature Communications.

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