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(CNN)The earliest bird reared by humans may have been a cassowary -- often called the world's most dangerous bird because of its long, dagger-like toe.
Territorial, aggressive and often compared to a dinosaur in looks, the bird is a surprising candidate for domestication.
However, a new study of more than 1,000 fossilized eggshell fragments, excavated from two rock shelters used by hunter-gatherers in New Guinea, has suggested early humans may have collected the eggs of the large flightless bird before they hatched and then raised the chicks to adulthood. New Guinea is a large island north of Australia. The eastern half of the island is Papua New Guinea, while the western half forms part of Indonesia.
"This behavior that we are seeing is coming thousands of years before domestication of the chicken," said lead study author Kristina Douglass, an assistant professor of anthropology and African studies at Penn State University.
"And this is not some small fowl, it is a huge, ornery, flightless bird that can eviscerate you," she said in a news statement.
The researchers said that while a cassowary can be aggressive (a man in Florida was killed by one in 2019), it "imprints" easily -- it becomes attached to the first thing it sees after hatching. This means it's easy to maintain and raise up to adult size.
Today, the cassowary is New Guinea's largest vertebrate, and its feathers and bones are prized materials for making bodily adornments and ceremonial wear. The bird's meat is considered a delicacy in New Guinea.
There are three species of cassowary, and they are native to parts of northern Queensland, Australia, and New Guinea. Douglass thought our ancient ancestors most likely reared the smallest species, the dwarf cassowary, that weighs around 20 kilograms (44 pounds).
The fossilized eggshells were carbon-dated as part of the study, and their ages ranged from 18,000 to 6,000 years old.
Humans are believed to have first domesticated chickens no earlier than 9,500 years ago.
Not for snacking
To reach their conclusions, the researchers first studied the eggshells of living birds, including turkeys, emus and ostriches.
The insides of the eggshells change as the developing chicks get calcium from the eggshell. Using high-resolution 3D images and inspecting the inside of the eggs, the researchers were able to build a model of what the eggs looked like during different stages of incubation.