(CN) — Long before humans domesticated chickens, they had tamed the much larger and dangerous cassowary bird, according to new research released Monday.
"This behavior that we are seeing is coming thousands of years before domestication of the chicken," said Kristina Douglass, assistant professor of anthropology and African studies at Penn State, in a statement. "And this is not some small fowl, it is a huge, ornery, flightless bird that can eviscerate you. Most likely the dwarf variety that weighs 20 kilos (44 pounds)."
In the study published in the journal Proceedings of the National Academy of Sciences, an international research team estimates humans in New Guinea domesticated the birds starting around 18,000 years ago. The scientists relied on ancient cassowary eggshells to estimate the developmental stage of the embryos when the eggs were cracked open.
“The data presented here may represent the earliest indication of human management of the breeding of an avian taxon anywhere in the world, preceding the early domestication of chicken and geese by several millennia," the study states.
The researchers said cassowaries “bear more resemblance to velociraptors than most domesticated birds.”
"However, cassowary chicks imprint readily to humans and are easy to maintain and raise up to adult size," the study states.
Imprinting is the process by which a newly hatched bird creates a connection to the first creature or object it sees, believing it to be its mother.
To determine whether our human ancestors were raising the birds or just eating them, scientists gathered clues from ancient eggshells.
"I've worked on eggshells from archaeological sites for many years," Douglass said. "I discovered research on turkey eggshells that showed changes in the eggshells over the course of development that were an indication of age. I decided this would be a useful approach."
To determine the age at which cassowaries hatched, the researchers first examined modern ostrich eggs. They recorded the changes occurring to the eggshells during incubation, allowing the scientists to gain insight as to when these changes typically happened.
“The insides of the eggshells change through development because the developing chicks get calcium from the eggshell. Pits begin to appear in the middle of development,” the researchers said.
"It is time dependent, but a little more complicated," said Douglass. "We used a combination of 3D imaging, modeling and morphological descriptions."
Using the information they gleaned from the development of ostrich eggs, the research team applied that knowledge to ancient cassowary eggs.
"What we found was that a large majority of the eggshells were harvested during late stages," said Douglass. "The eggshells look very late; the pattern is not random. They were either into eating baluts or they are hatching chicks."
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