"It is time dependent, but a little more complicated," said Douglass. "We used a combination of 3D imaging, modeling and morphological descriptions."
The researchers then turned to legacy shell collections from two sites in New Guinea — Yuku and Kiowa. They applied their approach to more than 1,000 fragments of these 18,000- to 6,000-year-old 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."
A balut is a nearly developed embryo chick usually boiled and eaten as street food in parts of Asia.
The original archaeologists found no indication of penning for the cassowaries. The few cassowary bones found at sites are only those of the meaty portions — leg and thigh — suggesting these were hunted birds, processed in the wild and only the meatiest parts got hauled home.
"We also looked at burning on the eggshells," said Douglass. "There are enough samples of late stage eggshells that do not show burning that we can say they were hatching and not eating them."
To successfully hatch and raise cassowary chicks, the people would need to know where the nests were, know when the eggs were laid and remove them from the nest just before hatching. Back in the late Pleistocene, according to Douglass, humans were purposefully collecting these eggs and this study suggests people were not just harvesting eggs to eat the contents.
Also working on this project from Penn State were Priyangi Bulathsinhala, assistant teaching professor of statistics; Tim Tighe, assistant research professor, Materials Research Institute; and Andrew L. Mack, grants and contract coordinator, Penn State Altoona.
Others working on the project include Dylan Gaffney, graduate student, University of Cambridge, U.K.; Theresa J. Feo, senior science officer, California Council of Science and Technology; and Megan Spitzer, research assistant; Scott Whittaker, manager, scientific imaging; Helen James, research zoologist and curator of birds; and Torben Rick, curator of North American Archaeology, all at the Natural Museum of Natural History, Smithsonian Institution. Glenn R. Summerhayes, professor of archaeology, University of Otago, New Zealand; and Zanell Brand, production scientist, Oudtshoorn Research Farm, Elsenburg, Department of Agriculture, Western Cape Government, South Africa, also worked on the project.
The Smithsonian National Museum of Natural History, the National Science Foundation and Penn State's College of the Liberal Arts supported this work.