Long before chicken domestication, humans appear to have raised a different bird species – one capable of ripping a person apart with a single raking kick. Cassowaries make birds’ status as the surviving dinosaurs easy to believe, yet according to a new study, these are the beasts humans somehow chose to raise to adulthood. Strange as that decision may seem, it could explain the cassowary’s survival and the fate of New Guinea’s rainforests.
Eggshells deposited at Yuku and Kiowa in the New Guinea Highlands disproportionately appear to have been collected just a few days before they hatched. In Proceedings of the National Academy of Sciences, the team who discovered this pattern explains it (almost in time for world Cassowary Day) as the result of people's aim to raise the hatchlings, not cook the eggs.
The heaviest birds to have inhabited the Earth in recent times – New Zealands’ Moa and Madagascar’s elephant bird – both quickly became extinct shortly after humans arrived on their home islands. Somehow, however, three species of cassowary have survived in New Guinea and Australia, co-inhabiting with humans for tens of thousands of years.
It’s just possible cassowaries’ survival is a result of humans choosing to raise the young to adulthood as the best way to get their meat, rather than hunting wild birds alone. If so, it proved a very beneficial choice for the health of the rainforests in which cassowaries live, allowing them to continue their vital role as spreaders of seeds.
The shape and color of cassowary eggs changes as they get close to hatching and the embryos absorb calcium from the shells. Dr Kristina Douglass of Penn State University and co-authors used this fact to study the developmental stages of shells deposited at the two sites 18,000 years ago.
They also noted that while some shells showed signs of having been cooked; "There are enough samples of late stage eggshells that do not show burning that we can say they were hatching and not eating them,” Douglass said in a statement.
Cassowaries live on fruit rather than meat, but their lethal claws still make them major threats to anything they don’t like – humans included. Douglass suspects the dwarf cassowary variety Casuarius bennetti were the ones being raised, rather than the two larger species. Nevertheless, she noted; “This is not some small fowl, it is a huge, ornery, flightless bird that can eviscerate you.”
There are unconfirmed signs of humans forming a symbiosis with rock doves at Gibraltar 67 thousand years ago, but that aside, the work presented here represents the oldest evidence bird farming in human history. "This behavior that we are seeing is coming thousands of years before domestication of the chicken," Douglass said.
Cassowary nests are rare and hard to find. Moreover, the father guards and incubates them until hatching. It would have taken considerable skill to identify the right time to harvest the eggs, and killing the male to get to them would have carried risks. Nevertheless, New Guineans continue to raise cassowaries today, taking advantage of the fact they imprint easily on humans if one is the first to feed them after hatching.