IT'S CALIFORNIA'S archaeological equivalent of the dodo bird, and the fate of this all-but-forgotten flightless duck that disappeared 2,500 years ago is reviving debate over the theory that prehistoric hunters drove to extinction woolly mammoths and other large creatures that once roamed the North American continent, according to a new study.
The legacy of this land-bound bird also serves to remind modern humans how best to protect imperiled species still in our midst, added Brian Codding, an archaeology Ph.D. student at Stanford University who contributed to the study published Wednesday in the Proceedings of the National Academy of Sciences.
The study describes solid evidence that prehistoric people, like their modern counterparts, pushed other species over the brink. said Terry Jones, the lead author and an anthropologist with California Polytechnic State University.
"We have the best archaeological record for a human-caused extinction in North America," Jones said.
The birds, about the size of geese, were masterful underwater swimmers but had stumps for wings and couldn't fly. It's called Chendytes, and fossilized bones of the flightless duck found in 14 ancient middens that dot the Pacific coast between Southern California and southern Oregon show that humans began hunting the bird nearly 12,000 years ago.
Because Chendytes couldn't flee by air, it nested on rocky outcroppings, offshore rocks and coastal islands, where it was safe from predators.
But when indigenous Californians began building seaworthy vessels about 12,000 years ago, they soon followed the bird to its nesting grounds, easily capturing it and its eggs, Jones explained.
"They could have just grabbed them, because they're flightless," Jones said. "They were the epitome of sitting ducks."
Flightless birds rarely fare well in the face of human encounters. On the Indian Ocean island of Mauritius, the last of the flightless dodo birds died about a century after sailors first arrived in 1561.
Chendytes was a meaty species, yielding large drumsticks that undoubtedly appealed to the natives, according to the California State Parks Web site, describing a 5,700-year-old midden north of Santa Cruz that held a large collection of Chendytes bones.
Indigenous Californians would toss Chendytes remains into middens — the equivalent of trash heaps. Along with Chendytes bones, archaeologists have found remains of other meals, such as shells of mussels, barnacles,abalone and rock oysters.
The same middens were used for thousands of years by native populations, and those that remain provide an invaluable archaeological record of daily life for the state's first inhabitants.
All of the middens studied had Chendytes bones, including the oldest of the group, an 11,000-year-old debris pile in the Channel Islands. Remnants of the flightless bird were found in its lowest layer, showing native inhabitants hunted the bird as far back as the record reveals.
Jones, along with other colleagues, tracked the steady decline of Chendytes bones in the middens, however, until they no longer appeared about 2,500 years ago, according to recent radiocarbon dating Jones and others conducted.
Their radiocarbon dating work also moved the estimated extinction date of the flightless duck up 1,300 years over previous estimates, Jones noted.
That's significant, he explained, because the midden record shows that the vulnerable Chendytes, which was virtually helpless against hunters and the dogs that sometimes accompanied them, co-existed with humans for at least 8,000 years before an expanding native population finally pushed the duck over the abyss into extinction.
Overkill theory
A prevailing hypothesis among paleontologists, which has trickled down into common knowledge, holds that ancient hunters rapidly killed off many animal species in North America.
It's called the "Pleistocene overkill" hypothesis, and it holds that shortly after ancient hunters arrived in North America about 13,000 years ago, they engaged in a "prehistoric blitzkrieg" that drove to extinction in less than 1,000 years at least 35 species of animals, including the mastodon, woolly mammoth, an ancient beaver the size of a black bear and a giant sloth as tall as a giraffe, as well as smaller herbivores.
But since the easily captured Chendytes persisted for at least 8,000 years before succumbing to overhunting, that raises serious doubts for Jones and others as to whether prehistoric humans had the wherewithal to bring down any species in a thousand years or less.
This new study on Chendytes, the most comprehensive yet on the flightless bird, "suggests that to wipe out a species, it would have to take some time," Jones said.
While that may sound like a fine point to those dismayed at humanity's seemingly hard-wired proclivity to wantonly exploit other species until they reach their demise, the conclusion of the study points to the crucial role of climate change in ushering in the extinction of these species, Jones said.
"I'm fairly certain that climate-change events provide a better explanation for what we see," he said.
Heat stress suspected
The extinction of many of these species coincided with the ending of an ice age and the warming of global temperatures that could have led to heat stress, alterations in plant communities and other changes threatening the ability of these animals to survive.
The overkill hypothesis is far from settled, however.
Paul Koch, a paleontologist at the University of California, Santa Cruz, thinks the gradual decline of Chendytes over 8,000 years shows that either the California natives were managing their hunting to keep the population viable, or that there weren't enough human inhabitants during most of that period to threaten the birds' existence.
Koch also thinks its island habitat made it harder to catch, but Jones believes the ocean was little deterrent to the seafaring natives.
What is clear from the history of Chendytes is that desirable prey that can't outsmart hunters face bleak long-term prospects, Koch said.
"If there are enough people, and the bird is pretty easy to get, and it's tasty, then it will likely go extinct," Koch said.
But the fate of Chendytes provides a critical guide for modern humans willing to control their interactions with other species, added Codding, the Stanford Ph.D. student.
"The Chendytes case," Codding said, "highlights the importance of protecting breeding grounds of particularly vulnerable species, especially from human exploitation."
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