viernes, 25 de febrero de 2011
Discovery of Oldest Northern North American Human Remains Provides New Insights Into Ice-Age Culture
Scientists have discovered the cremated skeleton of a Paleoindian child in the remains of an 11,500-year-old house in central Alaska. The findings reveal a slice of domestic life that has been missing from the record of the region's early people, who were among the first
The discovery, by Ben Potter of the University of Alaska Fairbanks and colleagues, appears in the 25 February issue of the journal Science.
"The site is truly spectacular in all senses of the word," Potter said. "The cremation is quite significant, but the context of the find is important too."
In contrast to the temporary hunting camps and other specialized work sites that have produced much of the evidence of North America's early habitation, the newly discovered house appears to have been a seasonal home, used during the summer. Its inhabitants, who included women and children, foraged for fish, birds and small mammals nearby, according to Potter's team.
"Before this find we knew people were hunting large game like bison or elk with sophisticated weapons, but most of sites we had to study were hunting camps. But here we know there were young children and females. So, this is a whole piece of the settlement system that we had virtually no record of," he said.
"As part of the Beringian Land Bridge, Alaska was an important crossroads for the Old and the New Worlds. This study makes an important contribution to our understanding of the early inhabitants of Beringia and their culture," said Brooks Hanson, Deputy Editor, Physical Sciences, at Science.
The young child probably died -- it's not clear how -- before being cremated in a large pit in the center of the home. This pit had many purposes, including cooking and waste disposal. After the cremation, the pit was sealed up and the house was abandoned, the researchers report.
The name of the site where this discovery took place, "Upper Sun River," is a translation of a nearby Athabaskan placename, Xaasaa Na'. The site lies within a dune field in the boreal forest of the Tanana lowlands. The child has been named Xaasaa Cheege Ts'eniin (or Upward Sun River Mouth Child) by the local Native community, the Healy Lake Tribe.
The house's floor was dug about 27 centimeters below the original ground surface. Colored stains in the sediment suggest that poles may have been used to support the walls or roof, though it's not clear what the latter would have been made of. The entire house has not yet been fully excavated, so its total size is still unknown.
The pit at the center was oval-shaped and about 45 centimeters deep. In sediment layers beneath the skeleton, the researchers found bones of salmon, ground squirrels, ptarmigan and other small animals. The skeleton was a particular surprise, since no human remains older than a few hundred years have ever been found in Subarctic Alaska.
Only about 20 percent of the burned skeleton was preserved. The remains don't reveal the child's sex, but they do include teeth, which allowed the researchers to conclude the child was around three years old. The remains showed no signs of injury or illness, though that isn't surprising, since most health problems don't leave traces in bones.
Potter's team didn't find any objects that were clearly grave goods. The researchers did excavate two pieces of red ochre along with the skeleton, but their significance is unclear. While red ochre has been part of burials around the world, it also has many other uses.
This lack of symbolic objects is typical for a mobile hunter-gatherer society like the one at Upper Sun River, according to Potter. It should not be interpreted as a sign that the child's death was treated casually, Potter said.
"All the evidence indicates that they went through some effort. The burial was within the house. If you think of the house as the center of many residential activities: cooking, eating, sleeping, and the fact that they abandoned the house soon afterward the cremation, this is pretty compelling evidence of the careful treatment of the child," Potter said.
While the findings certainly provoke questions about the story of this particular death, for Potter and other archeologists, the site is perhaps even more valuable for what it says broadly about the lifestyles of the early people who lived in the region.
Although many of the specifics are still under debate, researchers generally believe that the first people in North America came across the Bering Land Bridge from Siberia some time near the end of the last ice age, around 13,000 years ago or earlier. Archaeological evidence from this time period is scanty, however, especially in the northern regions adjacent to the Bering Sea, known as Beringia.
Scientists have discovered only a handful of known houses in North America from the continent's first 2,000 years of human occupation. And, except for the one at Upper Sun River, those houses are in the lower 48 states or at Ushki Lake in Siberia. Ushki Lake also includes the only known burial site from this time period in Beringia.
The stone tools from contemporaneous sites in central Alaska fit into a category known as microblade technology, which consists of small, stone, razor-blade-like pieces set into larger organic points. In contrast, the more well-known Clovis people of central North America did not make microblades. In fact, the stone artifacts, along with the house structure and the types of animal remains found at Upper Sun River appear more similar to those of Siberia's Ushki Lake than to anything from the lower 48 states.
"We've got this basic technological organization system that links Alaska with the Old World," Potter said.
Researchers have debated over whether the people in central Alaska during the late Pleistocene and early Holocene were all part of one larger cultural group or whether they belonged to different groups. The tools and other remains at Upper Sun River, and their similarities to some others in the region, support the former scenario, Potter and his colleagues say.
Differences exist among the sites, but these may reflect this people's versatility, with different members carrying out different tasks, such as hunting large game or foraging for small mammals and birds, during different times of year, the researchers argue.
Throughout the excavation, Potter's groups worked closely with leaders of the Healy Lake Tribe and other native groups that live near the Upper Sun River site.
"Our consultation with the local Native groups is not only an ethical imperative in archaeology today, it has been a fulfilling and productive partnership, from my perspective," said Potter.
"We strove to be diligent with full and open negotiations from the time of discovery and before, and we have worked together to build a foundation for continued work on this find and for future discoveries."
This research was supported by the National Science Foundation.