`Mounds' called oldest structures in North America Story-Date: 04:46 a.m. PST Friday , September 19, 1997 ------------------------------------------------------------ `Mounds' called oldest structures in North America Los Angeles Times Louisiana: Discovery changes view of early inhabitants. A team of researchers reports in today's edition of the journal Science the discovery of the oldest reliably dated human-made structure in the New World, a 5,400-year-old earthen mound at Watson Brake, La., that is almost 2,000 years older than nearby sites. The circular mound, as tall as a two-story house, forms an enclosure nearly 300 yards in diameter, but its purpose is not yet clear. The researchers said the discovery of this and other mounds in Louisiana and Florida suggest that the earliest Americans, long thought to be simple hunter-gatherers who roamed the countryside in small, mobile bands, were actually capable of organizing and executing large civil-engineering projects. The discovery "totally changes our picture of what happened in the past," said archaeologist Vincas Steponaitis of the University of North Carolina at Chapel Hill. "We are reassessing our whole theory of what we thought about the evolution of societies," said National Park Service archaeologist Mike Russo of the Southeastern Archeological Center in Tallahassee, Fla. "We once thought society was very slow to develop in North America. In fact, there were numerous societies here capable of monumental architecture much earlier than we had ever expected." Public-works projects And what is becoming clear, he said, is that some of these early groups had a relatively comfortable existence, with ample supplies of food and enough time on their hands to undertake massive public-works projects. Such societies had to have a rich biological niche to support relatively large populations without the benefit of agriculture, he said, but they also had to have "social conventions that would allow them to do something innovative, like build mounds. They were a little less conservative than some of the other societies around them." Although archaeologists have often tended to ignore them and the general public is often unaware of their existence, thousands of human-made mounds dot the East and Midwest. Shaped like serpents, giant cones and square platforms, these 2,000- to 3,000-year-old mounds in some cases have been shown to serve as ceremonial centers, slaughterhouses and homes. More often, however, their purposes have remained mysterious, lost in the mist of civilizations that had not yet invented writing or other pictorial displays. Sites in Louisiana, Florida Still-older mounds are being found in Louisiana and Florida, where the rich mixture of wildlife and marine life from bays and rivers was capable of supporting larger indigenous populations. One of the oldest well-documented such sites was Poverty Point in Northeastern Louisiana, about 100 miles from the new find at Watson Brake. Poverty Point, named for a nearby plantation, was built about 3,500 years ago by a people who clearly had prospered from trading. Archaeologists studying it have unearthed flint stone from what is now Ohio, soapstone from northern Alabama and Georgia, copper from Michigan, crystal quartz from Arkansas and chert from Missouri. Russo said that community seemed "unusually precocious," apparently springing up in full bloom without any historical predecessors. The much older Watson Brake discovery, he said, "explains Poverty Point." Although researchers have not yet found any direct links between the two sites, it seems clear that Watson Brake is a more primitive example of the planning that later characterized Poverty Point. The shape of the mound was hidden by a dense forest of pine at the site until the 1980s, when some of the trees were clear-cut. A recreational archaeologist named Reca Jones then recognized the overall outlines of the circular mound. Eventually, she and others attracted the interest of Joe Saunders of Northeast Louisiana University, a state archaeologist. Visiting Watson Brake, he noted an unusual weathering pattern in the mound soil, indicating not only that it was human-made but also unusually old. Using both conventional radiocarbon dating and newly developed soil-dating techniques, his team concluded that construction of Watson Brake began about 5,400 years ago and ended 400 years later. "There have been similar dates for other mounds in the area, but they have always been ambiguous," Saunders said. "One date would be old, one would be much younger. Ours are all old." The dating is very convincing, said archaeologist Jon Gibson of the University of Southwestern Louisiana. "There's just no question about it." ------------------------------------------------------------