By Peter N. Spotts writer of The Christian Science Monitor
The Christian Science Monitor
The welcome mat is rustic: prairie grass flattened by a pickup truck.
To a visitor walking up a slight rise to the tracks' end at a pile of dirt and two makeshift worktables, it appears that no one is home. Suddenly, a hand hefting a bucket sprouts from the ground, vanishes, and is replaced by a human.
The human is Jim Mertz, a volunteer helping archaeologists who are trying to answer fundamental questions about the ancient inhabitants of this site, known as Cahokia.
Archaeologists estimate that at a time when the Normans were consolidating their hold on a newly conquered England, central Cahokia covered five square miles, held more than 100 earthen mounds ranging from the mundane to the monumental, and was home to as many as 20,000 people.
Greater Cahokia appears to have embrace communities with dozens of additional mounds in what are now St. Louis and East St. Louis, forming what many archaeologists say was the heart of the Mississippian culture.
Yet like the ancient Anasazi, whose cultural center in New Mexico's Chaco Canyon peaked between AD 850 and 1250, the Mississippians at Cahokia melted away, perhaps to merge with what became more modern groups. By 1400, only the mounds remained as silent testimony to a once-thriving cultural center.
Researchers are trying to pin down the factors that led to the rise and fall of Cahokia, as well as details about how the society evolved over time. Recent discoveries of Mississippian communities on the Illinois plateau, which rises above the Mississippi River plain some five miles east of Cahokia, are prompting some researchers to overhaul their views of how the society was organized and how it maintained its cohesion.
Today, notes University of Illinois archaeologist Timothy Pauketat, Cahokia mounds represent "a linchpin in the archaeology of eastern North America."
Mr. Mertz is scraping his way into one of them, known as Mound 34.
He clambers up a stepladder and out of a rectangular trench with corners as sharply defined as the crease on a sailor's dress whites. He empties his bucket onto a makeshift sieve, then sweeps his gloved hand back and forth, breaking up clods and sifting through the dirt in search of archaeologists' "black gold" - charcoal.
"If we can get enough charcoal, we can get a good date" on the layer of soil that contained the specimens, says Mertz, referring to radiocarbon dating techniques.
Getting a "good date" on the mound's contents is critical to answering several questions, notes John Kelly, a research associate at Washington University in St. Louis and the lead scientist on the Mound 34 dig. With less that 1 percent of the historic site excavated, researchers are still trying to pin down the order in which the mounds were built and rebuilt. The sequence is expected to help define the changes that took place in the society's structure over time.
An exporter of culture
More intriguing is the potential role Cahokia played in developing cultural and religious symbols and ideas that it exported to more distant groups. Dr. Kelly notes that Mound 34 appears to have been a ceremonial site centering on war and hunting. Unique shell artifacts found in 1956, but less rigorously dated, also have cropped up in mounds at Spiro, Okla. …