Uncovering Ancient Architecture: the Chaco culture of North America created skillfully coordinated structures that continue to mystify scholars centuries after their civilization flourished.

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Few signs of human habitation greet travelers along the road that leads to New Mexico's Chaco Canyon. The desolate landscape appears incapable of supporting ]fie.

Yet one thousand years ago an enigmatic people not only wrested a living from this harsh environment, they established a civilization that still evokes awe. UNESCO (United Nations Educational, Scientific, and Cultural Organization), which recognized the Chaco culture in 1987, pronounced it "remarkable for its monumental public and ceremonial buildings and its distinctive architecture--it has an ancient urban ceremonial centre that is unlike anything constructed before or since."

Chaco Canyon, abandoned by its builders some eight centuries ago, still tantalizes archaeologists and others with riddles involving its one-time inhabitants. Recently, in one of two newsworthy events, clues from ancient pottery resolved a mystery that had baffled scientists for decades.

Scholars had puzzled over a collection of tall, cylindrical pottery vessels that were found in abundance in Pueblo Bonito, the extensively excavated Great House in the heart of the canyon. Educated guesses as to their use ranged from drums to containers for sacred objects. But when anthropologist Patricia Crown of the University of New Mexico had some pottery fragments tested chemically, their function became clear: chocolate residue dating from 1000 AD indicated that these were ritual drinking cups much like those once used by the Maya.

The discovery meant that cacao beans used for making chocolate had reached the US Southwest long before the Spanish brought chocolate north with them. Furthermore, transporting cacao from its place of origin in the tropics to Chaco Canyon would have elevated both its cost and its prestige value. Just as Mesoamericans prized chocolate as an elite ceremonial beverage, the extravagant drink seemed destined for a privileged class in Pueblo Bonito at Chaco Canyon.

That premise jibes with previous discoveries like the burial site of two individuals whose possessions (and possible retainers) buried with them suggest great wealth and status. Nor is chocolate the first evidence of trade with Mesoamerica. At Salmon Ruin, a Chaco colony 45 miles north of the canyon, archaeologist Larry Baker tells of finding bird bones among some refuse in a storage room. "When we had them identified, we learned that they were from two macaws," he says. "One set of bones had been painted."

Many more macaws, along with abalone shell, turquoise, and copper bells, have been found at Pueblo Bonito. The presence of tropical macaws, like the traces of chocolate, points to trade with cultures far to the south. Even earlier, corn had arrived from Mexico to supplement a diet of game animals and wild plants.

The second item to make headlines was the publication of Stephen H. Lekson's wide-ranging, provocative new study of the region, "A History of the Ancient Southwest." In this breezily written work, Lekson presents two parallel narratives: one, his interpretation of the rise and demise of the Chaco culture and its contemporaries; the second, a survey of the personalities and worldviews that...