Stone Towers Are Decoded as Earliest Solar Observatory in the Americas

By JOHN NOBLE WILFORD

Early people in Peru, like others in antiquity, went to great lengths to track the rising and setting of the sun through the seasons as a guide for agriculture, an object of worship and a mystical demonstration of a ruler’s power.

Archaeologists have now discovered that a line of elaborate stone towers erected on a low ridge by Peruvians 2,300 years ago formed an artificial toothed horizon with narrow gaps at regular intervals for making alignments almost exactly spanning the annual arc of the sun.

This is the earliest known solar observatory in the Americas. The site precedes by several centuries similar monuments by the Maya in Central America and by almost two millenniums solar observatories of the Inca civilization in Peru.

In a report in the current issue of the journal Science, a Peruvian archaeologist and a British archaeoastronomer wrote that the 13 towers, varying in height from 6 to 20 feet and extending 1,000 feet, are clearly visible from an imposing complex of concentric circles of relatively well-preserved walls enclosing ceremonial buildings. They said the position of the towers in relation to observation points inside the walled complex was firm evidence that this was a place for solar study in calendar-making and ritual ceremonies and feasts of sun cults.

The observatory, known as the Thirteen Towers of Chankillo, is in the Casma-Sechin River Basin of the coastal Peruvian desert, 240 miles north of Lima. Since the 19th century, archaeologists have speculated on the function of the walls and towers, whether the complex was a temple, the setting for ceremonial battles or a fort, the most common explanation.

Ivan Ghezzi, a doctoral student at Yale University who is studying ancient Peruvian warfare, visited Chankillo to investigate its battlements. Part of the complex did appear to be fortifications.

“In the first hours of measurements,” Mr. Ghezzi said in a telephone interview from Lima, “we realized the nature and importance of the towers.”

Clive Ruggles, an archaeoastronomer at the University of Leicester in England, joined Mr. Ghezzi, who is also director of the National Institute of Culture, in Peru, in the investigation. They concluded that Chankillo provided “evidence of early solar horizon observations and of the existence of sophisticated sun cults,” beginning in the fourth century B. C.

Clark Erickson, an Andean archaeologist at the University of Pennsylvania who was not involved in the research, said he was convinced by the new findings. They are important, he said, because they reveal “what was going on in the heads of these people.”