The Peruvian government is threatening to sue Yale University for the return of all the artifacts found at Machu Picchu. There's no dispute that Peru gave Bingham permission to take the artifacts to Yale for further study. But Peruvian authorities say they have documents specifying that the material had to be returned within 18 months. It has now been more than 90 years. Yale says that Peruvian law in the 1900s "gave Yale title to the artifacts at the time of their excavation and ever since."

Three years of negotiations have not yet resulted in a solution. After Peru's Congress held public hearings in November, Yale offered in a Dec. 8 letter only to return "a substantial number" of the pieces. The National Geographic Society, which helped sponsor Bingham's Machu Picchu expeditions, is clear on where it stands: "The Society's opinion...is that the artifacts excavated from Peru during these joint expeditions were on loan, belong to Peru, and should be returned to Peru," says spokesperson Barbara Moffet.

Around the world, countries that were the source of archaeological treasures that now reside in the world's major museums are clamoring for the return of their cultural patrimony. Mexico is pressuring the Austrian government to return an Aztec headdress made of more than 450 brilliant green Quetzal feathers. The important national symbol is displayed at the Vienna ethnography museum, while a mere replica is shown at Mexico's national anthropological museum.

Mexican President Vicente Fox intends to press Austrian President Heinz Fischer about the headdress at a summit of Latin American and European leaders in Vienna in May -- the second such request he will have made to Fischer in a year. "It is an archaeological piece of incalculable value for the history of our nation," Mexican Foreign Minister Luis Ernesto Derbez said in a Jan. 12 news conference.

For Peru, recovering the Machu Picchu artifacts is a matter of pride -- and economics. Tourism is a major source of revenue, bringing in around $1.2 billion last year. Machu Picchu is the country's biggest draw: More than 400,000 foreign tourists visited in 2005, a 68% jump from two years earlier.

"Tourism plays an increasingly important role in the economies of countries like ours," says Luis Guillermo Lumbreras, an archaeologist and director of Peru's National Institute of Culture. For Peruvians, he says, being able to view evidence that their forebears lived in highly developed civilizations "is an important source of national pride."

Kenneth Ames, a Portland State University archaeologist who is currently president of the Society for American Archaeology, says that foreign archaeologists today are generally required to study all artifacts they find in the host country and are not permitted to remove them. "Everyone realizes that what were once standard operating procedures no longer are," he says.

Negotiations are continuing, and Peruvian officials hope to resolve the controversy with Yale amicably before President Alejandro Toledo leaves office July 28. Toledo, the country's first indigenous president, is married to an anthropologist and has taken a special interest in securing the return of the Machu Picchu artifacts. Lumbreras says Peru would like to have a world-class museum completed before 2011, the 100th anniversary of Machu Picchu's "rediscovery."

For Yale, the dispute marks the souring of a relationship that has been quite positive over the years. Professor Richard Burger, Yale's resident expert on Andean archaeology, is co-curator of an exhibit -- Machu Picchu: Unveiling the Mystery of the Incas -- at the university's Peabody Museum of Natural History.

When I visited the exhibit in October, Burger gave a fascinating talk about Bingham's Peruvian expeditions and spoke with pride of Yale's stewardship of the artifacts collection. I contacted him by e-mail for a comment on the current dispute, and he referred me to university officials, but mentioned that "Machu Picchu is still astonishingly beautiful."

Peruvians realize that Yale archaeologists did valuable work, and the Peabody exhibit, which earlier toured several U.S. cities, surely sparked interest among Americans to visit Machu Picchu. In addition to the artifacts displayed, Yale curators recreated the house of an Incan king, complete with life-size figures in typical garb and sound effects including conversations recorded in Quechua, the native language. "It's good for tourism that an exhibit like that has been shown in the U.S.," says Lumbreras. "Still, we'd like the objects back."

It all boils down to whether the few existing artifacts from one of the world's most fascinating archaeological sites should remain at the university that nearly a century ago was granted the rare privilege of excavating and studying them, or whether they should be returned to the proud descendants of the Incas.

The objects' possible return is being watched with some concern by museum directors around the world, who fear a flurry of similar requests from other countries.