Archaeologists and museum directors are paying close attention to a lawsuit in which the Peruvian government demands that Yale University return artifacts collected more than 90 years ago at Machu Picchu, the Andean redoubt that is believed to have been the last major settlement of the Inca empire. The university and Peru reached an agreement on the artifacts in 2007, but Peruvian activists and scholars objected to it so strongly that it fell apart.