Machu Picchu grown rapidly. In 1912, 1914 and 1915, Bingham removed thousands of artifacts from Machu Picchu—ceramic vessels, silver statues, jewelry and human bones—and took them to Yale University for further study, supposedly for 18 months. Yale instead kept the artifacts until 2012, arguing that Peru lacked the infrastructure and systems to care for them. Eliane Karp, an anthropologist and wife of former Peruvian President Alejandro Toledo, accused Yale of profiting from Peru's cultural heritage. Many of the articles were exhibited at Yale's Peabody Museum. In 2006, Yale returned some pieces but kept the rest, claiming this was supported by federal case
Machu Picchu who performed heavy physical labor (such as the Mit'a) and/or served in the Inca military. Not only people were suspected to have immigrated to Machu Picchu, there were several animal bones found that were not native to the site. Most animal bones found were from llamas and alpacas. These animals naturally live in altitudes of 14000 ft above sea level rather than the mere 8000 ft Machu Picchu rests on. Most likely, these animals were brought in from the Puna region for meat consumption and for their pelts. Guinea pigs were also found at the site in special burial caves,