History of Machu picchu
Machu Picchu was believed (by Richard L. Burger, professor of anthropology at Yale University) to have been built in the 1450s. However, a 2021 study led by Burger used radiocarbon dating (specifically, AMS) to reveal that Machu Picchu may have been occupied from around 1420–1530 AD. Construction appears to date from two great Inca rulers, Pachacutec Inca Yupanqui (1438–1471) and Túpac Inca Yupanqui (1472–1493). There is a consensus among archaeologists that Pachacutec ordered the construction of the royal estate for his use as a retreat, most likely after a successful military campaign. Although Machu Picchu is considered to be a "royal" estate, it would not have been passed down in the line of succession. Rather it was used for 80 years before being abandoned, seemingly because of the Spanish conquests in other parts of the Inca Empire. It is possible that most of its inhabitants died from smallpox introduced by travelers before the Spanish conquistadors arrived in the area.
Studies show that, according to their skeletal remains, most people who lived there were immigrants from diverse backgrounds. They lacked the chemical markers and osteological markers they would have if they had been living there their entire lives. Instead, research into skeletal remains has found bone damage from various species of water parasites indigenous to different areas of Peru. There were also varying osteological stressors and varying chemical densities suggesting varying long-term diets characteristic of specific regions that were spaced apart. These diets are composed of varying levels of maize, potatoes, grains, legumes, and fish, but the overall most recent short-term diet for these people was composed of less fish and more corn. This suggests that several of the immigrants were from more coastal areas and moved to Machu Picchu where corn was a larger portion of food intake. Most skeletal remains found at the site had lower levels of arthritis and bone fractures than those found in most sites of the Inca Empire. Inca individuals who had arthritis and bone fractures were typically those who performed heavy physical labor (such as the Mit'a) or served in the Inca military.