New research shows that Machu Picchu, an ancient Incan citadel set high in the Andes Mountains in Peru, was occupied from about 1420 to 1532 CE, with activity beginning two decades earlier than suggested by the textual sources.
Machu Picchu, located about 80 km (50 miles) from Cusco, Peru, is one of the most famous archaeological sites in South America.
The precise dating of the monumental complex, however, relies largely on documentary sources.
“Since its ‘scientific discovery’ in 1911, this Inca country palace has become widely recognized and is now probably the best-known archaeological site in South America,” said Yale University Professor Richard Burger and colleagues.
“In 1983, Machu Picchu was designated as a UNESCO World Heritage Site and was visited by over a million travelers each year.”
“Historical sources dating from the Spanish invasion of the Inca Empire indicate that Inca Emperor Pachacuti seized power in 1438 and subsequently conquered the lower Urubamba Valley where Machu Picchu is located.”
“Based on those records, scholars have estimated that the site was built after 1440, and perhaps as late as 1450, depending on how long it took Pachacuti to subdue the region and construct the stone palace.”
The researchers used accelerator mass spectrometry, an advanced form of radiocarbon dating, to analyze human samples from 26 individuals recovered from burial contexts at Machu Picchu.
The bones and teeth used in the analysis likely belonged to retainers, or attendants, who were assigned to the royal estate.
“The remains show little evidence of involvement in heavy physical labor, such as construction, meaning that they likely were from the period when the site functioned as a country palace, not when it was being built,” the scientists said.
The findings reveal that Machu Picchu was in use from about 1420 to 1530 — ending around the time of the Spanish conquest — making the site at least 20 years older than the accepted historical record suggests and raising questions about our understanding of Inca chronology.
“Until now, estimates of Machu Picchu’s antiquity and the length of its occupation were based on contradictory historical accounts written by Spaniards in the period following the Spanish conquest,” Professor Burger said.
“This is the first study based on scientific evidence to provide an estimate for the founding of Machu Picchu and the length of its occupation, giving us a clearer picture of the site’s origins and history.”
The findings also suggest that Pachacuti, whose reign set the Inca on the path to becoming pre-Columbian America’s largest and most powerful empire, gained power and began his conquests decades earlier than textual sources indicate.
“As such, it has implications for people’s wider understanding of Inca history,” Professor Burger said.
“The results suggest that the discussion of the development of the Inca empire based primarily on colonial records needs revision.”
“Modern radiocarbon methods provide a better foundation than the historical records for understanding Inca chronology.”
The results were published in the journal Antiquity.
Richard L. Burger et al. New AMS dates for Machu Picchu: results and implications. Antiquity, published online August 4, 2021; doi: 10.15184/aqy.2021.99