Scientists discover Machu Picchu could be at least two decades older than thought

Prior estimates based on Spanish colonial records unreliable, experts suggest

Machu Picchu may have been occupied by the Incas for two decades longer than historians previously believed, according to a new study.

Researchers used radiocarbon dating to test long-held beliefs, based on Spanish colonial records, that the iconic Andean heritage site was first used between 1440 and 1450.

Machu Picchu is thought to have been a retreat for royalty and the higher echelons of Inca society who wished to spend time away from the empire’s capital, Cusco.

Experts analysed more than two dozen samples of bone and teeth from people buried in four cemeteries around the Peruvian site, and discovered the imperial palace there may in fact have been up and running by 1420 – possibly even earlier.

Explaining the discrepancy, the authors of the new study said: “The scarcity of reliable radiocarbon measurements for Machu Picchu was the result of a widely held opinion among archaeologists working in the Andes that such analyses were unnecessary because the accurate dating of Inca sites such as Machu Picchu could be established on the basis of Spanish historical accounts.

“Until recently, archaeological work at Cusco has produced few radiocarbon dates for Inca-period sites, and even recent in-depth studies have relied on Spanish chronicles for dating. An ‘absolute chronology’ for the Inca period based on historical records was published by John Rowe in 1945 and remains the dominant chronological framework.

“There have been repeated calls for a re-evaluation of the Rowe chronology using radiocarbon analyses, but samples from short-lived materials with well-established provenance that can be tied to Inca imperial history have been difficult to find.

“Thus, the measurements reported here for samples from [emperor] Pachacuti's royal estate at Machu Picchu not only shed light on the chronology of Peru's most famous archaeological site, but also have implications for the ongoing debate over the document-based chronology of Inca imperial history.”

The study is published in Antiquity.

Machu Picchu is one of the world’s best known tourist sites. More than 1 million people visited every year before the coronavirus pandemic, which led officials to greatly reduce the numbers allowed in.