Machu Picchu may be decades older than previously thought

Radiocarbon dating of human bones and teeth in Peruvian ruins indicate that the Inca first lived at the citadel around 1420, not after 1440

After scientific testing, historians face the task of rethinking the dating of the 15th-century Inca site Machu Picchu

After scientific testing, historians face the task of rethinking the dating of the 15th-century Inca site Machu Picchu

The Inca may have built the Andean citadel of Machu Picchu decades earlier than previously thought: A team of researchers report in the journal Antiquity that scientific testing of human remains from the Peruvian site’s ruins revealed that the Inca first lived at the site around 1420 rather than after 1440, as has traditionally been accepted. The discovery challenges scholars’ current reconstruction of Inca history and may also push back the date for the initial expansion of their empire.

Scholars previously used Spanish colonial records to establish the earliest date for Machu Picchu, which served as an Inca royal estate and palace. Based on these accounts, Emperor Pachacuti built the site after conquering the region during his campaigns of expansion, which ultimately led to the creation of the Inca empire. In this reconstruction of history, Pachacuti came to power in 1438, meaning that significant events under his reign had to fall after this date.

Now, however, testing of human bones and teeth found in 1912 in three burial caves at Machu Picchu with a radiocarbon dating technique called accelerator mass spectrometry (AMS) has made it possible to establish more accurate dates and underline the limitations of relying on Spanish records.

“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,” the researchers write. “Until recently, archaeological work at Cuzco has produced few radiocarbon dates for Inca-period sites, and even recent in-depth studies have relied on Spanish chronicles for dating.”

The bones and teeth tested, representing around 26 individuals, appear to be the remains of people who worked there as retainers. Hundreds of retainers lived at Machu Picchu year round to look after the site, though the Inca elite only stayed seasonally.

“As it is believed that the bone samples relate to site retainers, these interments should span the history of Machu Picchu from its early use as a palace until its abandonment,” the researchers write. Their results showed that the site was inhabited continuously from around 1420 to 1530, with hardly any evidence of use after the Spanish conquest of Peru in 1532.

Archaeologists may now have to rewrite the history of the early Inca empire. “If the calibrated AMS dates presented here are supported by future analyses, the traditional text-based estimate of AD 1438 for Pachacuti’s accession to the throne and his initial conquests would have to be moved back by at least two decades,” the researchers write.

Considered a masterpiece of Inca art, architecture, urbanism and engineering, Machu Picchu has been a Unesco World Heritage Site since 1983.