Radiocarbon dating rewrites the Inca Empire's timeline

Overview

Updated Oct 21

For more than half a century, archaeologists dated the Inca Empire from a timeline built in the 1940s on oral histories recorded by the Spanish cleric Miguel Cabello de Balboa. It gave the empire 94 years, from Pachacuti's rise in 1438 to the Spanish conquest that began in 1532. Radiocarbon dates from sites across the Andes now place Inca activity decades earlier.

At Saqsaywaman above Cusco, a University of Warsaw team found remodeling began around 1400 and construction accelerated around 1418; the results are in press at Antiquity. Bayesian modeling of 34 dates from Inca-only sites in northern Chile's Upper Loa River puts the start of Inca rule at 1401–1437, with a median of 1420. A separate Science report describes radiocarbon dating of a khipu, the knotted-cord record the Inca kept, that places its making shortly before the conquest began.

Why it matters

The new dates mean the Inca shaped South America for decades longer than scholars thought—and met organized resistance the empire never admitted to.

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Key Indicators

94 years

Span the traditional chronology gave the Inca Empire

Derived from a Spanish colonial chronicle; radiocarbon dates now contradict it.

AD 1420

Median radiocarbon date for Inca rule in northern Chile's Upper Loa River

Bayesian analysis of 34 dates from Inca-only sites, giving a modeled start of 1401–1437.

1432–1451

Ogburn's original radiocarbon range for the Inca outpost Chamical, Ecuador

Decades before the traditional conquest date of 1463. Later recalibrations of the same dates put the occupation closer to AD 1445.

30–60 years

Overlap between altiplano hillforts and Inca sites

Elizabeth Arkush's recalibrated dates show local fortifications built while the Inca were present.

Voices

Curated perspectives — historical figures and your fellow readers.

People Involved

Dennis Ogburn

Archaeologist; radiocarbon-dated the Inca outpost Chamical in Ecuador

Published a 2012 Radiocarbon paper calling for a new Inca chronology

Francisco Garrido

Archaeologist, National Museum of Natural History, Santiago, Chile

Excavated and dated Inca sites in the Copiapó Valley, northern Chile

Elizabeth Arkush

Archaeologist; studied hillforts (pukaras) on Peru's altiplano

Her recalibrated dates show Inca and local occupations overlapped decades

Erik Marsh

Archaeologist and radiocarbon expert, CONICET, Argentina

Says a full replacement for the traditional chronology does not yet exist

Julia Earle

Archaeologist, University of Warsaw

Her University of Warsaw team dated charcoal from Sacsayhuamán, near Cusco, finding renovations began around 1400 and full construction around 1418.

Organizations Involved

Science Magazine

Scientific journal and news outlet

Published the 2026 synthesis of new Inca radiocarbon dates

Peer-reviewed journal published by the American Association for the Advancement of Science.

CONICET

National research council

Home to radiocarbon expert Erik Marsh

Argentina's National Scientific and Technical Research Council, a major employer of Andean archaeologists.

Timeline

2012 October 2026

4 events Latest: October 14th, 2026 · 4 weeks ago

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October 2026
Science publishes synthesis of new Inca dates
Latest Research publication

Science magazine reports that radiocarbon dating across the Inca Empire shows the empire lasted longer and met more resistance than the traditional chronology held.
October 14th, 2026
Radiocarbon dating applied to an Inca khipu
Research publication

A Science report describes dating a khipu catalogued as KH0631, now in Munich, using a lock of hair. The result places the cord record's making shortly before the Spanish conquest began in 1532.
October 2026
2025
Inca chronology formally abandoned
Scientific meeting

Attendees at a meeting of Andean researchers at the Pontifical Catholic University of Peru vote unanimously to discard the traditional chronology.
2025
2012
Ogburn calls for a radiocarbon-based Inca chronology
Research publication

Dennis Ogburn publishes a Radiocarbon paper urging archaeologists to rebuild Inca chronology from radiocarbon dates alone after his dating of Chamical, Ecuador contradicted the traditional timeline.
2012

Scenarios

Unified radiocarbon chronology becomes the Inca standard

Likely Resolves by End of 2030

Discussed by: Erik Marsh (CONICET), Julia Earle (University of Warsaw), attendees of the 2025 meeting

Researchers combine Bayesian analyses of hundreds of radiocarbon dates from Inca sites across Ecuador, Peru, Chile, and Argentina into a single open chronology. That framework replaces the Spanish-derived timeline in textbooks and peer-reviewed work. Marsh cautioned in the Science piece that no such synthesis exists yet, but the momentum is toward one.

Radiocarbon evidence documents decades of local resistance

Likely Resolves by End of 2029

Discussed by: Francisco Garrido (National Museum of Natural History, Santiago), Elizabeth Arkush

As radiocarbon dating spreads to more sites, archaeologists document overlapping Inca and local occupations across the Andes: hillforts still being built after the Inca arrived, cemeteries excluding Inca goods. The single rapid-conquest story gives way to a patchwork of negotiation, cooperation, and resistance that lasted decades in each region.

Traditional chronology persists where radiocarbon can't reach

Possible Resolves by End of 2028

Discussed by: Erik Marsh, who notes no replacement framework exists yet

Textbooks and reference works continue to use the 94-year ethnohistoric timeline because radiocarbon uncertainty ranges remain too wide for fine-grained political history. The old dates survive in modified form wherever the science cannot yet contradict them with precision.

Historical Context

2 moments from history that rhyme with this story — and how they unfolded.

1949–1960

The radiocarbon revolution (1949–1960)

Willard Libby developed radiocarbon dating at the University of Chicago, announcing the technique in 1949 and winning the Nobel Prize in Chemistry in 1960. The method let archaeologists date organic material in absolute calendar years, overturning prehistories built on text-based assumptions and artifact typologies.

Then

Conventional chronologies for European prehistory were abandoned as radiocarbon dates pushed the Neolithic back thousands of years.

Now

Dating became a core archaeological tool, and text-derived histories were repeatedly tested against the physics of carbon decay.

Why this matters now

Today's Inca revision runs on the same mechanism: measurements of carbon decay challenging a history written by the empire's conquerors.

1970s–2010s

Thera eruption dating debate (1970s–2010s)

Radiocarbon dating of the volcanic eruption that buried the Aegean island of Thera (Santorini) produced dates around 1600 BCE, roughly a century earlier than archaeologists estimated from pottery and Egyptian links. The two camps argued for decades about which clock was right.

Then

No full reconciliation was reached, but radiocarbon forced archaeologists to question anchor dates they had treated as fixed.

Now

The debate showed how wide radiocarbon uncertainty ranges can stall consensus when the disagreement is under a century.

Why this matters now

It previews the Inca case, where radiocarbon dates run decades ahead of text-derived royal chronologies and the fight over a short empire is a fight about how much to trust each clock.