Radiocarbon dating confirms 10,000 years of continuous human occupation in the Pyrenees

The Obagues de Ratera rock-shelter has been continuously occupied for 10,000 years: from the Mesolithic to the 20th century. Credit: GAAM-UAB

Researchers from the Universitat Autònoma de Barcelona (UAB) have created an open database with 124 carbon-14-dated samples that have made it possible to construct the chronological sequence of 380 sites located in the Aigüestortes i Estany de Sant Maurici National Park. The evidence confirms continuous human occupation for several thousand years at sites found at more than 2,000 meters (6,562 feet).

Researchers from the Universitat Autònoma de Barcelona (UAB) have created a database of carbon-14-dated samples that has aided in building a chronological framework of human occupation throughout the Holocene at the Aigüestortes i Estany de Sant Maurici National Park (PNAESM), a high-mountain area where archaeological research has documented 380 sites. The new database, which is openly accessible, is made up of 124 dated samples from 45 sites and represents "the first openly published systematic series of absolute dates of a high-mountain area of the Pyrenees," highlights Ermengol Gassiot, director of the High Mountain Archaeology Group (GAAM).

The study, now published with the database, presents and analyzes the data obtained, alongside laboratory reports, details on the types of samples that were dated, contexts and sites, as well as the code for the analyses carried out so they can be replicated. The study was published in Archeologica Data .

The results confirm evidence of continuous human presence above 2,000 meters (6,562 feet) for more than 10,000 years and point out that three of the excavated sites present continuous dates spanning several thousand years. The oldest one, with the first occupation occurring 10,000 years ago, is the Obagues de Ratera rock shelter, at 2,320 meters (7,612 feet); followed by the Cova del Sardo (1,780 meters/5,840 feet), with human occupations extending back 7,500 years; and the Portarró rock shelter (2,280 meters/7,480 feet), with occupations dating back 7,300 years.

Map of the site of the Aigüestortes i Estany de Sant Maurici National Park, registered and dated in the study. Credit: GAAM-UAB

The study highlights that the Obagues de Ratera rock shelter was occupied during the Mesolithic, the transition from the Mesolithic to the Neolithic and throughout the Neolithic, the Chalcolithic, the Early and Middle Bronze Age, the beginning of the Iron Age, the High Middle Ages (Visigothic period), and the 19th and 20th centuries. "This is an exceptional temporal sequence that very few sites in Catalonia have, not only in the high mountains," says Guillem Salvador, co-author of the research.

Excavations in the rock shelter confirm that shortly after the last glacial period, in a context of progressive climate warming in which small cirque glaciers still existed in the area, small groups of hunter–gatherers already frequented the alpine areas of the mountain range.

The analyses show that there were periods in which human activity in high-mountain areas clearly intensified, such as at the end of the Neolithic (5,300 to 4,500 years ago) and later in late antiquity and at the beginning of the medieval period. They also reveal the dates of the first architectural remains, dating back to prehistory, such as at the Portarró rock shelter, where the archaeological digs led to the documentation of constructions with a dry-stone base and wood dating back 5,000 years. It is currently the oldest known example of stone architecture in the Pyrenees.

"The data allows us to track this information and shows a highly relevant fact: The sites located in high-mountain areas, places which for us would be inaccessible and inhospitable, often present long periods of human occupation. Many other sites in which we carried out small-scale sampling also show us that they were occupied or inhabited at several different times," Gassiot explains.

A project spanning more than 20 years of research

The article covers 20 years of sustained research conducted by Gassiot and his collaborators at the PNAESM. Following various statistical procedures, it presents quantitative elements that validate the inferences made over the years and help specify thresholds of intensity in the over- or underrepresentation of data. It also refines the chronological intervals.

"For example, one of these periods is the era of Ötzi, the Tyrolean Iceman. Here, the data points to the fact that when Ötzi crossed the Tisenjoch glacier (and was killed) some 5,300 years ago, other high-mountain areas such as the PNAESM experienced a marked increase in human presence above 2,000 meters (6,562 feet)," Gassiot points out.

The 380 archaeological sites registered until now at the PNAESM include enclosures of different sizes and purposes; possible housing structures; rock shelters that take advantage of glacial accumulations of large stone blocks, many of which contained structures such as walls sep…