Nearly complete 4,000-year-old bison skeleton and cave lion remains discovered in Navarra

A multidisciplinary team of researchers has discovered a nearly complete bison skeleton dating to around 4,000 years ago, along with remains of a cave lion (Panthera spelaea), an extinct species that disappeared about 12,000 years ago, in the Sima de Arrafela, located in the Urbasa and Andía Natural Park (Navarra, Spain). Among the specialists involved in the study is Dr Antonio Rodríguez-Hidalgo, from the Instituto de Arqueología-Mérida (CSIC-Junta de Extremadura) and an associated researcher at IPHES-CERCA.

The discovery, recently presented by the Government of Navarra, took place במסגרת a scientific intervention promoted by the Directorate-General for Culture – Institución Príncipe de Viana, with the participation of researchers from the University of the Basque Country (UPV/EHU), the National Museum of Natural Sciences (CSIC), and other national and international institutions. It is considered one of the most significant archaeological finds made in Navarra in recent decades.

An exceptional discovery in the Iberian Peninsula

The most remarkable find is a partially articulated bison skeleton dated by radiocarbon to the end of the Chalcolithic period, around 4,000 years ago. A copper arrowhead was found embedded between the animal’s ribs, providing direct evidence of interaction with human groups of the time. All indications suggest that the animal was wounded during a hunting attempt and later fell into the cavity.

Taphonomic studies, however, indicate that the bison did not die from the arrow wound or from the immediate impact of the fall. After plunging into the sinkhole, the animal appears to have rolled down the slope, stood up again, and wandered through the cavity before lying down and dying in a fetal-like position.

This detail turns the find into an exceptional testimony of the relationship between Chalcolithic communities and large wild fauna, offering a scene almost frozen in time, with a hunted animal preserved in a natural context for millennia.

Preliminary studies suggest that the specimen could belong to the European bison (Bison bonasus), although this identification still awaits genetic confirmation. If confirmed, it would represent the first evidence of this species in the Iberian Peninsula. Another possibility is that it belongs to the so-called “Clade X”, a poorly known genetic lineage for which no complete skeleton had previously been found.

According to palaeontologist Asier Gómez Olivencia (UPV/EHU), one of the scientific coordinators of the project, the assemblage is an exceptional discovery due to both its state of preservation and its scientific potential, as it may provide key information about late prehistoric fauna and human–megafauna relationships.

The dating also makes it the most recent bison documented in the Iberian Peninsula, opening new lines of research on the interactions between Chalcolithic communities and wild fauna. The animal, around four years old, may have weighed between 800 and 850 kilograms and would have coexisted with farming and herding communities in the area.

Research spanning decades

The first indications of remains in the cavity were already known since the 1980s, but recent investigations have culminated in a five-year scientific process that has allowed the systematic recovery and study of the assemblage.

The skeleton was recovered between 24 and 26 October 2025, in an intervention that required speleological techniques to work in a deep cavity. Since then, research teams have cleaned the bones, produced a preliminary inventory, and initiated metric studies, as well as sampling for genetic and isotopic analyses.

Cave lion remains and other species

The same intervention also yielded remains of a cave lion, the third documented in Navarra after the sites of Abauntz and Koskobilo, but the one that has provided the largest number of remains. In addition, remains of a capercaillie and a bird of prey were identified, helping to expand knowledge of prehistoric ecosystems in the region.

Together, these remains turn the Sima de Arrafela into a true “time capsule”, preserving animals that fell into the cavity at different moments in the past and allowing detailed reconstructions of northern Iberian ecosystems.

A key assemblage for understanding bison evolution

Palaeontologist Jan van der Made, from the National Museum of Natural Sciences (CSIC), who is responsible for the morphological study of the assemblage, has highlighted the great scientific value of the discovery. Preliminary studies indicate that the skeleton has dimensions similar to those of male European bison, but smaller than those of the steppe bison (Bison priscus), which went extinct about 9,000 years ago.

This specimen could help clarify the evolutionary origin of the European bison, a species with a complex genetic history linked to hybridisation processes between the steppe bison and the aurochs, the ancestor of domestic cattle. The Arrafela bison may therefore provide key data on the genetic variability of these animals and the evolution of their populations over time.

IPHES-CERCA would like to congratulate the entire team responsible for this extraordinary discovery, as well as everyone involved in the project, among whom are researchers and close friends of our centre. This find, of enormous scientific interest and with wide media impact, represents a significant contribution to the knowledge of prehistoric fauna and the relationship between humans and large mammals in the Iberian Peninsula.