Neanderthal bones revealing a family group who practiced cannibalism. Geneticanalysis shows they were highly inbred; with a population nearing extinction.
The Tunnel of Bones
In 1994, speleologists exploring the El Sidrón cave system in Asturias, northern Spain, discovered human remains. Initially thought to be casualties of the Spanish Civil War, subsequent analysis revealed a far older story. The bones belonged to Homo neanderthalensis and dated back approximately 49,000 years. Excavations in a small chamber, now called the "Galería del Osario" or Tunnel of Bones, eventually uncovered more than 2,500 fossil elements.
These remains represent at least 13 Neanderthal individuals. The group was composed of seven adults (three males and four females), three adolescents, two juveniles, and one infant. The bones were jumbled together, showing clear signs of butchery. Cut marks, percussion fractures, and flakes are consistent with techniques used to strip meat from bone and extract nutritious marrow. This evidence points to an episode of cannibalism, though whether it was due to starvation or conflict with a rival group remains unknown. The remains were likely deposited in the cave all at once, possibly washed in through a sinkhole from the surface above.
A Family's Genetic Secrets
The exceptional preservation conditions at El Sidrón allowed for the successful extraction of ancient DNA from the remains. Analysis of mitochondrial DNA (mtDNA), which is passed down through the maternal line, provided a detailed social snapshot of the group. The three adult males shared the same mtDNA lineage, while the three adult females each had different lineages. This genetic pattern suggests a patrilocal social structure, where females would leave their birth groups to live with their mates.
Genomic analysis uncovered a very low level of genetic diversity within the group, indicating a high degree of inbreeding. Skeletal analysis supports this, revealing 17 congenital anomalies across the remains, such as cleft vertebrae and a misshapen kneecap. These types of birth defects are more common in small, isolated populations with limited mating options. The genetics of the El Sidrón family show a population under demographic stress, possibly nearing local extinction.
Analysis of hardened dental plaque, or calculus, has also showed information about their diet and behavior. The El Sidrón Neanderthals ate a plant-based diet of mushrooms, pine nuts, and moss, with no evidence of meat detected in the calculus of the individuals studied. One individual with a dental abscess appears to have been self-medicating, as their plaque contained DNA from the poplar tree, a natural source of salicylic acid (the active ingredient in aspirin), and the antibiotic-producing mold Penicillium.
💡Fun Facts
DNA analysis confirmed the El Sidrón Neanderthals possessed the FOXP2 gene, which in modern humans is associated with language abilities.
The dental calculus of one individual contained traces of bitter-tasting plants like yarrow and chamomile, suggesting they were consumed for medicinal purposes rather than for flavor.
Researchers found microscopic wood fibers embedded in the dental plaque, suggesting the Neanderthals used their mouths as a "third hand" for tasks like processing materials.
The remains of the 13 individuals were found mixed with about 53 stone tools made from a local yellowish flint.
The El Sidrón cave is an active archaeological site and is not open to the public. However, artifacts and interpretations are on display at the nearby Archaeological Museum of Asturias. Museum hours are Wednesday-Friday 9:30 AM-8:00 PM; Saturday 9:30 AM-2:00 PM & 5:00 PM-8:00 PM; Sunday 9:30 AM-3:00 PM. Closed Monday and Tuesday.
Admission
Free entry to the Archaeological Museum of Asturias.
Accessibility
The Archaeological Museum of Asturias is located in a historic building in Oviedo and is wheelchair accessible.