A preliminary estimate for one individual at Sohornu cave in Andrín, Asturias, puts marine sources at about 55% of that person’s dietary protein. The commonly cited age of about 8,000 years remains provisional, while finds at El Mazo offer a separate record of coastal food gathering.
A marine signal at Sohornu
The estimate concerns protein from marine sources, not the share of a person’s entire diet. It is described as based on isotope analysis of collagen, a protein preserved in bone that can retain clues about food sources.
Carbon isotopes can help distinguish marine from terrestrial protein sources. Nitrogen isotopes can indicate trophic position—the place a person or animal occupies in the food web. Collagen analysis does not provide a complete menu or measure the balance of fats and carbohydrates.
The discovery and excavation
Sohornu cave is near Andrín, in the municipality of Llanes, Asturias. Cavers Pablo Solares and Clara Zazo reportedly found a human mandible there in 2024. An excavation led by Pablo Arias and Alberto Martínez Villa concluded in summer 2025.
The excavation reportedly recovered remains identified as belonging to at least two adult males, as well as a deer antler. The preliminary protein estimate applies to one individual, not to all the remains or to Mesolithic people in the region as a whole.
Why the reported age is provisional
The remains have been described as about 8,000 years old, but that age is provisional. Marine foods can make radiocarbon ages appear older through the marine reservoir effect, so dating people who ate seafood requires an appropriate correction.
What El Mazo adds to the regional picture
A peer-reviewed study of El Mazo cave examined shell-midden deposits in stratigraphic units 114 and 115, dated to about 9,000 calibrated years before present. The researchers identified 19 taxa across the two units, including molluscs, crustaceans and an echinoid.
Limpets of the genus Patella and top shells (Phorcus lineatus) together accounted for about 88% of the minimum number of individuals counted in the assemblages. About 99% of recorded shells came from rocky shores. Measurements of Patella vulgata suggested that roughly 75–80% had been collected in the lower intertidal zone.
Those counts describe animal remains in a site’s deposits and patterns of collection; they do not measure the proportion of marine protein in one person’s diet. At El Mazo, sea urchins (Paracentrotus lividus) accounted for 6.86% of the minimum number of individuals in unit 114 and 10.04% in unit 115.
