Isotope analysis reveals prehistoric Greek dietary practices

Simon Fraser University, the Greek Ministry of Culture, and the University of Bologna have conducted an isotope study on the dietary patterns of Mesolithic and Neolithic humans at Franchthi Cave, Greece. The report confirms a terrestrial-based diet with negligible consumption of marine resources during these periods.

Franchthi Cave, overlooking the Bay of Koilada in the Peloponnese, is one of Greece’s most significant prehistoric sites, spanning nearly 40,000 years of occupation. The site is stunningly beautiful, with a high vaulted arch at the cave entrance inviting visitors into an otherworldly space.

Excavated between 1967 and 1979, it provides a continuous record from the Upper Paleolithic through the Neolithic. The Mesolithic to Neolithic transition is characterized across Europe by the emergence of agriculture and a shift in dietary reliance from marine to terrestrial resources, especially in coastal areas. Previous isotope studies of Franchthi suggested minimal marine input despite its coastal location.

The new study builds on these earlier findings by employing high-resolution compound-specific isotope analysis of amino acids in human and animal remains to clarify dietary practices at Franchthi during the Lower Mesolithic and Middle Neolithic.

In the study, “High-resolution isotope dietary analysis of Mesolithic and Neolithic humans from Franchthi Cave, Greece,” published in PLOS ONE, researchers examined isotopic data from bone collagen of five humans and six animals from the Mesolithic and Neolithic layers at Franchthi Cave.

Accelerator mass spectrometry analysis confirmed two Lower Mesolithic humans (8700–8500 BCE) and three Middle Neolithic individuals (6600–5800 BCE).

Collagen was extracted and analyzed for bulk stable isotopes of carbon-13 (δ¹³C) and nitrogen-15 (δ¹⁵N) and compound-specific isotopes of individual amino acids. Radiocarbon dating provided temporal context, placing two individuals in the Lower Mesolithic (8700–8300 BCE) and three in the Middle Neolithic (6600–5800 BCE). Amino acid-specific proxies, including changes in carbon-13 (Δ¹³C) and nitrogen-15 (Δ¹⁵N) comparisons, were used to differentiate dietary sources and assess trophic positions.

Human carbon-13 (δ¹³C) and nitrogen-15 (δ¹⁵N) values indicate terrestrial diets dominated by animal protein, with negligible marine input. No isotopic signatures suggest substantial reliance on fish or other marine resources.

Essential amino acids like phenylalanine (Phe) and valine (Val) consistently placed the humans within the realm of terrestrial C3 plant consumers. Nitrogen-based proxies, such as changes in nitrogen-15 between glutamic acid and phenylalanine (Δ¹⁵NGlu-Phe), revealed trophic positions consistent with high terrestrial protein intake. Lower Mesolithic individuals exhibited values reflective of significant meat consumption, while Middle Neolithic individuals showed slightly more dietary variation.

Neolithic sheep displayed elevated nitrogen-15 values, suggesting they grazed on nitrogen-enriched coastal vegetation. Pigs and canids had omnivorous diets, likely linked to human-provided food scraps.

Humans from both periods primarily relied on terrestrial resources, including animal protein, and consumed limited or no marine food. Despite the numerous remains of shallow-water fish and sea shells at Franchthi, the consumption of such resources during the Lower Mesolithic was not significant enough to leave a distinct isotopic signature on the individuals analyzed.

Isotope results from the Middle Neolithic reveal that sheep were likely grazing on the shore and that humans relied on a diet consisting primarily of terrestrial animal protein, mostly meat and milk derived from the sheep.

Consumption of aquatic resources at Franchthi could have been at most occasional or seasonal for the individuals analyzed, but not significant enough amounts to be revealed by the amino acid data.

Analysis did not include samples with the highest density of fish bones (Late Upper Paleolithic, Upper Mesolithic, and Early Late Neolithic). While the findings are significant for the Lower Mesolithic and Middle Neolithic layers, they do not fully represent the extent of marine resource consumption at Franchthi Cave during the Mesolithic and Neolithic.

While the findings may seem unintuitive, that easy access to nearby marine food sources should be ignored in favor of terrestrial ones, the authors point out that Franchthi Cave was once located up to 2 kilometers from the coast.

In a 2018 study led by the University of Bern, “Flooding a landscape: impact of Holocene transgression on coastal sedimentology and underwater archaeology in Kiladha Bay (Greece),” published in the Swiss Journal of Geosciences, researchers determined that Kiladha Bay was above sea level.

Findings of the Kiladha Bay study indicate that the shoreline would have been much farther from Franchthi Cave than its modern location, with rising sea levels progressively inundating a floodplain into a bay starting around ~4300 BCE.

During the Neolithic, large portions of Kiladha Bay were above sea level. Human settlements and agricultural activity thrived on this now submerged land, complete with livestock and farmland that could have sourced the cave dwellers with food crops and sheep.

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