When crabs invite themselves to eat prehistoric people

Why did Mesolithic populations living more than 7,000 years ago on the European Atlantic coast eat crabs for 15 years? This deliberately provocative question corresponds to the state of research in archaeology. If these remains remained invisible to archaeologists for several centuries, it was because they did not see them, did not look for them, and neglected their informative potential. This first observation emerges from a bibliographic analysis of one hundred articles on shells. The latter are landfills that will concentrate, like conglomerates, the waste of their daily activities. They are rich in shells of marine origin, hence their name.

Thus, prehistoric Mesolithic populations living near the Atlantic Ocean and engaged in hunting, gathering, and fishing built shell mounds. Among the many components of these dumps have been identified: marine and terrestrial mammals, marine and terrestrial birds, marine fish, marine molluscs, coal, seeds, flint, and crustaceans such as crayfish and crabs. A database compiled by Catherine Dupont lists all these components of Mesolithic and Neolithic shell archaeological sites along the European Atlantic Arc. This makes it possible to make a quantitative assessment of the detection of crabs and the degree of their analysis. Among more than 300 Mesolithic shells recorded from Norway to southern Portugal, the crab was present by archaeologists in only 18% of them. This figure is probably an underestimate due to the smallness of the remains left behind by the crabs. Very often, the remains of crabs less than a centimeter in size are invisible to the naked eye during excavation, especially since they are often covered with sediment. However, only 6% of the publications devoted to the discovered Tortoise mounds indicate the use of sifting. We also note that 77% of sites for which more than two crab species were identified were sieved with fine meshes between 1 and 6 mm. On the other hand, for the sites where crabs were found, these animals were both identified and quantified for only a quarter of them.

Is this invisibility of archeological crabs used by hunter-gatherer-fisher populations fatal? True, after several thousand years of burial in the ground, the crabs discovered by archaeologists are most often reduced to fragments of broken claw tips and less often to fragments of the lower jaw or shell. The study of crabs requires fine sieving (<2 mm) of sediments from excavations. Many hours of relentless sorting began. For more than 20 years, Catherine Dupont and Yves Gruet have raised awareness among archaeologists in the field and painstakingly recovered the archaeological remains of crabs from sieve waste. This feedback from experience allows them to propose a methodology that allows the identification of crab species and the reconstruction of individual sizes from some fragments of a crab claw finger. The analysis of these remains in a well-studied archaeological context also highlights the differential preservation of crab remains according to their location in the middle of the shells. The lack of visibility of these faunal remains is confirmed by recent excavations at Beg-er-Ville (Morbien), located in northwestern France. The average weight of a crab fragment is only 0.15 g. Reconstruction tests carried out on a square meter at the site of Beg an Dorhenn (Finister) show that 9.55 g of archaeological crab remains can be equivalent to 13 kg of fresh whole crabs.

Prehistoric shell sampling at Houdik (Morbian, July 2021) (© C. Dupont)

In total, 13 species of crabs have been found on the northeastern coast of the Atlantic Ocean. The most recurrent are sona or korzh Cancer Pagurus (19 plots), green crab Carcinus maenas (16 plots), crab Puberty delay (7 places) and warty crab or stone crab Eryphia is warty (6 sites).

It is not easy to warn archaeologists about the presence of these animals at coastal archaeological sites and to convince them of their informative power. This article addresses this by listing, for example, the agents of accumulation of these crustaceans in a coastal context, the known uses of crabs, the environmental data they contain. A study by the authors at Beg-er-Vil shows that Mesolithic hunter-gatherers adapted their crab harvest to the available habitats with seven species. The image of the terroir opens before us. Every rock seems to have been explored, every stone turned over to fish out anything edible. Similar to what is observed for marine molluscs, there is the question of the transmission of fishing sites from generation to generation.

Thus, the crabs found in these shells provide us with information both about past coastal biodiversity through the human filter and about the interactions that existed between these prehistoric hunter-gatherer-fisher populations and the ocean.

Ill.  1
current individual on the seashore (© C. Dupont)
Ill.  2
Comparison of a modern crab (A and C) and a fragment of an archaeological mandible (B, Cabeço da Amoreira – Portugal) (© C. Dupont)

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