Maybe it is just a pile of shells to you, but to an archaeologist...
One type of site that some archaeologists love to investigate is the shell midden, or kitchen midden. A shell midden is a heap of clam, oyster, whelk, or mussel shells, obviously, but unlike other types of sites it is the result of a clearly recognizable single-activity event. Other kinds of sites, such as camp sites, villages, farmsteads and rockshelters, have their attractions, but a shell midden was created by and large for one purpose: dinner.
Diets and Shell Middens
Shell middens are found throughout the world, on coastlines, near lagoons and tidewater flats, along major rivers, in small streams, wherever some variety of shell fish is found. Although shell middens also date from pretty much all of prehistory, many shell middens date to the Late Archaic or (in the old world) Late Mesolithic periods.
The Late Archaic and European Mesolithic periods (around 4,000-10000 years ago, depending on where you're at in the world) were interesting times. People were still essentially hunter-gatherers, but by then were settling down, reducing their territories, focusing on a broader range of food and living resources. One often used way to diversify the diet was to depend on shellfish as a reasonably easy to obtain food source.
Of course, as Johnny Hart once said, “the bravest man I ever saw was the first to devour an oyster, raw”.
Studying Shell Middens
According to Glyn Daniel in his great history 150 Years of Archaeology, shell middens were first explicitly identified as archaeological in context (i.e., built by humans not other animals) during the mid-nineteenth century in Denmark.
In 1843, the Royal Academy of Copenhagen led by archaeologist J.J. Worsaee, geologist Johann Georg Forchhammer, and zoologist Japetus Steenstrup proved that the shell heaps (called Kjoekken moedding in Danish) were in fact cultural deposits.
Archaeologists have studied shell middens for all kinds of reasons. Studies have included
- calculating how much dietary meat there is in a clam (only a few grams in comparison to the weight of the shell),
- food processing methods (steamed, baked, dried),
- archaeological processing methods (sampling strategies vs. counting the entire midden--which nobody in their right mind would do),
- seasonality (what time of year and how often were clambakes held),
- other purposes for the shell mounds (living areas, burial sites).
Not all shell middens are cultural; not all cultural shell middens are solely the remnants of a clambake. One of my favorite shell midden articles is Lynn Ceci’s 1984 paper in World Archaeology. Ceci described a series of weird donut-shaped shell middens, consisting of prehistoric pottery and artifacts and shell located on hillsides in New England. She figured out that they were in fact evidence of early EuroAmerican settlers reusing prehistoric shell deposits as fertilizer for apple orchards. The hole in the middle was where the apple tree stood!
Shell Middens through Time
The oldest shell middens in the world are about 140,000 years old, from the Middle Stone Age of South Africa, at sites like Blombos Cave. There are fairly recent shell middens in Australia, within the last couple hundred years anyway, and the most recent shell middens in the United States that I’m aware of date to the late 19th century and early 20th century AD, when the shell button industry was in progress along the Mississippi River.
You can still find heaps of freshwater mussel shells with several holes punched out of them lying along the bigger rivers of the American midwest. The industry nearly obliterated the freshwater mussel population until plastics and international trade put it out of business.
Shell Midden Archaeology
Sites: Stallings Island, USA; Vuelta Limon, Mexico; Plum Piece, Lesser Antilles; Da But, Vietnam; Capelinha (Brazil); Chilca, Peru; Natsushima, Japan, San Blas, Mexico, Blombos Cave, South Africa.
Cultures: Hoabinhian, Chantuto Phase, Jomon Tradition, Ertebølle-Ellerbeck culture, Howiesons Poort.
Attached to this paper is an extensive bibliography, extensive even by my lights. Maybe somebody will find it useful.