Posts Tagged ‘clam middens’


Scientists have reconstructed the cooking techniques of the early inhabitants of Puerto Rico by analysing the remains of clams.


Led by Philip Staudigel, who conducted the analysis as a graduate student at the University of Miami Rosenstiel School and is now a postdoctoral researcher at Cardiff University, the team has used new chemical analysis techniques to identify the exact cooking temperatures at which clams were cooked over 2500 years ago.

With cooking temperatures getting up to around 200oC according to the new analysis, the team believe the early Puerto Ricans were partial to a barbeque rather than boiling their food as a soup.

The study, which also involved academics from the University of Miami and Valencia College, has been published today in the journal Science Advances.

Whilst the results throw new light on the cultural practices of the first communities to arrive on the island of Puerto Rico, they also provide at least circumstantial evidence that ceramic pottery technology was not widespread during this period of history – it’s likely that this would be the only way in which the clams could have been boiled.

Lead author of the study Dr Philip Staudigel, currently at Cardiff University’s School of Earth and Ocean Sciences, said: “Much of peoples’ identity draws upon on where they came from, one of the most profound expressions of this is in cooking. We learn to cook from our parents, who learned from their parents.

“In many parts of the world, written records extend back thousands of years, which often includes recipes. This is not the case in the Caribbean, as there were no written texts, except for petroglyphs. By learning more about how ancient Puerto Rican natives cooked their meals, we can relate to these long-gone peoples through their food.”

In their study, the team analysed over 20kg of fossilised clam shells at the University of Miami’s Rosenstiel School of Marine and Atmospheric Sciences Stable Isotope Lab, which were collected from an archaeological site in Cabo Rojo, Puerto Rico.

The pre-Arawak population of Puerto Rico were the first inhabitants of the island, arriving sometime before 3000 BC, and came from Central and/or South America. They existed primarily from fishing, hunting, and gathering near the mangrove swamps and coastal areas where they had settled.

The fossilised shells, dating back to around 700 BC, were cleaned and turned into a powder, which was then analysed to determine its mineralogy, as well as the abundance of specific chemical bonds in the sample.

When certain minerals are heated, the bonds between atoms in the mineral can rearrange themselves, which can then be measured in the lab. The amount of rearrangement is proportional to the temperature the mineral is heated.

This technique, known as clumped isotope geochemistry, is often used to determine the temperature an organism formed at but in this instance was used to reconstruct the temperature at which the clams were cooked.

The abundance of bonds in the powdered fossils was then compared to clams which were cooked at known temperatures, as well as uncooked modern clams collected from a nearby beach.

Results showed that that the majority of clams were heated to temperatures greater than 100°C – the boiling point of water – but no greater than 200°C. The results also revealed a disparity between the cooking temperature of different clams, which the researchers believe could be associated with a grilling technique in which the clams are heated from below, meaning the ones at the bottom were heated more than the ones at the top.

“The clams from the archaeological site appeared to be most similar to clams which had been barbequed,” continued Dr Staudigel.

“Ancient Puerto Ricans didn’t use cookbooks, at least none that lasted to the present day. The only way we have of knowing how our ancestors cooked is to study what they left behind. Here, we demonstrated that a relatively new technique can be used to learn what temperature they cooked at, which is one important detail of the cooking process.”

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Research points to traditional custodians for clues to sustainable practices. Natalie Parletta reports.

Researchers in British Columbia, Canada excavate ancient shells from the beach of a “clam garden” — a constructed rock-face terrace where Indigenous People cultivated clams.

Mark Wunsch (Greencoast Media, British Columbia, Canada).

Coastal ecosystems are not only threatened by habitat loss and climate change; a breakdown of traditional aquaculture practices could also have contributed significantly to their deterioration.

This has been illustrated by an 11,500-year analysis of human coexistence with clams in British Columbia, Canada, published in the Proceedings of theNational Academy of Sciences.

Ginevra Toniello, from Simon Fraser University, Canada, and colleagues gathered paleoecological, archaeological and modern records of butter clams(Saxidomus gigantea) in the northern Salish Sea to understand their relationship with humans throughout the Holocene.

The cultural significance of these bivalves is revealed by stories, rituals, language and the deep piles of ancient shell middens that line kilometres of coastlines. Archaeological and ethnographic analyses suggest clams were popular food sources harvested seasonally and all year round and enjoyed both fresh and preserved.

Butter clams from 11,500-11,000 years ago (left) and 10,900-9,500 years ago (right) showing the sometimes dramatic differences in size through time.

Archaeological records can also provide insights into the ecological impacts of interactions between humans and fauna, while palaeoecological information can reveal the ecology of species without human interference.

“Taken together,” Toniello and coauthors write, “these two records can offer a powerful lens through which to assess coupled social-ecological systems over broad spatial and temporal scales and can help establish ecological baselines for modern management.”

To peek into the past, the researchers gathered clam shells from middens at five coastal sites and measured the size and width of growth rings in the mollusc’s shells. They put these into context according to their historical location, before, during and after evidence of management by indigenous people and were able to group the samples into seven time periods.

Together, these data allowed them to analyse predictors of clam size throughout the Holocene.

They found the mollusc shells’ size and growth was limited in early postglacial times, but then flourished over the next few millennia until the early-Late Holocene, likely reflecting more favourable habitat conditions.

Middens showed evidence that humans then harvested them around 9000 years ago, and about 5500 years later started constructing clam gardens – “intertidal rock-walled terraces” – as a form of aquaculture management.

The gardens made the bivalves more accessible to harvesters by reducing the beach slope, exposing more beach during low tide, and bringing them closer to human settlements.

The researchers believe the gardens’ construction reflected population growth and increased complexity of social structures, necessitating measures to preserve the clams for food and trade.

By around 2700 years ago, harvesting intensified, yet evidence suggests the clam populations flourished throughout the Late Holocene.

The clam habitats were likely preserved by the gardens built by generations of Indigenous peoples, the team suggests. Along with cultivation methods such as tilling, removing non-human predators, removing rocks, modifying the substrate and monitoring access, the Indigenous people were able to maintain a sustainable harvest.

Toniello and colleagues speculate that the course sediment garden terrace and rock wall also facilitated abundant growth and access to other marine foods like crabs, sea cucumbers and seaweeds.

Sadly, modern records indicate that growing conditions declined since European settlement replaced traditional management practices with industrial activities, with an impact comparable to the ice age.

“It is striking that the growth patterns of clams living in the beach today are most similar to the clams that lived and died in the unstable and relatively unproductive habitats of the Early Holocene,” the group writes.

“As in the Early Historic Period, we propose that the current low productivity is due to the decline in traditional management, including ongoing tilling through harvesting.”

They note it could also be attributed to deposition of fine silts on the clam beaches – less favourable for clam growth than the coarse grains used as garden substrates – as a result of logging, along with warmer ocean temperatures and associated declines in productivity.

Nonetheless, they suggest modern humans could learn much from traditional practices for aquaculture management, which also has broader ecological and ethical implications.

“Examining the deep and specific history of human-species relationships, such as that between people and clams, is requisite for understanding and better managing our resources and ecosystems today,” they write.

“Documenting these interactions between humans and coastal ecosystems, such as we have done here, also counteracts the erasure of the long-term connections of Indigenous peoples to their lands and seas.”

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