Skip to main content

Rising sea levels destroyed evidence of shell middens at many prehistoric coastal sites

Archaeological remains of coastal occupation in the form of shell middens are commonly found on today's shorelines, and evidence for shellfish as a food source goes back 164,000 years. Within this time frame, sea-levels changed dramatically and shorelines moved on the scale of kilometers. The current study, published in PLOS ONE, reveals that this movement of coastlines impacted the majority of shell middens by causing shells to wash away or to currently be underwater, and thus has skewed our understanding of past coastal subsistence around the world.
Shells as food waste are a common find in archaeological coastal sites of the last 164,000 years -- but many may now be hidden from view.
In this study, an international team of researchers quantified patterns that were first described by Australian archaeologist and anthropologist Betty Meehan in the 1970s. Meehan described how modern-day coastal foragers of the Australian coast processed most of their shellfish on the direct shoreline to decrease transport weight and only carried some shells that still contained meat further inland to their main habitation site to be processed there. The researchers theorized that if prehistoric people at a particular site used the same strategy, and if sea-levels rose dramatically since that time, archaeologists today would no longer find evidence of large shell middens related to that population. If only a few shells were found close to the habitation site, researchers might assume that the population did not rely heavily on shellfish for subsistence -- and this would of course be incorrect.
Using a large cluster of over 3,000 prehistoric shell midden sites on the Farasan Islands in the Arabian Red Sea, the researchers assessed their spatial and temporal patterns in the context of long-term sea-level change. A selection of sites was radiocarbon dated to 7,500 to 4,700 years ago. During this period, the sea-level of the southern Red Sea was still rising as a result of melting glaciers at the end of the last Ice Age. The rise came to a stop around 6,000 years ago and the sea level was slightly higher (2-3 m) than today. This was followed by a gradual drop over ~2,000 years to our current sea levels, excepting the rise of recent decades.
Coastal exploitation of shellfish changed little during this period, and rates of shell accumulation based on radiocarbon dates indicate that 10 times more shells were deposited at the direct shoreline than at 'post-shore' locations, mirroring Meehan's ethnological research. However, despite their larger size, no shore-line sites are preserved that date to before 6,000 years ago, closely following the sea-level change in this region and pointing toward a large number of sites that must have been lost to the sea since the beginning of coastal subsistence.
Usually well preserved at archaeological sites, shells are easily washed away by rising sea levels.
"We already knew that coastal sites are in a precarious situation and we often rely on sites along steep cliffs or a few hundred meters inland to study the collection of shellfish dating to before today's sea-levels," explains first author Niklas Hausmann of the Max Planck Institute for the Science of Human History. "Now we know that not only a little bit was left at the beach, but the bulk of the shell material, which really undermines our idea of how much shellfish was eaten at sites even slightly inland."
"With our study, we have shown that a lot more shellfish meat was eaten in times of lower sea-levels than we previously thought, and we have to get away from the simplified 'shell equals shellfish meat' attitude," explains Hausmann.
Shellfish are often over-represented in the assessment of past coastal subsistence due to their hard shells preserving better than plants or even bones. However, the meat they contain is archaeologically invisible and could have been eaten anywhere. This study shows that the potential use of beach-side processing sites connected to habitational areas cannot be discounted, especially when such coastal processing sites may now be under water.
Story Source:
Note: Content may be edited.

Comments

Post a Comment

Popular posts from this blog

Size matters: New data reveals cell size sparks genome awakening in embryos

Transitions are a hallmark of life. When dormant plants flower in the spring or when a young adult strikes out on their own, there is a shift in control. Similarly, there is a transition during early development when an embryo undergoes biochemical changes, switching from being controlled by maternal molecules to being governed by its own genome. For the first time, a team from the Perelman School of Medicine at the University of Pennsylvania found in an embryo that activation of its genome does not happen all at once, instead it follows a specific pattern controlled primarily by the various sizes of its cells. The researchers published their results this week as the cover story in  Developmental Cell . In an early embryo undergoing cell division, maternally loaded RNA and proteins regulate the cell cycle. The genomes of the zygote -- a term for the fertilized egg -- are initially in sleep mode. However, at a point in the early life of the embryo, these zygotic nuclei "wake...
Post a Comment
Read more

Home births as safe as hospital births: International study suggests

A large international study led by McMaster University shows that low risk pregnant women who intend to give birth at home have no increased chance of the baby's perinatal or neonatal death compared to other low risk women who intend to give birth in a hospital. The results have been published by  The Lancet 's  EClinicalMedicine  journal. "More women in well-resourced countries are choosing birth at home, but concerns have persisted about their safety," said Eileen Hutton, professor emeritus of obstetrics and gynecology at McMaster, founding director of the McMaster Midwifery Research Centre and first author of the paper. "This research clearly demonstrates the risk is no different when the birth is intended to be at home or in hospital." The study examined the safety of place of birth by reporting on the risk of death at the time of birth or within the first four weeks, and found no clinically important or statistically different risk between home...
Post a Comment
Read more

Molecular adlayer produced by dissolving water-insoluble nanographene in water

Molecular adlayer produced by dissolving water-insoluble nanographene in water : "Nanographene incorporated micelle capsules" can be prepared by simply pulverizing and mixing nanographene with amphiphilic V-shaped anthracene molecules in water at room temperature. Even though nanographene is insoluble in water and organic solvents, Kumamoto University (KU) and Tokyo Institute of Technology (Tokyo Tech) researchers have found a way to dissolve it in water. Using "molecular containers" that encapsulate water-insoluble molecules, the researchers developed a formation procedure for a nanographene adlayer, a layer that chemically interacts with the underlying substance, by just mixing the molecular containers and nanographene together in water. The method is expected to be useful for the fabrication and analysis of next-generation functional nanomaterials. Graphene is a single layer of carbon atoms arranged in sheet form. It is lighter than metal wit...
Post a Comment
Read more