How much shellfish did ancient coastal societies actually eat?

Published online 26 June 2019

Archaeological shell mounds on southern Red Sea islands provide evidence that pre-historic coastal societies probably ate more shellfish than we thought.

Felaniaina Rakotondradany

Inland site showing scattered mollusk shells.
Inland site showing scattered mollusk shells.
© 2019 Hausmann et al
Data extracted from archaeological shell mounds on a Red Sea island provides evidence that similar sites were probably washed away by rising sea levels thousands of years ago. The findings suggest we could be underestimating how dependent prehistoric coastal societies were on shellfish as a food source. 

Researchers in Germany, the UK, and Australia analysed the contents of shell mounds present on Farasan Kabir Island, the largest in an archipelago of Saudi Arabian coral islands present in the southern Red Sea. The islands uniquely combine remoteness, a sparse population, and a dry climate, leading to a plethora of well-preserved archaeological sites, says La Trobe University archaeologist Matthew Meredith-Williams. Shell middens are sites where marine animals were removed from their shells for consumption. More than 3,000 shell middens had previously been identified in the Farasan Islands.

Samples were taken from various depths in each of 15 mounds chosen for radiocarbon dating. The team also analysed the types of marine shells and other content present in the mounds.

Scientists already knew that sea levels were highest in this area around 6,000 years ago; two meters above today’s levels with a shoreline a few hundred meters further inland. The researchers discovered that the oldest shell middens from among those tested were around 7,300 years old and were located inland in what they refer to as ‘post-shore’ sites, most likely located close to places of habitation. Shells accumulated at a slower rate at these shell middens than they did at those closer to the ancient shoreline. The most recent shell middens were about 4,700 years old. 

Shell mound comprising multiple mollusk shell layers.
Shell mound comprising multiple mollusk shell layers.
© 2019 Hausmann et al.
Taken together, the findings provide evidence that ancient humans living on the island removed much of the meat from the shells near the shoreline and only carried some intact shellfish closer to where they lived for processing. The researchers also demonstrated that shellfish exploitation was a year-round activity in the region, “dispelling the preconceived idea that this activity was highly seasonal,” says archaeologist Niklas Hausmann from the Max-Planck Institute for the Science of Human History, Germany. 

The older post-shore sites located close to places of habitation would have been saved from rising sea levels that happened up to a time 6,000 years ago. Shell processing sites located at the ancient shorelines were all dated to less than 6,000 years, suggesting that earlier sites could have existed but were wiped away by rising sea levels.

“These results suggest that we are actually missing a far more significant portion of this record than initially apparent, and should make clear that losing heritage sites due to sea level changes is not a singular occurrence but guaranteed to happen globally,” says geoarchaeologist Robyn Inglis from Macquarie University, Australia. 

Investigations are already underway in some parts of the world to study submerged shell midden deposits using underwater techniques. “The search for the missing palaeoshorelines of the Last Glacial period and their associated coastal sites remains one of the great challenges for the future,” conclude the researchers in their study published in the journal PLOS One.


Hausmann, N. et al. Quantifying spatial variability in shell midden formation in the Farasan Islands, Saudi Arabia. PLoS ONE 14, e0217596 (2019).