Ancient Sea Rise Submerged Hunter-Gatherer Lands Beneath the Northern Adriatic

Beneath the shallow waters of the Adriatic Sea, off the coasts of northern Italy, Slovenia and northern Croatia, lies a drowned world that archaeologists have long struggled to reach. A new study led by the University of Southampton in the United Kingdom, together with the National Institute of Oceanography and Applied Geophysics (OGS) in Italy, has reconstructed in unprecedented detail how dramatic sea level rise over a 5,000-year period profoundly reshaped the coasts of the Northern Adriatic, transforming vast plains into wetlands, lagoons and eventually the shoreline visible today. The research, published in the journal Quaternary Science Reviews, reconstructs the evolution of the regional landscape between roughly 9,000 and 4,000 BC, a window of time that spans the transition from Mesolithic hunter-gatherer societies to Neolithic farming communities.

The central finding is staggering in its implications for how prehistoric life is understood in the region. Land once roamed by hunter-gatherers and later tended by early farmers now lies deep beneath the sea. The present-day Venice Lagoon, famous for its island city built on marshy, muddy ground, was once dry land that lay kilometres from the coast. The same is true of other towns in the lagoons further east, such as Grado, and even present-day coastal cities like Trieste would once have stood in hills overlooking swamps and lagoons below. In other words, some of the most archaeologically significant terrain in the region is invisible to conventional, land-based survey, hidden beneath seabed sediments that have accumulated over millennia.

Technically, the study is a palaeolandscape reconstruction built from two complementary strands of evidence. The researchers combined existing data from the analysis of sediment cores with new, high-resolution geophysical data acquired by OGS. Sediment cores allow scientists to identify different types of deposits, each characteristic of a particular environment, whether open marine, coastal barrier, lagoon, marsh or floodplain. Geophysical surveys, in turn, reveal the buried architecture of these deposits across wide areas of the seabed. By identifying the sediment types and modelling successive flooding episodes, the team was able to trace the backward shifting of coastal barriers, deposits running parallel to the shore, and the back-barrier systems, the marshy areas that lay beyond them. The result is a sequence of maps showing how the coastline retreated inland, stage by stage, across five millennia.

The timeline that emerges is anything but smooth. The reconstruction identifies a rapid rise in sea level around 8,400 BC that created tidal channels, marshes, sandbanks and large lagoons, followed by a more stable phase in which these features could persist and develop. Then came a large rise, a total of eight metres in the 1,200 years leading up to 6,600 BC, during which the sea repeatedly created, subsumed and recreated lagoons and marshes, pushing kilometres inland. A further major rise of up to five metres after 6,000 BC again shifted coastal features landward. Finally, after about 5,800 BC, the origins of the lagoons and the landscape recognisable today began to form. At times, the rate of rise reached up to 25 millimetres per year, a pace that would have been plainly visible within a single human lifetime.

That pace matters for understanding what prehistoric communities actually experienced. A rise of 25 millimetres per year translates into roughly a metre of relative sea level change across two or three generations, enough to permanently abandon settlements, alter hunting grounds and redraw the geography of trade and movement. The study highlights the constantly changing environment that Mesolithic hunter-gatherers had to cope with, as rising water altered habitats, resources and the availability of food such as plants, fish and animal prey. Coastal barriers were overrun and rebuilt; lagoons formed, filled and re-formed. Successive shaping and reshaping of coastal features influenced the lives of Mesolithic and Neolithic people and the development of local communities, as the sea swallowed features it had previously formed, shaped new ones, and eventually produced the origins of the modern coast.

Samuele Ongaro, lead author and PhD researcher at the University of Southampton, an archaeologist by training, emphasises why these drowned terrains matter. Submerged landscapes, he notes, are an important missing piece in the study of prehistory, especially in the Northern Adriatic, because they hold many secrets about how ancestors lived and how they were connected to the land. According to Ongaro, the results of the research allow the reconstruction of these lost landscapes, the environments they hosted, how they changed over time, and what significance they might have held for prehistoric populations, which he describes as a fundamental step for future archaeological research in the area. The framing is significant: rather than treating the seabed as a blank between terrestrial sites, the study treats it as a continuous, inhabited landscape worthy of systematic investigation.

The environmental variety of the reconstructed coast also helps explain why people were drawn to it in the first place. As Ongaro points out, the variety of coastal environments, lagoons, river deltas, marshes and swamps, would have been an attractive landscape for foragers and hunters, offering diverse and productive ecological niches. Yet the flat nature of the landscape also made it prone to significant land loss, and communities were forced to adapt over time, choosing where to hunt, fish and settle. This tension, between ecological richness and geographic vulnerability, is central to the study’s archaeological implications. The team hopes further study will reveal more about how communities shifted their activities in response to coastal flooding, and how this eventually affected the advent of farming in the region by Neolithic people, one of the most debated transitions in European prehistory.

From the marine geoscience side, the collaboration demonstrates the value of integrating geological and geophysical data. Dr Federica Donda, a marine geologist from the Geophysics section of OGS and co-author of the paper, comments that the study shows how integrating geological and geophysical data makes it possible to reconstruct the environmental evolution of areas that are now submerged, while highlighting that the seabed is an integral part of archaeological heritage. In her view, a significant portion of the areas frequented by ancient populations is now underwater, and their history and evolution cannot be understood through terrestrial archaeology alone. This is a pointed methodological claim: any model of Mesolithic or Neolithic settlement in the Northern Adriatic that ignores the drowned plains is, by definition, incomplete, because it excludes the very terrain where much of early coastal life unfolded.

The paper, titled Palaeolandscape reconstructions for the Northern Adriatic: Inundation models, depositional environments, and potential archaeological implications, underscores the potential of palaeogeographic reconstructions for studying the evolution of past societies. By returning to archaeological research a piece of territory that is no longer visible today, but which for thousands of years was part of the European landscape, the work opens a path toward predictive models of where submerged prehistoric sites might survive. The method of research is described as computational simulation and modelling, combining inundation models with depositional interpretations, an approach that could be applied to other drowned coastlines around the world where post-glacial sea level rise has erased the record of early coastal adaptation.

For a region whose modern identity is bound up with the fragile balance between water and land, from the Venice Lagoon to the gravelly shores of Trieste, the study offers a deep-time perspective on an ongoing process. The coast that residents and visitors know today is merely the latest configuration in a long sequence of flooding, barrier migration and lagoon formation that began when the last ice age ended. What the Southampton and OGS team has shown is that this sequence is readable in the sediments beneath the seabed, and that within those sediments lie clues to how some of Europe’s earliest coastal communities lived, moved and adapted as the sea rose around them. The next stage of research, the authors suggest, will focus on pinning down how human activity responded to each successive inundation, turning a drowned landscape into a map of prehistoric resilience.

Subject of Research: Prehistoric sea level rise and coastal landscape change in the Northern Adriatic

Article Title: Study reveals how prehistoric coastal flooding shaped the Northern Adriatic

Article References: Study reveals how prehistoric coastal flooding shaped the Northern Adriatic. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Northern Adriatic, sea level rise, Venice Lagoon, Mesolithic, Neolithic, submerged landscapes, palaeogeography, coastal barriers, lagoons, sediment cores, geophysics, Quaternary Science Reviews