Wide, parabolic bays like this stretch between rocky headlands in the southern end of the study area. View south from North Head towards Jurien Bay.
Looking out over the glittering turquoise bays and limestone ledges of Western Australia’s ‘Coral Coast’, it can be easy to forget that the coastline we see today only began to resemble its modern form about 6,000 years ago. Marine gastropods like turban snails, abalone, and limpets established themselves in littoral ecosystems, producing a rich range of food sources that were readily accessible to Aboriginal people wading through the intertidal zone. For several thousand years, people on the Mid West coast exploited these resources, leaving evidence in the form of middens: culturally-derived scatters of shell, bone and stone tools. But around 3,000 years ago, midden formation appears to have stopped abruptly. Why?
In a paper published this week in Australian Archaeology, Bob Sheppard, Joe Dortch and I report the findings of the investigation of two new midden sites on the Mid West coast: the first at Oakajee River, north of Geraldton, and the second at North Head, near Jurien Bay. Radiocarbon dating shows that these sites are between 4,500 and 5,600 years old, with both middens apparently forming over a very short period of time. Possibly best described as small, shallow shell scatters, the Oakajee and North Head middens are typical of midden sites in the Mid West. They add to a growing body of evidence which suggests that through the mid-Holocene, Aboriginal people living along the coast engaged in consistent (though small-scale) exploitation of coastal ecosystems, including littoral and estuarine resources.
Some of the shells from an eroded section of the North Head midden, including turban snails, chitons, abalone, and limpets.
The sites also add to the evidence of regular use of littoral resources prior to 3,000 years ago, when an environmental or cultural change apparently resulted in these resources became far less economically important. Research carried out in the 1980s indicated that the decline in intertidal foraging could have been related to changes in marine and estuarine coastal formation processes that changed the availability of many mollusc species. Changes to the highly productive hind-dune lagoons occurring together with these processes would have altered the ways in which Aboriginal groups used the coastal fringe. As a result, fish and terrestrial species became the primary focus of coastal economies in the region, with molluscs only exploited in very small quantities (Dortch 1997; Hallam 1987).
Interestingly, geomorphological research (which looks at the formation and evolution of surface landforms and landscapes, including coastlines) suggests that the Mid West coastline may have experienced increased storm activity in the mid- to late Holocene. This storm activity would have included higher energy waves and storm surges, and is supported by evidence of a period of increased erosion of coastal sand dunes around 3,000 to 2,000 years ago. Could this have been the driving factor behind this regional change?
Map of the lower Mid West, showing the locations of all dated archaeological shell middens. Image source.
It seems likely that increased storm and erosional activity could have trigged changes to the environmentally sensitive littoral and estuarine ecosystems. Certainly, there is good reason to think that changing coastal conditions made these resources less reliable, and that this may have altered the way that Aboriginal people were using coastal and inland landscapes. For parts of the coastal plain further south (towards Perth), Hallam argued that it was the coastal woodland, riverine and wetland communities that were the cornerstone of the mid- to late Holocene economy. But what about the coastal plain north of Jurien Bay, which is dotted with salt lakes instead of freshwater wetlands, and is covered in more arid-adapted kwongan and woodland vegetation?
As part of my PhD research, I’m interested in seeing how inland resources – including animals like kangaroos, small mammals, and emus – were being used at that time. Was there a corresponding change in food sources in other sites across the coastal plain, as marine resources became less important?
You can help with this research!
To understand the ways in which Aboriginal people living in the Mid West and Swan coastal plains dealt with changes like this, we’re currently investigating several sites further inland. Limestone caves like those found near Jurien Bay and Leeman contain well-preserved archaeological and palaeontological evidence that can help us understand Aboriginal cultural practices and environmental conditions. We are currently raising funds to do fieldwork later this year, and every donation (be it $5 or $500) will help get us closer to understanding the complex relationships between Aboriginal people and the plants and animals of coastal plains. Please visit our fundraising page to learn more about this research.
This post is based on research published in Australian Archaeology, vol. 80:
archaeoecology 