The project had two main starting points: mapping palaeocoastlines and using archaeogenetics to analyse population movement and migration timing. Both investigations provided parameters for palaeohydrodynamic modelling to understand early seafaring.
The archaeogenetics working group looked at population movement through the region. Analysing a substantial new data set that improved molecular clock estimates and enlarged the phylogenetic tree. The data included 13,811 genome-wide SNPs for 1671 individuals from 100 locations, and 23,121 genome-wide SNPs for 1204 individuals from 71 locations. The analysis of 176 new whole genome also proved invaluable for the genetic dating of settlement chronologies. Alongside the mtDNA data, this allowed for further precision on the chronology of the first settlement of Sahul, supporting the long chronology for movement into the region and known radiometric dates of ca. 60,000ka. A Y-chromosome tree from the Sahulian SNP data was also generated.
The palaeolandscape and sea-level analysis within this research underpinned the reconstructions of the palaeomarine and coastal environments and provided the project with parameters for analysing seafaring routes, technology and skill. Global changes in relative sea-level have had a profound effect on the movement of people, and on our existing archaeological archive. A considerable proportion of the palaeo record has been submerged during the last postglacial marine transgression. Two million km2 of potentially inhabitable land on the Sahul shelf is now submerged.
Using offshore industry data and seismic analysis, ACROSS reconstructed the region’s changing coastal landscape. The analysis of sea-level curves, offshore cores, and recalibrated dates helped refine sea-level models for MIS2–MIS6, locating the palaeocoast during MIS4 when maritime movements into Sahul likely began. Local environmental markers, such as reefs and estuaries, were identified, aiding the understanding of the monsoon system and the changing landscape. These results also suggest submerged cultural sites could be preserved.
ACROSS ran models to explore ocean currents, tides, and winds to study early voyages. The models revealed likely successful routes, time at sea, and chances of success. The monsoon system was crucial to these voyages, showing that accidental drifting was unlikely, and some form of propulsion was likely used. This indicated a basic level of seafaring skill and knowledge of the marine environment.
This work integrated onshore and offshore narratives, moving discussion beyond the environmental domain to re-focus on the human past and human narratives of activity. The interweaving of archaeology, marine science and cultural heritage allows us to discuss the ‘Human Ocean’, where people’s activity and narratives, both create Sea Country, and adapt to its changes.
Through studying these land and seascapes, we improve our understanding of a range of themes from sea-level rise and climate change to ecology and hydrology of the landscape, to past activity, and lived and remembered landscapes through time. When the continental shelf is also recognised as representing a complex hermeneutic landscape, entwining multiple narratives and layers of significant space, its continued cultural importance to community today can also be perceived.
In Australia, where maritime activity can be traced back to the Late Pleistocene oral traditions have deep roots. Multiple Indigenous stories along the northern Australian coast talk of origins, seafaring, voyages, and the coastal environments encountered and created. These narratives reflect the deep heritage of coastal activity and seafaring, which supports discussion of maritime cultural heritage, encounter and arrival through time.
By giving shape to these land and seascapes, ACROSS recognises the deep heritage of the region and the now-submerged continental shelves, which form a part of traditional Country and Sea Country: travelled, active, cultural landscapes for Indigenous community today.
The project has presented and published a range of scientific papers on these themes, and produced a podcast series, webpage and other media projects to share these methods, results and narratives.
