Shimona KealySome 4,200 years ago, people started to leave what is now Taiwan to migrate to the thousands of islands to the south, spanning as far west as Madagascar in the western Indian Ocean and as far east as Rapa Nui (Easter Island) in the eastern Pacific Ocean.We can trace this migration through the way language spread, creating the largest-scale language dispersal in prehistory.But what exactly drove these people to make these distant and dangerous voyages? Our discovery of a 4,000-year-old painting of a sunburst in southeastern Indonesia offers some clues. This painting of a sunburst may explain why ancient people in Taiwan sailed thousands of kilometres into the unknown. Shimona Kealy A charismatic cultural identityAustronesian is a close-knit language family spoken across much of Malaysia, the Philippines, Indonesia, Madagascar and the Pacific Islands. Some of the major languages in this family include Malay, Javanese, Sundanese, Tagalog, Cebuano and Malagasy.We know the Austronesian migration began at least around 4,200 years ago, as this is when characteristic Austronesian red pottery and rectangular stone adzes (axe-like tools) appear on islands south of Taiwan. The extraordinary seafaring abilities of Austronesians were underpinned by the outrigger canoe, but it is unclear which other factors propelled their expansion.Previous models have suggested advancements in rice farming and storage (thanks to pottery) might have fuelled population growth, prompting the Austronesian people to migrate to neighbouring islands for new farmland. However, rice and pottery are not universal features of Austronesian societies. An alternative theory is that there was a powerful and charismatic cultural identity shared by the Austronesian people – the kind that attracted outsiders and encouraged daring voyages to remote uninhabited islands.Discoveries from WetarFinding archaeological evidence for the presence of a past cultural identity is difficult, but rock art does provide a way.In the 1992 book State of the Art, Australian anthropologist Chris Ballard observed there was a style of red rock paintings found mainly in areas where Austronesian is spoken today – eastern Indonesia, Timor and coastal New Guinea – but not in neighbouring parts of these islands where Papuan languages are spoken. Ballard named this style of painting the Austronesian Painting Tradition (APT). It was characterised by motifs of small human figures, often wielding weapons or on boats, as well as a geometric sun ray of concentric circles with radiating spokes.The age of this painting tradition has long remained a mystery, however, because of how difficult it is to date art painted on walls. In 2023, we carried out the first ever archaeological investigation on the island of Wetar in southeastern Indonesia, with colleagues from the Indonesian National Research and Innovation Agency. During this survey we identified a large rock overhang called Huknaur, with APT art on its walls. We excavated the site in 2024 and were lucky enough to find a stone plaque painted with the characteristic APT sun ray motif, in a layer radiocarbon dated to 4,000 years ago. The painting on the plaque (scale bar 5cm). False-colour images show different shades (now faded) that were used to paint more concentric circles and radiating spokes. Shimona Kealy This symbol matches designs documented on cliff walls across the APT region, such as in the Philippines, Timor-Leste and southeastern Indonesia.Historical documents show these sun ray symbols were also applied to boat prows in the region, both to protect voyagers and as clan identity markers.This iconography may have been part of a broader shared symbolic culture that helped maintain Austronesian identity and kept communities connected across thousands of kilometres of ocean. A compilation of concentric circle motifs from the APT repertoire. Top row: Peñablanca area (Philippines), Ile Kere Kere (Timor-Leste), Ile Kere Kere (Timor-Leste), Intutun 6 (Kisar). Row 2: Inuntun 4 (Kisar), Inuntun 4 (Kisar), Jawalang 4 (Kisar). Row 3: Jawalang 4 (Kisar), Jawalang 4 (Kisar), Jawalang 4 (Kisar), Raitawuni 2 (Wetang). Row 4: Huknaur 2 (Wetar), Huknaur 1 (Wetar), Huknaur 1 (Wetar), Huknaur 1 (Wetar). Shimona Kealy Our excavation also found the earliest Austronesian pottery at Huknaur is dated to about 3,500 years ago – some 500 years after the sun ray plaque was painted. This suggests Austronesian pioneers may have arrived with their compelling cultural identity, represented by the paintings, before later Austronesian arrivals brought pottery. Before the Austronesian arrivalThe Huknaur site was not uninhabited prior to Austronesian contact. As far back as 9,500 years ago, this site had been the centre of a network moving obsidian (the sharpest material used to make stone tools) from Wetar to at least four other islands in the region. Before the time of the sun ray plaque, people at the site adorned themselves with beads made of whole Oliva shells and small discs of shiny Nautilus shell. These were replaced with domes and discs of Conus shell around the time the plaque was painted.Conus beads have also been found at other early Austronesian sites. So the examples from Huknaur provide independent evidence for the arrival of the Austronesian people, along with their belief system. Bead types from Huknaur (scale bar 1cm), including water-worn Conus spires (A), ground Conus discs (B), nautilus discs (C), Oliva shells (D), as well as a glass bead from the most recent occupation of the site (E). Ceri Shipton An ambitious seafaring peoplesIf the Huknaur sun ray plaque represents the arrival of Austronesian pioneers, as we suspect it does, its 4,000-year age makes it one of the earliest places outside Taiwan to document the Austronesian migration. Our findings suggest Austronesia explorers may have leapfrogged to centres of influence, rather than simply advancing to the next nearest island. We know Spanish conquistadors travelled about 3,500km from Hispaniola to the Inca capital of Cuzco in just 40 years, which is roughly the same distance as the voyage from Taiwan to Wetar. And they did so without occupying every region in between. The APT painted plaque at Huknaur prompts us look beyond technology and economy as drivers of prehistoric human expansion. Ideology and ambition – as much as they are harder to find evidence for – were equally important drivers.Ceri Shipton receives funding from the Australian Research Council. Shimona Kealy received funding from the Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage (CE170100015) and ARC Discovery Project (DP240100747).Sue O'Connor receives funding from the Australian Research Council ARC Discovery Project (DP240100747).