First Australians: How Humans Reached Australia by Sea

The peopling of Australia was the arrival of the first humans in Sahul, the Ice Age continent that joined Australia, New Guinea and Tasmania, roughly 65,000 to 50,000 years ago. To get there, the ancestors of today’s Aboriginal Australians and Papuans had to cross a chain of islands separated by open sea, making these the earliest known long sea voyages in human history. Their descendants went on to settle the whole continent, from tropical coasts to the deserts and the cold south of Tasmania, and maintained cultures that have continued for tens of thousands of years.

Background: Sunda, Sahul and Wallacea

During the Ice Ages, much of the world’s water was locked in ice sheets and sea levels were up to about 120 metres lower than today. The shallow seas of western Indonesia became dry land, forming Sunda, an extension of mainland South-East Asia that included Sumatra, Java and Borneo. To the south-east, Australia, New Guinea and Tasmania formed a single continent, Sahul.

Between them lay Wallacea, a scatter of islands including Sulawesi, Timor, Flores and the Moluccas. These islands sit in deep water and were never joined to either continent. The boundary is marked by the Wallace Line, named after the 19th-century naturalist Alfred Russel Wallace, who noticed the sharp difference between Asian and Australian animals on either side.

Anyone travelling from Asia to Sahul, even at the lowest sea levels, had to make several crossings. Some gaps were short enough for land on the far side to be visible, but at least one was probably around 70 kilometres or more. Earlier hominins had reached some Wallacean islands, such as Flores, but there is no evidence that any human species before Homo sapiens reached Sahul.

Who the first Australians were

The first Australians were modern humans, part of the wider dispersal of Homo sapiens from Africa (see Out of Africa). Genetic studies of Aboriginal Australians and Papuans, including a 2011 genome sequenced from a century-old hair sample and a larger 2016 study, show that their ancestors separated from the ancestors of other Asians early, and that they descend from a single founding population with no sign of later replacement.

Like other non-Africans, Aboriginal Australians and Papuans carry a small share of Neanderthal DNA. They also carry several percent of Denisovan DNA, among the highest levels in the world, suggesting that their ancestors met Denisovans somewhere in South-East Asia or Wallacea on the way.

Many Aboriginal communities hold, through their own traditions, that their peoples have always been in Australia, with the land and its law created in the Dreaming. Archaeologists working with these communities increasingly treat this deep connection to Country as a framework alongside scientific dating rather than in competition with it. At sites such as Madjedbebe, excavations have been carried out in partnership with the Traditional Owners, who hold authority over the site and its interpretation.

The sea crossings

No boats or rafts survive from this period, so how people crossed is inferred. Most researchers think they used rafts or simple watercraft, perhaps made of bamboo, which grows widely in the region. The number of crossings, the distances and the need to bring enough people to found a lasting population all suggest that at least some voyages were planned rather than accidental drifts.

Two main routes have been proposed:

• The northern route ran from Borneo through Sulawesi and the Moluccas to New Guinea, the western part of Sahul.
• The southern route ran from Java through the Lesser Sunda Islands, including Flores and Timor, to the now-drowned continental shelf off north-western Australia.

Studies modelling which islands were visible from which suggest the northern route offered more chances to see the next landfall, but both routes may have been used at different times. A 2019 modelling study estimated that a population of at least roughly 1,300 people was needed to establish a lasting presence, implying repeated or organised arrivals.

Dating the arrival

When people first arrived is one of the most debated questions in Australian archaeology.

For decades, the widely cited figure was about 40,000 years ago, based on radiocarbon dating, which cannot reliably date anything much older than about 50,000 years. Luminescence dating, which measures when sand grains were last exposed to sunlight, has since pushed dates further back.

The strongest claim for an early arrival comes from Madjedbebe, a rock shelter in Arnhem Land in the Northern Territory. In 2017 a team led by Chris Clarkson reported stone tools, ground ochre and early ground-edge axes there dated to about 65,000 years ago. Critics argue that artefacts may have moved down through the sandy deposits and that genetic estimates fit better with arrival around 50,000 to 45,000 years ago.

Several other sites, such as Boodie Cave on Barrow Island and Warratyi rock shelter in the Flinders Ranges of South Australia, have been dated to around 50,000 years ago. In the New Guinea highlands, people were using stone tools in the Ivane Valley about 49,000 to 43,000 years ago. Most researchers therefore accept that humans were in Sahul by at least 50,000 years ago, and some are confident of an earlier date.

Genetics offers an independent clock, but an imprecise one. Estimates of when the ancestors of Aboriginal Australians and Papuans split from other populations depend on assumed mutation rates and generation lengths, and they generally fall somewhere between about 70,000 and 50,000 years ago. The ancestors of Aboriginal Australians and Papuans themselves appear to have separated within Sahul, long before rising seas divided New Guinea from Australia. Resolving the arrival date will probably need more excavated sites with secure dating, especially on the drowned continental shelf, where the earliest coastal camps now lie under the sea.

Settling a continent

Once in Sahul, people spread across a continent with very varied environments. At Lake Mungo in western New South Wales, the burials known as Mungo Lady and Mungo Man, discovered in 1968 and 1974 by teams including the geologist Jim Bowler, date to roughly 40,000 years ago and include the world’s oldest known cremation. Tasmania, then joined to the mainland, was occupied by at least about 39,000 years ago, and the archaeologist Rhys Jones showed that people there lived through the coldest periods of the last Ice Age.

People adapted to tropical forests, coasts, highlands, river systems and deserts. They used fire to manage landscapes, made ground-edge stone axes far earlier than people in Europe, and developed trade networks over long distances. Ochre, shell ornaments and rock art appear early; the oldest dated rock painting in Australia, a kangaroo in the Kimberley region, is about 17,300 years old.

Impact on the environment

The arrival of people coincided broadly with the disappearance of much of Australia’s megafauna, giant animals such as Diprotodon, the marsupial lion and giant flightless birds. Many of these species vanished around 46,000 to 40,000 years ago. Whether hunting, landscape burning, climate change or a combination caused the extinctions is still debated.

Rising seas and separation

At the end of the last Ice Age, rising seas divided Sahul. Tasmania was cut off by the flooding of Bass Strait around 12,000 to 10,000 years ago, and New Guinea was separated from Australia when the Torres Strait flooded, around 8,000 years ago. Aboriginal oral traditions in several regions describe coastlines being drowned, and some scholars argue these stories may preserve memories of this sea-level rise, though this is difficult to test.

The dingo arrived much later, about 3,500 years ago or more, probably with seafarers from South-East Asia. Otherwise, Aboriginal Australia developed largely independently until the arrival of Europeans in the 17th and 18th centuries.

Myths and facts

• Myth: Aboriginal Australians arrived a few thousand years ago. Archaeology and genetics show their ancestors arrived at least 50,000 years ago.
• Myth: people walked to Australia over a land bridge. There was never a continuous land connection from Asia to Sahul; sea crossings were always needed.
• Fact: the date is genuinely uncertain. The range of about 65,000 to 50,000 years reflects real scientific disagreement, not a lack of research.

By the numbers

Timeline

• c. 65,000 years ago: Disputed earliest evidence of people at Madjedbebe, Arnhem Land.
• c. 50,000 years ago: People present at several sites across Sahul.
• c. 49,000-43,000 years ago: Stone tools in the New Guinea highlands.
• c. 46,000-40,000 years ago: Many megafauna species disappear.
• c. 42,000-40,000 years ago: Burials of Mungo Lady and Mungo Man.
• c. 39,000 years ago: People living in Tasmania.
• c. 12,000-10,000 years ago: Rising seas cut Tasmania off from the mainland.
• c. 8,000 years ago: Torres Strait floods, separating New Guinea from Australia.
• 2017: Madjedbebe dates of about 65,000 years are published.

Why it matters

The peopling of Australia is the earliest clear evidence of humans deliberately crossing the sea and colonising a new continent. It shows the planning, technology and adaptability of early modern humans, and it underpins the deep history of Aboriginal and Torres Strait Islander peoples, whose cultures connect today’s Australia to its first arrivals.