Getting to Australia was never a matter of walking. Even at the lowest sea levels of the ice age, the continent — then joined with New Guinea as a landmass called Sahul — was cut off by open ocean. Whoever got there first had to cross the sea on purpose, in something that floated, with enough people aboard to found a population. For years the textbooks put that crossing at 47,000 to 50,000 years ago, which was impressive enough.
A rock shelter called Madjedbebe, on Mirarr Country in Arnhem Land near Kakadu, says it happened considerably earlier.
Madjedbebe was re-excavated in 2012 and 2015 by a team led by Chris Clarkson, working with the Mirarr Traditional Owners. Through about two and a half metres of deposit they recovered more than 10,000 artifacts: ground-edge axes — among the oldest in the world — seed-grinding stones, finely made points, and the residues of ochre and mica pigment processing. People weren’t just passing through; they were cooking, grinding, painting, and making tools at the edge of the world.
The chronology is the strong part. Clarkson and colleagues, publishing in Nature in 2017, built it on single-grain optically stimulated luminescence — 52 samples, some 25,700 individual quartz grains, each grain reporting when it last saw sunlight — checked against radiocarbon where the two methods overlap. The first dense band of occupation dates to 65,000 years ago, give or take about 6,000.
The criticism, because there is one and it deserves naming: Jim Allen and James O’Connell have argued that in a sandy deposit worked by termites and roots, artifacts can migrate downward, so the link between the deepest tools and the 65,000-year-old sand is the thing to defend. The excavation team answers that the density bands and the grain-age distributions rule it out. Most archaeologists now work with roughly 65,000 years; a minority holds out. Say both, and the date still stands as the majority reading.
Which leaves the quiet bombshell inside the number. Sixty-five thousand years ago — some fifteen thousand years earlier than the old story allowed — somebody’s ancestors built watercraft, crossed open ocean they could not see across, and made a new continent home. Boats before farming, before pottery, before almost everything. Tomorrow, the last in this series: the oldest story ever told in pictures.
Read more: Clarkson et al. 2017, Nature (https://doi.org/10.1038/nature22968); HeritageDaily’s report on the find (https://www.heritagedaily.com/2017/07/kakadu-find-confirms-earliest-australian-occupation/116001).