Regular crossings
It is obvious that present day Australian Aborigines are the descendants of the people who first populated parts of Asia; in particular from the lands that incorporate the islands of present day Indonesia. But when were the first crossings made; and do they and the people who now occupy SE Asia have ancestors in common?
Regular crossings happen, even at present sea levels. For example in the Darwin museum is a 6m long dug-out canoe that in 1964 accidently sailed over 300 km from Selaru, in Indonesia, to Australia with 2 women 4 men and 4 children on board.
Such a single fishing family would be quite capable of surviving and multiplying to eventually populate the continent. But they are probably just one of many thousands of such accidental crossings in the last dozen or so millennia.
A 6m long dug-out canoe from Selaru in Indonesia (2 outriggers not attached) - Darwin Museum
The Darwin Museum has a collection of boats intercepted coming to Northern Australia in just 25 years. Boats like the ones pictured are very difficult to detect. How many actually arrived in that time?
Archaeological evidence is mounting for quite frequent commerce and even human migration between northern Australia; Indonesia and New Guinea; most recently Melanesian and European. Ancient ceramic and metal traded objects are found with increasing regularity. Artefacts have even been found that originated in Africa.
Even if the necessary seafaring technology had never been developed or was forgotten in parts of Australia, this was not the case in the Torres Straight or Cape York, where inter-island navigation extended for hundreds, sometimes thousands, of miles.
And as a plaque in Darwin records, in 1952 the artist Ian Fairweather demonstrated that even the simplest of rafts is adequate to travel between Australia and Indonesia.
The Darwin Museum has a collection of 13 boats intercepted coming to Australia