Sahul is the name given to the single Pleistocene-era continent which combined Australia with New Guinea and Tasmania. At the time, the sea level was as much as 150 meters lower than it is today; and it was separated from the other great land mass (Sunda) by the Sahul Strait. The island in the photograph would have been part of Sahul.
Archaeologists care about this ancient continental shift because to get the Sahul populated, people had to actively work at getting there from the Sunda (in other words, they had to have boats or rafts and were likely to intend getting there). Currently, there are two theories about when this happened: 60,000 or 40,000 years ago. Scholars do agree that there are sites in Australia that date to at least 40,000 years ago, including Devil's Lair, Lake Mungo, Nauwalabila, and Malakunanja. The O'Connell and Allen paper listed below is an excellent review of the recent considerations.
O'Connell, James F. and Jim Allen 2004 Dating the colonization of Sahul (Pleistocene Australia--New Guinea): A review of recent research. Journal of Archaeological Science 31:835-853.