The first settlement of Australia most likely occurred during the last glacial maximum. During this time Australia and New Guinea were joined as a single land mass called Sahul. The south-east Asian continent and islands were also joined as a single land mass called Sunda. It is theorised that the first Australians crossed the sea between Sahul and Sunda about 60,000 to 40,000 years ago. Other dates have been suggested, and this timeframe is not seen as conclusive. Sunda and Sahul had a permanent water-crossing, meaning that the first Australian Aboriginal and Torres Strait Islander people had to make a crossing on the open sea (see Wallace Line).