Human habitation of the Australian continent is estimated to have begun 50,000 to 65,000 years ago,^{[24][25][26][27]} with the migration of people by land bridges and short sea crossings from what is now Southeast Asia.^[24] It is uncertain how many waves of immigration may have contributed to these ancestors of modern Aboriginal Australians.^[28][29] The Madjedbebe rock shelter in Arnhem Land is possibly the oldest site showing the presence of humans in Australia.^[25][26][30] The oldest human remains found are the Lake Mungo remains, which have been dated to approximately 42,000 years ago.^[31]