Indigenous Australians are the Aboriginal and Torres Strait Islander people of Australia, descended from groups that existed in Australia and surrounding islands prior to European colonisation. The earliest definite human remains found in Australia are those of Mungo Man, which have been dated at about 40,000 years old, although the time of arrival of the first Indigenous Australians is a matter of debate among researchers, with estimates dating back as far as 125,000 years.
There is great diversity among different Indigenous communities and societies in Australia, each with its own mixture of cultures, customs and languages. In present-day Australia these groups are further divided into local communities. At the time of initial European settlement, over 250 languages were spoken; it is currently estimated that 120 to 145 of these remain in use, and all but 13 are considered to be endangered. Aboriginal people today mostly speak English, with Aboriginal phrases and words being added to create Australian Aboriginal English (which also has a tangible influence of Indigenous languages in the phonology and grammatical structure). The population of Indigenous Australians at the time of permanent European settlement has been estimated at between 318,000 and 1,000,000 with the distribution being similar to that of the current Australian population, with the majority living in the south-east, centred along the Murray River.