 The indigenous population , estimated to have been between 750 @,@ 000 and 1 @,@ 000 @,@ 000 in 1788 , declined for 150 years following settlement , mainly due to infectious disease . Thousands more died as a result of frontier conflict with settlers . A government policy of " assimilation " beginning with the Aboriginal Protection Act 1869 resulted in the removal of many Aboriginal children from their families and communities — often referred to as the Stolen Generations — a practice which may also have contributed to the decline in the indigenous population . The Federal government gained the power to make laws with respect to Aborigines following the 1967 referendum . Traditional ownership of land — aboriginal title — was not recognised until 1992 , when the High Court case Mabo v Queensland ( No 2 ) overturned the legal doctrine that Australia had been terra nullius ( " land belonging to no one " ) before the European occupation . 
