Europeans were not the first non-Australians to come into contact with Australian Aborigines after the continent was first reached by modern humans ca. 50,000 years ago. We know this because the dingo (a type of dog related to Southeast Asian dogs) appeared there ca. 4,000 years ago and led to a secondary mass extinction event in Australia. Most likely, the dingo arrived via trade with Austronesian mariners. There is also some evidence of South Asian autosomal DNA in some aboriginal Australians, which could date to contact in this time period.
But, a link between aboriginal Australians who have Y-DNA C and South Asians with Y-DNA C, originally estimated to suggest a recent common ancestor ca. 5,000 years ago around the same time as the arrival of the Dingo has upon re-examination been determined to be a false alarm. In fact, the most recent common ancestors of aboriginal Australian Y-DNA C and South Asian Y-DNA C is actually closer to 50,000 years ago, in accordance with a no recent contact hypothesis.