Paceman Kagiso Rabada bowled an understrength South Africa to a 177-run victory over Australia on Monday, giving the visitors the upper hand at the start of the three-test series.
The South Africans entered the series without injured captain A.B. de Villiers, and their depth was tested when pace spearhead Dale Steyn fractured his right shoulder on the second day and was ruled out of the remainder of the series.
The young attack, led by man-of-the-match Rabada's 5-92 in the second innings, rallied to ensure South Africa continued its unbeaten run in tests at the WACA ground and ended a long streak for the Australians, who hadn't lost the first test of a home series since 1988.
Australia started on top, having the South Africans reeling at 81-5 on the first day before bowling them out for 242. After a commanding start to the reply, with opening pair David Warner and Shaun Marsh putting on 158 runs, the Australians lost 10 wickets for 86 runs.
The slide was triggered by Steyn's dismissal of Warner for 97 - the veteran South African bowler's last act of the series.
Skipper Steve Smith was unhappy with how Australia has batted recently, starting with the 3-0 test series loss in Sri lanka in August.
"It's happened a little bit of late and the batters have to work hard to rectify what they are doing out in the middle," Smith said. "We need to form some more partnerships and get big first innings totals.
"South Africa are formidable opponents and they outplayed us in this test match and we are going to have to play a hell of a lot better if we want to compete with them in the next game."
The depleted South Africa lineup dictated play from there, with Dean Elgar (127) and Jean-Paul Duminy (141) sharing a 250-run stand for the third wicket to set up South Africa's 540-8 declared.