This is the real problem---trying to define race. It can't be done so scientifically. It is a socio/political designation. One person made a comment that perhaps native Australians referred to themselves as black before Europeans came on the scene. Highly unlikely----compared to what? Usually native populations will refer to themselves simply as people. Race is a sort of myth that we all agree to honor. Populations in certain geographical locations will begin to share similar genetic traits, especially if they are isolated. But genetic tests show that there is more variation between individuals within a 'race' that there are between the 'races'.
So we can look at where these people immigrated from thousands of years ago. It is unlikely that they came directly from Africa to Australia---and if your definition of black is African---then whatever. Is it skin color? Is it hair texture? Is it certain features? I don't know because it is completely subjective. I am quite fair skinned, and I was talking to a racist in my family (dead now) that was arguing that darker skin made one inferior. He was quite a bit darker than me so I asked him if I was better than he was. He said yes.
Now let me tell you a cool story about the Smithsonian natural History museum, and the Aborginal skull I saw there. We can come to understand how insidious and subtle racism is.
I was talking to a guide in front of a large case of homo erectus and homo sapien skulls. She heard an Australia accent and took my elbow and pulled me over to the Aussies. She pointed out an old skull found in Australia--pre-European. She asked if it was homo erectus or homo sapien. Well it kind of looked like both. The shape looked more like erectus, but not exactly. So she told us about some Australian visitors a few months back that had looked over the skull and commented that they always knew "they" weren't human. Then she explained that this skull was misshapen because the population practiced head binding in infants. This was not the natural shape of the skull. She said that in Australia there is one person in charge of sending out antiquities, and when the Smithsonian requested a skull cast----they chose THIS one. This is how it works. She was quite upset with the Smithsonian for displaying it with no explanation, thereby feeding into racist views.
It was a great skull. Very interesting. It belonged in it's own case with an explanation about binding and so forth. That would have been educational. But as far as I'm concerned, the Smithsonian did not do enough to clarify the issue.
NC