Odd stuff I've read. There wasn't no contact. But contact was very limited. It's northern Australia is 100-300 miles from parts of Indonesia, Papua New Guinea, etc.

Also also genes that don't confer any particular advantage tend to peter out when inserted into large populations.

Above my pay grade but I think that argues that the genetic difference that do exist tend to either not confer any particular advantage, like maybe shape of your nose, hair color. Or confer some limited advantage, skin pigmentation for instance seems to be strongly associated with solar radiation and dietary availability of Folic Acid and Vit D.