I admit I don't really know. The story I read suggested that settlers sailed from Africa directly. But I don't know what the actual scientific consensus is on this. Really I don't find it particularly interesting as it's mostly guesswork about something 65000 years ago
Genome sequencing of ancient human bones has revealed a ton of interesting evidence about ancient human migration patterns! See the book Who We Are and How We Got Here
On a related note, something that has always intrigued me is why there is no historical record of Polynesian arrival on the east coast of Australia.