More on Irish and Portuguese DNA links here http://www.megalithic.co.uk/article.php?sid=2146412362

Australia was reached by early man long before they reached Europe. With lower sea levels, the routes via Indonesia, Sumatra, Java and Borneo, New Guinea presented no difficulty as many of the island were hills on a low lying plain. Then it was just a short hop over to northern Australia.

Earliest dated human remains in Australia are 50-60,000 years ago when we were all suupposed to be still in Africa. A contoversial theory being argued now is that the first humans evolved in Asia and not Africa. The argument goes that we have only found African remains because of the dry climate and geology of places like the Olduvai Gorge. It is suggested that earlier remains either were never fossiled in Asia or were, but have not yet been found.