the American accent and the Australian accent

Brian   Sun Jun 22, 2008 3:57 am GMT
This question is about the accents in two of Britain's largest ex-colonies.

Where did these accents originate from? What accents are their primary ancestors? Now it's quite obvious that Australian and American accents sound very different from each other and originate from different British accents at different time periods. I'm wondering how people of both countries ended up speaking in such distinct ways from the British.