>> Wouldn't that be cool.
Oh yes indeedy! As you say one does not have to exclude the other.
Some recent skeleton discoveries in the US have put some doubt that the south American population came via north America. There have also been some indications that early north American people didn't cross via the north. This could just be an anti-Native American thing though to say that 'hey, you stole it before we did!', so it may be crap. It all gets very interesting ...