traffic on Beringia land bridge flowed both ways

Proposing that the original colonists of the Americas were of greater genetic diversity than originally proposed makes sense to me, but there doesn't seem to be any mention of a southern route.

The Beringia land bridge just isn't enough for me anymore. Not only am i sympathetic to the coastal sea route in the Americas, but i'm believing that people crossed the open oceans from Polynesia relatively early. Craziness, but so what?