One of the programs on NatG a few years ago had an episode about the finding of Jomon-type pottery in digs in an area of S America dating back 1000’s of years-the archaeologists were speculating whether the pottery was a part of trade-goods brought from what is now Japan or locally made by settlers from the Jomon area of Japan-either way, it establishes a much earlier date for sea travel from what is now Japan to what is now S America-humans have always been a lot more innovative and clever than they are given credit for-trade was what made people travel and explore from the beginning-and it just makes sense that they used boats-low sea levels so they could shore-hug made sailing the path of least resistance...
Maybe they were talking about this?
https://en.wikipedia.org/wiki/Valdivia_culture#Influences_on_Valdivia_culture
additional sidebar from blam’s link:
http://factsanddetails.com/japan/cat16/sub105/item484.html