The Polynesians did it in the Pacific. Just because we don't know how they would have done it doesn't mean that they couldn't have figured it out (it also doesn't mean that anybody did figure it out).
It is only very recently that the navigational technology of the Vikings has been re-discovered.
I think this is wonderful. Though I am NOT a student of languages, I have been fascinated by the similarities of some words within several languages...Malagasy and Tagalog are two that fascinated me in particular.
After some years of not paying much attention, some smart person (not me) wrote a paper discussing exactly that similarity and supported his or her contention with long-sea routes of exploration from Indonesia going in both directions, i.e. toward the Philippine Islands and toward Madagascar. Of course that person included “word drift”. And that explained to me why I found comfort in Malagasy while living there. It is wonderful how interconnected we are with our current and past.