Wit respect to the second point of your post, I find the conclusion highly speculative and suspect - just another attempt to prove that humans are "special' and somehow very different from the rest of the animal kingdom. It is very simple - Neanderthals didn't cross large bodies of water because they didn't have watercraft. Would neaderthals or homo erecti have ventured out to sea if they had watercraft? Who knows? One thing, when you venture out onto the water, accidents happen. Storms arise and you get blown off course. Currents set you into unknown locales. Sometimes this results in accidental discoveries.

Now we have the technology to contemplate voyages to Mars. We will try it. But without the technology, we would just be pounding sand, or maybe stll fashioning flint knives.