So, I searched for few subreddits for this topic to avoid repetition and haven't found anything. Question: out of all of these theories involving variety of different hypothetically contacting civilizations, which theories are the most scientifically plausible? Can somebody write a personal rank or 'Top 5, 10, whatever' theories that may most certainly survive after the most possibly accurate analysis of their data? Also, I would really appreciate if any of the theories can get some commentary as well, not only the rigid list.
We can still answer this question, but a quick search revealed several links:
Polynesian contact:
What do we know about the sweet potato and Pre-Colombian contact with the Americas and Polynesia?
What kind of contact did the polynesians have with each other and the rest of the world?
How controversial/accepted is the theory that Polynesians travelled to South America?
Egypt, Rome, China etc:
Is there any evidence of Phoenicians or Romans having visited the Americas?
Ancient Rome and the Americas?
Did China discover America in the 14th Century or earlier?
Is there any evidence for Chinese circumnavigation of the globe in the early 1400's?
Did Zheng He ever reach the Americas?
I should point out though that out of all these 'hypotheses', the only one that actually seems to have any real scientific grounding is Polynesia, which seems to be just shy of having real concrete evidence.