The current theory is that civilizations appeared across the planet due to climate change. This theory is based on the hypothesis that humans pre-1500 didn't have any contact with one another.
I've been suspicious of that claim. If the Polynesians came from Asia and were able to reach the Americas, it's possible that there was latent communication between the two worlds but such communication happens at "generational" speeds.
I've been suspicious of that claim. If the Polynesians came from Asia and were able to reach the Americas, it's possible that there was latent communication between the two worlds but such communication happens at "generational" speeds.