I think it's becoming more apparent that the ancient civilizations may have had power over nature and used the world's creatures (beasts, sea kings, etc) to wage war against each other. Between roger and Luffy both learning about the world's history and hearing the voice of all things, Shirahoshi being one of the ancient weapons and controlling sea kings, and zoushina being around during the void century and being condemned to wander and compelled to obey commands, a pattern is starting to emerge.
It's like the Manga version of Skies of Arcadia's Gigas, almost.