I am playing an emperor game, and almost every AI was on my conitnent, with one poor isolated AI. As such sea faring was not important to me so I teched the requisite techs very late (at sci meth time, for other things; oddly, no one else had it, so it was a weak trade bait too). However, after having optics for a while, I realized no one had circumnavigated the world, so I went for it. It was unlikely, I thought, as another AI had caravels, but I whipped 2 caravels on either end of my empire and went for it. Eventually I discover the poor isolated AI, in ~900 AD, and realize I am seeing something I've never seen before: The AI didn't have agriculture in 900AD. There was not a single wheat rice or corn on his island, so he didn't need it for resources, but still... unable to make farms in 900 AD! lol