@KittenOFChaos, it's a bts thing i believe, warlords and earlier the ais would come through your borders.
@Kid R, that's right ais will use galleys at some point to settle land and in this case they will go through borders as well. I don't think it'll happen before 1000 bc though, probably later but as soon as i can spare a settler (read have the south blocked off) i should probably settle there. There's a potential 3 food city there too, not so easy to build NE/Globe there due to lack of hammers.