At the start of the game, the Barbarians are really the only enemy (unless one immediately starts to seek out other civilizations). It is possible to go several turns without having any encounter with any other civilization, but it is nearly impossible not to come across these foes. They always have a few villages scattered across the land. The Barbarian villages are usually near the main player-controlled civilization, so finding them shouldn't take much more than a few turns (by which time one may be able to combine three Warrior units to create an army).