The first ranged unit in the game can now be built from the very start! However, it is not very effective - it can only attack adjacent tiles, and it's very weak on defense. The best way to use them is from defensible positions (Hills, Encampments, City Centers, etc.), because if any melee unit is allowed to attack the Slinger, he doesn't stand a chance. And he can't stay behind your front line, because he doesn't have the range to shoot over them! Fortunately, they can be cheaply upgraded to Archers once Archery is researched.
Civilopedia entry Edit
Like most early weapon systems, the sling evolved from a tool for hunting game to one for killing people. Simply a pouch between two lengths of cord, the sling was used to swing a projectile – a stone, lump of lead, or anything else convenient – in an arc until such time as it was launched. Although a thrown stone doesn’t have the lethality of an arrow or bullet, it can still do a lot of damage. If nothing else, a rain of well-aimed stones gives an enemy pause before rushing in. And, until composite bows were invented, it had a considerable range advantage over bows and spears. In addition, wasn’t hard to find ammunition. With the exception of Australia, ancient slings have been found in archaeological digs all over the world. Even a barbarian can sling a rock. And, as the First Book of Samuel points out, a slinger can bring down even a Goliath …