forum.freeciv.org

In freeciv 3.x should been introduced barbarian animals. In my opinion, units of this kind should give an option called "create resource". In first step this kind of unit should lose battle and special units should enslave it.

Imagine we enslaves elephant and after discovering animal husbandry, we would build camp by create resource option, which gives us possibility to byuld War Elephants unit.

"Animal" type barbarians are already implemented in 2.6, though the supplied rulesets don't use them. They are created upon world generation and don't naturally move from their spots. By making them capturable, maybe only to certain "tamer" units (which is possible in 3.x), they could be tamed for your civ. However, I don't think there's currently a way to make that a requirement for producing more units.