Dancing around a bonfire to the beat of a goatskin drum, a party of Ethiopian men is singing 50-year-old Tigrayan songs about working in the fields and brothers lost at war. With worries draining faster than crates of local Habesha beer, the mood is jovial; intoxicated by rhythm, beatboxers hiss with an electric charge and a daring one-legged man is using his crutch to pole vault over the pyre.

The cause for celebration is our arrival at Koraro cave in the Gheralta Mountains; faranjis (or foreigners) rarely travel this far. Illuminated by leaping flames, an inscription in the rock face sheds light on the human history of this sandy-floored overhang where our dome tents have been pitched for the...