They had found the cave while foraging. It was tucked in the crags of a high cliff wall, accessible only by climbing.
That was 1,115-years ago, and they made it their home. They decorated it with charcoal drawings and colored them using the natural flora found in the lower basin.
Over time, the tribe grew, eventually melding with other nearby tribes until nothing but the crude drawings on the cave walls, a burn pit, and few pottery shards were left. Even the dust forgot that people had once lived there.
Then in the year 3136, archaeologists stumbled onto the antediluvian dwelling.