When I dropped down and entered the chamber for the first time, it was awesome in the true sense of the word. Everywhere my headlamp shone, I saw fragments of bone. We expected to find a single individual, probably a species we already knew. But there were 18 hominins, each around 300,000 years old. We later learned those remains came from a previously unknown human cousin, Homo naledi. We believe this species deliberately disposed of their dead there.