And they did all of this while breathing technical diving mixtures and managing the complex logistics of deep cave diving.

The work proceeded over multiple seasons beginning in 2009, two years after the initial discovery.

Season after season, the team documented more of the chamber, recovered more data, and built up the picture of what Hoyo Negro had contained and what it could tell them.

The animal bones on the chamber floor dated to the same broad period as the human remains — the late Pleistocene and early Holocene, the period at the end of the last Ice Age.

Gomphotheres, ground sloths, the various megafauna that populated the Americas before their extinctions.