Lo desconocido: La cueva de los huesos

I enjoyed the documentary and particularly appreciated the cartoon scenes that help the viewer understand the cave system and what this species might have been like. There is one aspect that I just find implausible about the theory of how the bones got to their resting spot. These ape/human creatures somehow ventured deep into a cave system with very tight and steep passageways with no light. It would have been pitch black for hundreds of yards AF advanced cave exploration while carrying their dead. They show an example of how you could bring fire into the cave to light the way. Sure that works for an open area, but the 36 ft chute that is super tight and straight down isn't something you could traverse while carrying lit torches. Plus you'd have to go hours in and hours out which would have required lots of wood. They would have been regularly stuck in the cave with no way to see a thing and died in there. Show me one crew going all the way to the end and back using fire as light and I'm on board otherwise this just isn't believable.