I'm curious about this statement: "They would have needed control of a light source like fire." Why is that? By that I mean, why would it have been impossible for H. naledi to have navigated to the excavation chamber (or at least to the top of the chute leading to it) without an artificial light source? Granted it seems unlikely, but is it more unlikely than a much earlier use of fire than previously believed? Has that question been discussed much so far? Thanks!

They would have needed control of a light source because thechamber and the route to it is pitch dark. Without a light, there is no way tonavigate in that environment, let alone to the extent that H. naledi must have done to reach the chamber that they did. Onceyou move past the entrance of the system about 5m, there is no light and theterrain is treacherous. Remember, it looks as though the path into the chamberhas changed very little geologically/topographically over the interveningperiod of time (no skylights). I think the idea that they would have navigated the path intothe system without a light sourcelike fire much more difficult to believe than the scenario in which they wereusing it. Plus, we have no dates for H.naledi yet. We don’t know how early or late they are! There is evidence tosuggest that the lineage might be fairly old but this isn’t to say that thefossil are as old as the lineage. They could be younger or they could be as oldas their brain size and parts of their postcranial anatomy suggest. If H. naledi does obliquely provideevidence for an early use of fire, then that’s pretty cool I think! I mean, theevidence already suggests that they were participating in some pretty complexbehaviours. What’s fire use after that?