The news is that homo naledi did these things at the same time as humans despite a much smaller brain size, contradicting the social brain hypothesis somewhat. Their cranial capacity was 465-610 cubic cm compared to about 1,300 for humans [1].
If humans were around at the same time as homo naledi, how do they know that it was homo naledi? Couldn't a random human just wander in one afternoon and make the marks?
They can't know that for certain! See Lee Berger's announcement video [1] for a discussion. Paraphrasing the slide:
There is no evidence of *homo sapiens* use or presence beyond the light zone of the cavern system
Cultural context: there are *homo nadeli* graves in the cave system with the drawings
Access to the cavern system has not changed and would have been much easier for the smaller *homo nadeli* (Lee Berger had to lose 55 pounds to fit into the caves)
The burials and drawings were made over a long period of time, implying an ongoing settlement
The evidence for *homo nadeli* burials meets or exceeds that accepted for ancient *homo sapiens* burials
That last bit is the most interesting one. Since there are almost no fluvial or geological changes in the cavern system over hundreds of thousands of years, the graves of the homo nadeli are much better preserved than ancient homo sapien graves. By comparing the layers of dirt in the grave and the rest of the cave system, they can determine to a high degree of certainty that it was in fact a purposeful burial instead of a random "body in a hole".
I still don't understand how burials indicate how it was Homo Nadeli who made the marks. All it would take is a single human (maybe some teenagers) wandering down one afternoon on a lark and making the marks.
Having read his "Almost Human" book... these are not caves you casually enter. The passages to get to the Naledi burial chambers are impassable to adult males and most women, and are very deep and far in the cave system. He specifically recruited petite women with caving experience to work on his projects.
"A portion of the cave, used by the excavation team en route to the Dinaledi Chamber, is called "Superman's Crawl" because most people can fit through only by holding one arm tightly against the body and extending the other above the head, in the manner of Superman in flight"
That makes it even more likely it could have been humans, doesn’t it? Over a long period of time, probably lots of humans wandered deeper into the cave.
Now I'm picturing two cave dwelling fellows in front of a fire knapping flint and shooting the shit, and one goes "hold on, what about cave paintings... as a service!"
From just scrubbing through the video it seems like there’s none of the usual evidence they were done by humans in the cave, I guess like random other trinkets or items? The cave is super super small, and if I understood correctly it was also a burial ground for Homo naledi.
They’re not terribly sophisticated markings, or obviously social. Even if brain size correlates exactly with capability, doing these at ~40% brain size seems quite plausible.
Brain size in modern humans is also only weakly correlated with intelligence [1]. So they might not even have been stupid due to their smaller brain size.
Sperm whales don't have much of a chance to manipulate their environment, but they have the largest brains on earth [2].
(dang would have moved your comment as title-change comments get pinned to the bottom of the list when resolved, so this gives your useful comment better visibility)
You took the trouble to italicize the binomial, but didn't capitalize the generic name, whereas the OP's title failed to not capitalize the species epithet.
