Convoluted human evolution: H naledi burials, art? , fire? (Introduction)

by David Turell , Tuesday, June 06, 2023, 22:09 (325 days ago) @ David Turell

A brain size only one third or so of ours and doing these things?:

https://www.scientificamerican.com/article/this-small-brained-human-species-may-have-bu...

"Researchers working in the Rising Star cave system near Johannesburg, South Africa, report that they have found evidence that the small-brained fossil human species Homo naledi engaged in several sophisticated behaviors that were previously associated exclusively with large-brained hominins. Describing their findings in three preprint papers that were posted on the server bioRxiv on June 5 and will be published in the journal eLife, they contend that H. naledi, whose brain was around a third of the size of our own, used fire as a light source, went to great lengths to bury its dead and engraved designs that were probably symbolic in the rock walls of the cave system. The findings are preliminary, but if future research bears them out, scientists may need to rethink how we became human.

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"The fossils revealed a hominin with an unexpected combination of old and new traits. It walked fully upright like modern humans do, and its hands were dexterous like ours. But its shoulders were built for climbing, and its teeth were shaped like those of earlier hominins in the genus Australopithecus, explains team member John Hawks of the University of Wisconsin–Madison. Most striking of all, H. naledi had a brain size of just 450 to 600 cubic centimeters. For comparison, H. sapiens brain size averages around 1,400 cubic centimeters. Berger and his team announced the discovery as a species new to science in 2015. Two years later they were able to establish the age of the fossils, dating them to between 335,000 and 236,000 years ago—surprisingly recent for a species with such a small brain and other primitive traits.

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Berger and his collaborators argued, was that H. naledi individuals entered this subterranean cave system deliberately to deposit their dead. If that were the case, they must have used a light source—namely fire—to navigate Rising Star’s dark and treacherous tunnels, chutes and chambers. But mortuary behavior and control of fire have long been considered the exclusive purview of larger-brained hominins. Without any direct evidence of fire or deliberate interment of the bodies, the suggestion that H. naledi might have been surprisingly sophisticated, given its small brain size remained firmly in the realm of speculation.

"Subsequent work in the cave has materially strengthened that case. Berger and his colleagues report evidence for burials in two locations in Rising Star, the Dinaledi Chamber and the Hill Antechamber. H. naledi corpses were intentionally placed in pits that had been dug in the ground, and the bodies were then covered with dirt.

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"Berger finally ventured into the heart of Rising Star. And that’s when he noticed soot on the ceiling and charcoal and bits of burned bone on the floor, which indicated that fire had been used in the cave. At the same time, team member Keneiloe Molopyane of the University of the Witwatersrand, who was excavating another part of the cave system known as the Dragon’s Back, found a hearth. “Almost every space within these burial chambers, adjacent chambers and even the hallways ... has evidence of fire,” Berger says.

"Berger also made another, arguably more astonishing discovery that day in Rising Star: designs carved in the cave walls. The engravings consist of isolated lines and geometric motifs, including crosses, squares, triangles, X’s, hash marks and scalariform, or ladderlike, shapes. The markings were deeply incised into dolomite rock in locations close to the burials in the Dinaledi Chamber and Hill Antechamber. Dolomite is a particularly hard rock that measures around 4.7 on the Mohs scale of mineral hardness—“about halfway to a diamond,” Berger says. That means the engravers would have had to put considerable effort into making these marks. The engraved surfaces also appear to have been smoothed with hammerstones and polished with dirt or sand, according to the researchers. And some engraved areas gleam with a residue that may be the result of the rock being repeatedly touched.

"If H. naledi, with its small brain, was burying its dead, using fire as a light source and creating engravings, then scientists may need to rethink the connection between brain size and behavior. We need to step back and try to understand “the social and community emotional dynamics that allow this kind of complex behavior without having this big, complex brain,” says team member Agustín Fuentes of Princeton University. Taking this perspective makes us think about human evolution in a new way, he adds, and reminds us that “we know a lot less than we thought we did.” (my bold)

Comment: the findings are so surprising there is much criticism I have not presented since time and research will sort it all out. My bold is a key issue. How many neurons re needed to act like a human? Think of what bird brains can do.