On September 10th, 2015 we learned about

Cramped cavern yields colossal clutch of hominid fossils

The human family tree was recently confirmed to have a new branch. Or perhaps an addition to the trunk? It’s hard to say, as Homo naledi seems to have features that would be at home on a human, but others that are a better match for a more primitive relation. Their brain was around the size of an orange, but their feet were stiffer and more suitable for walking like ours. Their jaws were small, like an Australopithecus, but their molars were a better match for Homo sapiens. While there are still a number of questions to be answered, we have an amazing amount of data to work with thanks to the somewhat amazing story of how H. naledi was discovered.

Loosely buried but well hidden

Anthropologist Lee Berger was exploring caves in South Africa, explicitly for the sake of exploring new territory. There was reason to suspect the Rising Star cave might be interesting, but what transpired was nearly worthy of Indiana Jones, or maybe the Goonies if you removed the booby traps. An accidentally discovered crevice led to a nearly 40-foot shaft so narrow Berger himself couldn’t fit through it. A caver assisting the exploration managed to get through it, and immediately found bone fragments sitting out in the open. A proper investigation was needed, but it required the assembly of a special team first.

The team Berger put together didn’t need a demolition specialist, but they were otherwise a very elite group. They needed some field experience with paleontology or archaeology, they needed to have caving experience, they couldn’t be claustrophobic, and they needed to be small enough to fit through the narrow shaft without too much difficulty. Oh, and they needed to be ready to go within the month. The all female-team was brought together with amazing ease, and then went on to be the front line of the excavation, working in six-hour shifts, often on their hands and knees in the dark cave. They were supported by a 60-member team at camp, communicating via fiber optic cable while they carefully dug out what was a treasure trove of fossils.

Enough fossils to span generations

While many ancient animals are identified only from single bones, H. naledi was represented by over 1,500 pieces of bone from 15 individuals. The group of skeletons were young and old, male and female, and showed no signs of serious injury. The range and scope of the fossils allow for an unprecedented amount of detail in the analysis of the new species. It also raises the question as to why such a robust collection of bodies was in this cave in the first place.

The site was obviously fairly inaccessible, and there were no signs that it had been a lair for a large predator of some sort, leaving its left-overs for our eventual discovery. The bodies weren’t obviously injured, and there wasn’t evidence of cave-ins or flooding depositing them in that location. It was also a very clean site, without the usual scraps and debris left by hominid occupants, indicating that they hadn’t really been living there (and with adult H. naledi being around five-feet tall, they probably could have made it through the narrow caves.)

Family burial plot?

While scientists try to to ascribe motivation to their finds, it’s hard to ignore remaining possibilities that point to deliberate placement. Did these relatively small-brained creatures treat this as a burial site? Were the bodies placed there for a purpose? If so, it might demand we rethink the timeline of human development, since ritual burial wasn’t thought to have been invented until the Paleolithic Neanderthals or possibly Homo heidelbergensis. This should be clearer once the fossils from Rising Star Cave are finally dated. At this point, they’ve strangely been unable to ascribe a date to the bones, but it’s hoped that Berger’s team will be able to fill in this critical information as they continue to excavate the cave.

Source: 6 Tiny Cavers, 15 Odd Skeletons, and 1 Amazing New Species of Ancient Human by Ed Yong, The Atlantic

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