Scientists return to explore a second fossil chamber
Palaeoanthropologist and science blogger John Hawks of the University of Wisconsin-Madison has just returned to South Africa with NG Explorer-in-Residence Lee Berger of the University of the Witwatersrand and others to continue work on the hominin discoveries of the Rising Star caves. Follow him on Twitter @JohnHawks.
By John Hawks
It has been a long three months since we camped out at the site of the Rising Star caves outside Johannesburg, and the summer growth has erased the signs of our presence. There’s no evidence of the Science Tent, and the paths we wore through the chunks of dolomite are now under grasses and red wildflowers.
Our new goal is to investigate a second hominin locality within the system.
Yesterday we climbed down into the cave once again.
Our small team included Alia Gurtov, Rick Hunter, Pedro Boshoff and team leader Lee Berger. Alia is one of the original six excavators from the fall expedition, and Rick and Pedro helped discover the site. We arrived at the gate in the early morning to do a job – Rick on his motorcycle, Pedro in his car, and the rest of us in Lee’s Jeep. After some hugs and handshakes, we headed up to the cave and geared up.
Most everyone following palaeoanthropology by now knows about the chamber that produced more than 1 200 numbered specimens. That chamber, inaccessible except through a very narrow 12m chute, was the focus of our expedition in November. Since then, a team of scientists from Wits University – including me for the last two weeks – has been working on those bones. Every site represented in the Wits collection has a number; for example, Malapa is site 88. Every specimen plotted by the advance team during our November expedition was tagged in the cave, and given a number beginning with UW-101, for University of the Witwatersrand, site 101.
Every specimen, that is, except for four.
In the final days of the expedition, Rick and Steve Tucker had gone looking through the cave system for more fossils. They found a second area with bones, which we designated site 102. On the last day of our November run, this became the second hominin-bearing locality in the system when Marina Elliott and Becca Peixotto brought out four bone fragments that we could diagnose as hominin.
Return to site 102
Yesterday we went to investigate this bone assemblage. Our main interest was to get some facts that would help us best plan future excavation. We needed to determine the overall condition of bone in the site, and to see if any of the bones were at risk of disturbance or erosion within the cave.
We headed into the cave, descending by a different route than the one leading to site 101. It may seem strange that after so much time underground in this cave, our team still can be surprised at new passages, but going through the inside of this hillside is a little like playing three-dimensional chess. The cave system is a complex series of multi-layered passages between intersecting fault lines in the dolomite. If you think about the structure of the geology, it begins to makes sense.
That may not help too much when you’re crawling through a narrow tunnel as your friends pass 7m overhead.
The five of us clambered down a series of tight drops, then shimmied carefully around a hole 10m deep. I would soon be on the floor at the bottom of that hole, but happily after a controlled descent.
I do not have what you could call a spelunker’s physique. I did discover that the advantage in caving is not always to the small, as some of the drops benefited from long legs to reach downward. But halfway down our route was a squeeze – a narrow passage between two vertical walls, only around 22cm wide, the floor sloping downward. For Rick and Alia, that was no problem at all. Either of them could have worn a backpack through it. Lee squeaked it. Pedro and I share the curse of a barrel chest. No chance of getting through.
And so, we headed off toward other parts of the cave to inspect some fossil-bearing breccias (natural concrete-like rock) for signs of australopithecines. Rick, Alia and Lee went on down, another 20m or more vertical distance, to site 102.
Between rocks and a hard place
When they got there, they found the bone assemblage and assessed its condition. They recovered a few additional pieces from the surface of the deposit, recording them and doing field identification of the bone fragments. It was meticulous work, and they took around two hours altogether. Pedro and I found lots of interesting breccia, with carnivores and bovids, but nary a hominin.
I cannot report that the trip was uneventful. As Rick, Alia, and Lee climbed up from site 102, they encountered that squeeze again. Rick and Alia once again breezed through. Not so for Lee – he stuck. I mean really stuck. What had been a relatively straightforward path going down became a very difficult path coming back up, chest wedged between the vertical walls. For 45 minutes he exerted against the rock.
I propped myself into a vertical shaft, 2m up, and looked down six slices in the dolomite, radiating outward from me like the arms of a snowflake. White sheets of calcite rippled in one of the arms, thin crystals grew in another. Alia sat above me and we waited as Pedro and Rick helped Lee free himself. Ultimately, the breadth of a button made the difference, as he removed his coverall and went through T-shirt only. He emerged tired but exhilarated, having explored where only a handful had ever tread before.
After a rest, we climbed our way back up into the sunlight. The underground world had held us for four hours. It seemed more like one.
More to come
There are obviously many unanswered questions about site 102. We do not know how it relates to site 101, if at all. They are far apart within the cave system and we do not know any geological reason why the fossils would necessarily represent the same kind of hominin. Until we can examine the specimens more closely, we won’t know what they are.
Still, we learned a lot about site 102, getting a clear idea of the logistics of excavation there in the future. As the expedition ended in November, we left site 101 knowing that there remain thousands of specimens still in the floor of that chamber. Now we know that the system has at least one other excavation area, and the potential for even more.
Meanwhile, we are planning the analysis of fossils from site 101 this May, with the Rising Star Workshop. Read an earlier post to get the basics, but there will be much more on that to come ...