Lazarus Kgasi: DITSONG: National Museum of Natural History

South Africa is famous for its richness in hominid discoveries and we find these fossils preserved deep inside caves arising from the fact that bones and teeth are fairly resistant biological material. Certain geological conditions are required for them to be preserved in the process called fossilization. They have to be buried deeply in a sediment(soil) that may become cemented by calcite over time and this calcified material is referred to as breccia.

Before the phenomenon of fossilization occurs, the bones have to be transported into a cave. To do so, there are several potential biological and non-biological factors contributing to these bone accumulations. Carnivores bring their prey into their dens; porcupines carry bones into the caves to gnaw on; owls and eagles roost at the entrance of caves and regurgitate pellets full of hair, feathers, bones and dental remains and animals can also fall into the cave opening and die. Bones left lying at the entrance of a cave, carcasses brought by predators or animals having died a natural death can fall into the cave either by gravity or washed into the cave by flowing water adding to these bone accumulations. Some animals use caves as a shelter to protect themselves from the climate and predators.

 Figure 1.  Map of Bolt’s Farm cave deposits indicating the location of Cobra Cave.

Bolt’s Farm Cave System is one of the fossil bearing sites located in the Cradle of Humankind World Heritage Site. Bolt’s Farm is a complex site composed of over 20 sites, each with a specific name to differentiate them from each other. Today, Bolt’s Farm spreads over three properties, namely: Main Quarry, Klinkert’s property and Greensleeves property. Cobra Cave is one of the sites forming part of the Bolt’s Farm Cave System.

Various people have excavated at Bolt’s Farm since its discovery in the 1930s. Of interest to this paper is the 1947-1948 expedition, known as the California African Expedition. This expedition was led by Charles M. Camp, who mapped and undertook the first systematic sampling of the numerous fossiliferous sites at Bolt’s Farm. Most of the specimens that were collected were exported to the University of California-Berkeley in the United States where they still reside. Cobra Cave was one of the caves that was mapped by this team and it was initially given a derogatory name that does not have a place in the new South Africa, and thus need not be mentioned here. For now, this site will be referred to as site X.

Figure 2. Skull of the extinct African pig Metridiochoerus modestus from Cobra Cave.

In 1996 a collaborative programme between South Africa and France was established. During this time, team members undertook fieldwork at Bolt’s Farm, which resulted in the discovery of a new site, Waypoint 160, which is currently the oldest site so far discovered in the Cradle of Humankind (dated between 4.5 and 4 million years).

From 2006-2010 the survey of Bolt’s Farm Cave System intensified and additional new sites were discovered. Systematic sampling was done on each site and the collection of breccia blocks greatly increased. Lingering in our minds was the existence of site X with the derogatory name and we could not until then come up with a suitable new name. It was in the middle of October and we were excavating outside the cave, as we were sweating from the heat of the sun we decided to go inside the cave to prospect the inner part of the cave. As we were walking in a single file towards deeper parts of the cave, my eyes were drawn towards the wall of the cave and I saw a long greyish thing on the side of the cave entrance. When I pointed my light towards it, it appeared like a snake and I screamed “COBRA”, and ran towards the exit. Two colleagues were in front of me and one of them, had a snake as a pet, so she was naturally curious and pointed her light towards the so-called snake. It was then discovered that it was not a snake, it was a weathered orange sage bag. That is how we decided to name the site Cobra Cave and removed the derogatory name it once carried that was not representative of the team in the new South Africa.

Excavating at Cobra cave will always bring memories of what happened on that day and hopefully we will discover fossilized cobra to complement the name!