Israeli scientists find earliest use of fire in Miracle Cave

Israeli scientists have uncovered secrets of our evolution deep in a cave in the Kalahari Desert.

A group of scholars from the Hebrew University of Jerusalem’s Institute of Earth Sciences and the University of Toronto took an exciting step in understanding more about early human activity dating back millions of years. This was due to extensive work in the Wonderwerk (Miracle) Cave in the Kalahari. This includes the uses of tools and fire.

The cave is situated in an ancient cavity in the dolomite rocks of the Kuruman Hills, between Daniëlskuil and Kuruman in the Northern Cape.

“New research has enabled our team to confirm the age of some critical events in the Wonderwerk Cave,” says Dr Liora Kolska Horwitz, an affiliate researcher with the Hebrew University’s National Natural History Collections.

“Using new methods, we have dated the lowest level of the cave with evidence of occupation by prehistoric humans to 1.8 million years ago. In the layer immediately above this that is now dated to between 1.8 million to just over 1.2 million years ago, there was a shift in tool-making capabilities of the occupants. At about one million years ago, there is robust evidence inside Wonderwerk for the use of fire, and this is the earliest evidence of human use of fire worldwide.”

Kolska Horwitz describes herself as a “South African-Israeli. I was educated at Herzlia Schools and the University of Cape Town, where I studied archaeology. While on a visit to South Africa in the early 2000s, I looked for a suitable project to work on. At the time, there were very few people working in the interior of South Africa and even fewer on the time period that interested us – the earlier Stone Age. The rest of the story is [pre]history!”

“Wonderwerk is probably the first cave on earth to have housed human activity,” Kolska Horwitz says. “All other sites of this time period were open-air occurrences – so early humans ‘camped’ out in the open. Artefacts have been recovered from sites in the Cradle of Humankind, but these are considered to have been washed into the sites. At Wonderwerk, these finds didn’t fall into the cave or were washed in, but are in situ. The new ages for the site conclusively prove it to be the earliest cave occupation in the world at 1.8 million years ago. Notably, the first stone hand axes found in the cave are some of the oldest-known in southern Africa.

“Wonderwerk has provided the most convincing and earliest evidence for the use of fire by early hominins,” she says. “Human use of fire for defence, illumination, warmth, and most importantly cooking, is thought to have been the driving force of key aspects of human evolution. Cooked food reduced the energy used in digestion, and this led to major changes in human digestive anatomy, tooth, jaw size, and facial shape. The reduced energy expended on digestion could then be channelled to brain growth, resulting in increased brain size.

“The cave is also quite unique in preserving a long and almost continuous record of human activity starting nearly two million years ago up until the early 1900s – when the farmer who was occupying the cave moved into his farm house,” she says. The cave is 140m long.

The team has been working at the site for 15 years. “I co-direct the Wonderwerk project with Professor Michael Chazan of the University of Toronto,” says Kolska Horwitz. Chazan told the SA Jewish Report that “as a Jewish Canadian, it has been fascinating to learn a bit about the Jewish community of Kimberley. The warm welcome we have received when able to join the Friday evening minyan has made it easier to be so far from home.”

Professor Ron Shaar of the Hebrew University explains some of their intricate and painstaking work. “We carefully removed hundreds of tiny samples of sediment from the cave walls and measured their magnetic signal. Magnetisation of the sediment occurred when clay grains, that entered the cave from outside, settled on the prehistoric cave floor, thereby preserving the direction of the earth’s magnetic field at that time. Our analysis in the lab ‘unlocked’ this magnetic signal, and showed that some of the samples were magnetised to the south instead of the north, which is the direction of today’s magnetic field. Because the exact timing of these magnetic ‘reversals’ is globally recognised, it provides us with clues as the antiquity of the entire sequence of layers in the cave.”

Professor Ari Matmon, also of the Hebrew University, explains cosmogenic burial dating. “The sand grains outside the cave contain quartz grains that are exposed to cosmic radiation and act as a trap for elements called ‘cosmogenic isotopes’. When the sand grains enter the cave, these elements trapped inside the quartz begin to decay. In the laboratory, we are able to study the remaining concentrations of cosmogenic isotopes and determine when the sand entered the cave and became part of the archaeological layer. This gives us an age for the archaeological layer.”

“We aren’t an official Israeli excavation as we receive no funding from Israeli institutions or the Israeli government,” says Kolska Horwitz. “Our funding is from international funding agencies but mostly from the Canadian government so, if anything, we are considered a Canadian excavation with Israeli team members, but we also have American, Canadian, European, and South African team members.

“In fact, more than half our research team is made up of local scientists from South African institutions. This includes the University of the Witwatersrand, University of the Free State, Sol Plaatje University, Iziko South African Museum, the National Museum of Bloemfontein, and most importantly, the McGregor Museum in Kimberley, which is responsible for the cave.”

She says they aren’t just involved in researching the past, but are also doing public-heritage outreach work with local communities, dedicated to educating and preserving heritage sites in the Northern Cape.

“For example, every year we organise a ‘culture in the cave’ event, including tours of the cave for local communities. Many people living less than 100km away have never visited the site and don’t know much about the important finds. We also arrange theatre performances on evolution and environmental issues at the cave and in local community centres and schools. These are performed by the Walking Tall theatre group from the University of the Witwatersrand. We also run a field school each year for students in Heritage Studies at the Sol Plaatje University in Kimberley.

“It’s been an exceptional experience and privilege for us to work in this wonderful region, and to engage with our local colleagues and communities in Kimberley, Kuruman, and Bloemfontein,” Kolska Horwitz says. “They have shown us warm hospitality and helped us in so many ways. We look forward to continued collaboration.”