Canadian researchers help uncover oldest evidence of human activity in African cave

Archeologists and geologists work inside Wonderwerk Cave to date evidence of human activity. (Credit: Michael Chazan)

TORONTO — A team of archeologists and geologists has confirmed the oldest cave dwelling at Wonderwerk Cave in South Africa's Kalahari Desert, dating back nearly two million years.

Wonderwerk Cave is an archeological record that spans over millions of years and holds evidence of some of the first use of fire and tool making by prehistoric humans.

The study, led by the Hebrew University of Jerusalem and the University of Toronto, published in Quaternary Science Reviews, has confirmed the date of this site.

"We can now say with confidence that our human ancestors were making simple Oldowan stone tools inside the Wonderwerk Cave 1.8 million years ago. Wonderwerk is unique among ancient Oldowan sites, a tool-type first found 2.6 million years ago in East Africa, precisely because it is a cave and not an open-air occurrence," lead author, Ron Shaar at Hebrew University's Institute of Earth Sciences, said in a press release.

The team of researchers was able to determine that the shift from the Oldowan tools, sharp flakes and chopping tools, to early hand axes occurred more than one million years ago.

Deep inside the cave they also found evidence of early uses of fire from one million years ago. There were burnt bones, sediment, tools and even ash. According to the press release, the discovery of fire use inside the cave is significant because most evidence of early human fire use occurred in outdoor spaces where wildfire can’t be excluded as a possibility.

Due to the difficulty of dating cave deposits, the team worked on a 2.5-metre layer of sedimentary material using paleomagnetism and burial dating.

"We carefully removed hundreds of tiny sediment samples from the cave walls and measured their magnetic signal," Shaar said in the release.

According to the press release, magnetization would have happened when clay particles from outside the cave went inside and landed on the cave’s floor. These particles would preserve the direction of the Earth’s magnetic field at the time they entered the prehistoric cave.

"Our lab analysis showed that some of the samples were magnetized to the south instead of the north, which is the direction of today's magnetic field,” Shaar said. “Since the exact timing of these magnetic "reversals" is globally recognized, it gave us clues to the antiquity of the entire sequence of layers in the cave.”

A second method was used to further confirm dating of the human activity in the cave.

“Quartz particles in sand have a built-in geological clock that starts ticking when they enter a cave. In our lab, we are able to measure the concentrations of specific isotopes in those particles and deduce how much time had passed since those grains of sand entered the cave," Ari Matmon, Director of HU's the Institute of Earth Sciences, said in the press release.

Co-directors of the Wonderwerk Cave project, University of Toronto’s Michael Chazan and Hebrew University’s Liora Kolska Horwitz, said that these findings play an important role in understanding the rate of evolution in Africa.

“With a timescale firmly established for Wonderwerk Cave, we can continue studying the connection between human evolution and climate change, and the evolution of our early human ancestors' way of life."