Wits reopens Sterkfontein Caves — ‘a time capsule of identity’ — after 2022 flooding damage

The Wits Sterkfontein Caves is a dolomite cave system that formed about 20 to 30 million years ago. (Photo: Julia Evans)

By Julia Evans

15 Apr 2025

After more than two years of closure due to flooding and infrastructure damage, the Sterkfontein Caves - one of the world’s most significant archaeological sites - reopened to the public.

The Sterkfontein Caves, renowned for their pivotal contributions to the understanding of human evolution, officially reopened on Tuesday, 15 April, after being closed for more than two years following infrastructure damage caused by heavy flooding at the end of 2022. Tickets are now available for the public from Wednesday, April 16

The site, located within South Africa’s Cradle of Humankind, a Unesco World Heritage Site near Johannesburg, is famous for yielding some of the most important hominin fossils, including the iconic “Mrs Ples” (1947) and “Little Foot” (1994-1998), in addition to the hundreds of other fossils of human relatives.

“These discoveries are not just bones in stone; they are a time capsule of identity, windows into our collective past, and mirrors that reflect our complex journey of life here on planet Earth,” said Professor Zeblon Vilakazi, the Vice-Chancellor and Principal of Wits University, at the reopening event.

From left: Wits University’s Vice-Chancellor and Principal Professor Zeblon Vilakazi, Dean of Science Professor Nithaya Chetty, Gauteng Premier Panyaza Lesufi and Mogale City Mayor Lucky Sele at the entrance of the reopened Sterkfontein Caves. (Photo: Wits University)

Cause of closure

Heavy rainfall over just a few days in December 2022 saturated the soil layers, making them heavier and prone to movement. This led to pockets of soil flushing into the cave system, destabilising its structure and raising safety concerns. The site was then closed in early 2023, marking the first time the site had ever been closed to the public.

Professor Nithaya Chetty, Dean of the Faculty of Science at Wits University, explained that the flooding prompted a thorough safety assessment by the university in collaboration with an engineering firm. As part of the rehabilitation process, structural reinforcements were installed, and seismic monitoring equipment was embedded to track rock movement and ensure long-term stability.

Although the flooding was deemed an isolated event rather than a recurring issue, it served as a turning point for the site. The caves have now been formally integrated into Wits University’s academic structure as a dedicated unit within the Faculty of Science, with direct oversight by the Dean. This integration strengthens their role as both a research facility and an educational resource for undergraduate and postgraduate students.

To mitigate future flooding risks, Chetty said the university is enhancing water flow management around the cave system and collaborating with local authorities to address challenges related to the Bloubankspruit.

Dr Stephanie Baker, paleo-anthropologist and principal investigator at the Drimolen hominin site - another important fossil site in the Cradle - explained the caves are formed within dolomite rock, a material prone to erosion when exposed to water.

“Any time it’s exposed to water, it leaches and creates these open avenues that the caves themselves have been formed in,” said Baker. Prolonged water exposure destabilised the site, creating cracks and eroding the softer rock that makes up the cave system.

The Sterkfontein Caves reopened with a media tour at the Cradle of Humankind, Gauteng, on 15 April 2025. (Photo: Julia Evans)

Climate change risks

While attributing the 2022 flooding directly to the climate crisis remains challenging, experts are increasingly concerned about how shifting weather patterns may intensify such extreme events.

Dr Matthew Caruana, archaeologist and co-permit holder at Sterkfontein, noted significant changes in rainfall patterns over recent years, noting that when he arrived in South Africa, at the Cradle, 2009, rainfall was predictable and structured.

“Now we’re seeing crazy patterns with massive volumes of water affecting infrastructure across the Cradle,” he said. He noted that Swartkrans bridge, the only access point to the Swartkrans fossil site in the Cradle, was washed away due to heavy rains as an example of how increased rainfall, an impact of climate change, can impact fossil sites.

Dr Baker also noted that her site (the Drimolen hominin site) has some open-air fossils, and solar erosion - exacerbated by extreme temperature - causing fossils left on the surface to dissolve away if not excavated in time.

The Cradle of Humankind also faces broader risks from climate change-induced hydrological shifts. Sinkholes are appearing more frequently across the region due to changes in drainage patterns and increased surface runoff caused by heavy rainfall events.

The Sterkfontein Caves' fossil technicians. (Photo: Brett Eloff)

Itumeleng Molefe, fossil technician, working in a live excavation site inside the Sterkfontein Caves, Cradle of Humankind, Gauteng. (Photo: Julia Evans)

Fossils frozen in time

The Sterkfontein Caves have provided crucial evidence of our early human ancestors, making it one of the most significant archaeological sites in the world. Among the most remarkable discoveries is “Little Foot”, a nearly complete Australopithecus skeleton discovered in 1994. Dating back over 3.67 million years, Little Foot is considered the most complete early hominin fossil ever found.

The preservation of fossils at Sterkfontein is unique, as the dolomitic caves have provided an exceptional environment for fossilisation. Unlike other sites where bones decay or disintegrate, the unique conditions of the Sterkfontein Caves have allowed many fossil remains to be preserved in almost perfect condition. This has enabled researchers to gain invaluable insights into the anatomy, locomotion and behaviour of early human ancestors.

Job Kibii, the new head of the Wits Sterkfontein Caves, explained: “In some places, animals might die on the surface and their remains decompose. But here, the preservation is almost perfect.” The presence of numerous openings in the cave system allows fossils to fall in and accumulate, creating a record of human and animal life spanning millions of years.

Inside the Wits Sterkfontein Caves Museum. (Photo: Brett Eloff)

A new visitor experience

The reopening of the Sterkfontein Caves also marks a new chapter in how the site engages with the public. While it has long attracted thousands of local and international visitors, the reimagined experience promises to offer deeper engagement with the science that defines the caves.

“This reopening represents a significant evolution in how we share the story of human origins,” said Professor Chetty. “Visitors now have the chance to engage with live science and research happening in real time.”

The new visitor experience will allow people to directly interact with scientists and students conducting ongoing research at the site. Behind-the-scenes tours will offer access to fossil preparation laboratories, where visitors can see the meticulous work that goes into preserving and studying the fossils. Enhanced educational programmes will cover human evolution, paleoanthropology, and related disciplines such as climate science and geosciences.

“There is a fine balance between making this site accessible to the public while protecting its invaluable resources,” Chetty continued. “By opening the doors to the research happening here, we hope to inspire the next generation of scientists and foster a deeper connection to our shared history.”

The Sterkfontein Caves are a dolomite cave system that formed about 20 to 30 million years ago. (Photo: Julia Evans)

The underlying threat of pollution

While flooding and structural issues led to the closure of the Sterkfontein Caves in 2022, the stink of pollution at the Cradle of Humankind is a threat and ongoing concern for researchers.

Dysfunctional wastewater treatment plants - such as the nearby Percy Stewart Waste Water Treatment Works - have allowed untreated sewage to flow into rivers like the Blougat Spruit and Bloubankspruit, damaging ecosystems and posing risks to communities and tourism in the Cradle of Humankind. In addition, acid mine drainage from abandoned gold mines introduces toxic metals into groundwater systems, compounding the threat.

Professor Dominic Stratford, research permit holder at the Wits Sterkfontein Caves, explained that Karst environments, like the Sterkfontein Caves, are vulnerable to water pollution.

“We’ve got lots and lots of caves in the Cradle, and those caves join large underground water networks. So, when there’s acid mine drainage issues from mining in one area, it’s pretty easy for that to start contaminating kilometres and kilometres of groundwater.”

Stratford said Sterkfontein is particularly interesting because of an underground lake inside the caves, which provides a rare opportunity to monitor changes in water quality.

While there’s currently no evidence that the Sterkfontein cave system has been contaminated, Stratford warned that other parts of the Cradle have already been affected. He pointed to the Bloubankspruit at the bottom of the valley, which is quite heavily contaminated from sewage and acid mine drainage, and said that boreholes on private properties in the area have also shown signs of acid mine drainage.

“We monitor [the Sterkfontein Caves] quite regularly, and they have not been affected at the moment,” he said. “But we’re about to launch quite a big study that not only monitors the lake, but also the many other caves on the same property where we have a water table. The idea is to basically have a buffer that we’re using to monitor.

“Because if it gets to the main lake, then you’ve got a big problem - because you can’t stop it.”

Stratford explained that if the caves were ever polluted by acid mine drainage or sewage, it could have devastating consequences: “The acid would start to eat away the cave faster. And then it would change the ecology - so different animals would start using it, or some wouldn’t be able to use it at all.”

Unique species such as blind shrimp, bats and porcupines that inhabit the cave would be particularly vulnerable. Boreholes in the Cradle have already shown signs of acid mine drainage contamination, though some geological features - like dykes that fragment the aquifer - have so far helped isolate Sterkfontein from direct exposure. Still, Stratford cautioned, “It doesn’t mean it will never be.”

At the reopening event, Mogale City Mayor Lucky Sele acknowledged the environmental threats facing the site: “The pollutants from abandoned mines threaten to compromise the very foundation upon which the Cradle of Humankind stands.”

Sele called for urgent investment in key infrastructure, particularly the Percy Stewart Wastewater Treatment Works. “It stands as a bulwark against pollution, and its functionality is crucial in ensuring our waters are clean and safe for both the environment and our communities,” he said.

Gauteng Premier Panyaza Lesufi echoed this sentiment, saying the provincial government is committed to protecting the site. “We are imposing ourselves to be a permanent player in this site,” said Lesufi. “We’ve told the municipality they can count on us for everything they need so that we preserve this area.” DM

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Our Burning Planet

Cause of closure

Climate change risks

Fossils frozen in time

A new visitor experience

The underlying threat of pollution