Fossils from a coastal cave are proof of how climate change affected our ancestors on the southern Cape shoreline.
Imagine a huge open-plan living area with an uninterrupted view of the sea in Robberg South - that's Nelson Bay Cave, a prime property on the Cape South Coast, 100000 years ago.
The main development has moved to Plettenberg Bay since then, to the north of the Robberg Peninsula. But this beautiful finger of rocky land remains an awesome place to visit. Robberg Nature Reserve offers breathtaking views of the Indian Ocean breaking against rugged cliffs, a breeding colony of seals, a circular trail through fabulous fynbos, a boardwalk route through the breeding ground of thousands of seagulls and the opportunity to visit the oldest property in the area.
Access to Nelson Bay Cave isn't child's play - a steep, stony path takes us from the road about 240m down the slope, surrounded by fynbos and the crashing waves below. A boardwalk and explanatory posters lead us towards a wide monster-mouth at the base of the cliff. The ominous feeling grows as we duck to avoid the rocky teeth and enter a huge, dim space. "Why didn't we bring torches?" we wonder, as we follow our guide deeper into the greenish gloom.
As our eyes adjust to the light, our disappointment lifts. We are stepping back into prehistory along a boardwalk which leads deep into the cave. Each step takes us thousands of years back in time until we descend to the lowest part - the rocky base of the original cave, where humans lived about 120000 years ago.
Our knowledge of those Middle Stone Age people has unfolded through archaeological excavation done here in the 1960s and 1970s by Ray Inskeep and Richard Klein. They have shown that Nelson Bay Cave was inhabited over a period of about 120000 years by Middle Stone Age and Later Stone Age people, ancestors of the Khoisan. The archaeologists carefully and methodically excavated the deposits in a portion of the cave, starting with the top (most recent) layers and working down deeper and deeper until they reached the bedrock below the oldest layer. They kept detailed records of each thing that they found.
At the end of the process, a brick-walled room was built to prevent the deeper layers from collapsing. A vertical glass window in the wall displays the whole depth of the excavation, and a solar-powered light enables us to see what was found at every level.
Our guide is Dr Janette Deacon, an archaeologist who, over 40 years, has studied the development of stone and bone tools in hundreds of Stone Age cave sites scattered all over the Western Cape. We are lucky to have her with us, bringing to life the story that has lain buried in the deep, dusty deposits of the cave.
She explains how archaeologists are able to put flesh on the fossilised bones, and to understand how people lived and thought by studying the things they left behind.
The deposits are a record of those who have used the cave and of the changing resources on which they depended. Those changes are a reflection of climate fluctuations over the millennia, and especially the rise and fall of sea level.
Between about 120000 and 50000 years ago, the story is revealed mainly by stone tools. Between 50000 and 18000 years ago, the cave was not inhabited by people. From about 18000 years ago, the human record resumes. The uninhabited period was during the peak of the last Ice Age: sea level was 130m lower than it is now, with all that water locked up in vast polar ice caps, and the coast was about 80km away. People would have looked out from the cave and seen giant buffalo, giant hartebeest and quagga grazing on plains which are now covered by the sea. The bones of these now-extinct four-legged dinners are preserved as fossils in the cave.
As the earth warmed, the polar ice caps melted and the sea level rose. The most dramatic evidence of this is the "sudden" appearance (within a few thousand years) of vast quantities of shells, fish bones and other seafood leftovers in the cave deposits. The most recent deposits are less than 2000 years old. The remains of sheep, cattle and pottery tell of Khoikhoi farmers who lived here.
The last inhabitants of Nelson Bay Cave could possible have been those who traded with the survivors of the São Gonçalo, wrecked in Plettenberg Bay in 1630.
The Portuguese traded with local herders while they spent nine months building two small boats from the wreckage, in which to sail away. Relics from their camp were discovered in 1979 and can be seen in the Plettenberg Bay municipal offices.
Disabled people are not able to reach the cave, and younger children would probably not appreciate what it has to offer. But there is a visitors' centre next to the parking lot, with a good display of artefacts from the cave and illustrated information posters.
The story that emerges from Nelson Bay Cave shows how climate change over thousands of years can change our environment. We are faced now by the threat of huge and drastic changes in the space of just a few years, caused by the actions of our own species. Do we have the foresight and ingenuity to save our world and ourselves?
Nonhlanhla Vilakazi is a PhD palaeo-herpetologist at Wits University. John Inglis is a consultant to Jive Media, an independent science communication agency. The tour of palaeontological sites was sponsored by the Department of Science and Technology (see www.saasta.ac.za). Read more about the trip on Nonhlanhla's blog:
Source: Times Live