Palaeoclimate records from marine sediment and ice cores suggest that around the time the Still Bay culture disappeared, global temperatures dropped and the polar ice sheets grew.
Ocean levels fell, and the Still Bay people may have followed the sea onto the continental shelf, which would have become a productive plain.
Next come shells from local mussels and snails amid blackened soil and bits of charred wood, all remnants of an ancient feast.
It was one of many enjoyed by a distinct group of early humans who visited Blombos Cave over the course of thousands of years.
What drove the coming and going of these early cultures?
At about the time the Still Bay culture disappeared, the globe — already in the middle of a glacial period — began to cool even further, causing sea levels to fall (see 'Crucible of culture').
“If we can get some good climatic data, we can at least hazard some guesses.” Outside the cave, a cool November breeze scours the steep slope to the shore, which Henshilwood has known since he was a child.
His grandfather bought this land on the Southern Cape as a fishing retreat in 1961 and Henshilwood spent his holidays searching the hills and caves for ancient artefacts.
Only in 1997 did he secure funding for a full excavation from the US National Science Foundation.
Hundreds of steel tabs mark strata on vertical walls of sediment.
While Henshilwood works on the cave's top layer, from 72,000 years ago, his partner and co-excavator, Karen van Niekerk, sifts through the bottom strata of sediments, which are roughly 100,000 years old.
Metal scrapes on hard sand as archaeologist Chris Henshilwood shaves away the top layer of sediment in Blombos Cave.
After just a few moments, the tip of his trowel unearths the humerus of a pint-sized tortoise that walked the Southern Cape of South Africa many millennia ago.