Small stone blades found in a cave along a rugged stretch of South Africa's coast have pushed back by thousands of years evidence for persistent, advanced stone-toolmaking skills in early modern humans, according to a new study.
The results suggest that by 71,000 years ago, these people had long since developed the mental horsepower to tackle production problems and pass their manufacturing techniques to subsequent generations – a lot earlier than some researchers had thought.
Indeed, to some scientists the find supports the idea that mental abilities associated with modern humans emerged when anatomically modern humans did, about 200,000 years ago, rather than resulting from a genetic mutation cropping up between 40,000 and 50,000 years ago, as others have posited.
The evidence comes in the form of a large number of stone blades that average about one inch long. The blades were excavated from successive layers in soil deposits some 46 feet thick in a cave at Pinnacle Point, on the coast some 210 miles east of Cape Town. The deposits span some 18,000 years.
The oldest bladlets were found in a layer dated to 71,000 years ago and continued to appear in layers representing the ensuing 11,000 years. The same technique was used to prepare the parent stones throughout the period, but the designs evolved over time according to the international team reporting the results in Thursday's edition of the journal Nature.
Pinnacle Point boasts "a very impressive record" of advanced cognitive abilities in early modern humans at the time period the site covers, says Rick Potts, director of the human origins program at the Smithsonian Institution's Museum of Natural History in Washington.
Fleeting snapshots of such creativity appear in east Africa dating back far earlier, he explains. That creativity appears in the manufacture and use of pigments for symbolic and decorative purposes, groups separated by long distances exchanging raw materials, as well as shifts from hand axes to stone-tipped projectiles for hunting.
"You get things that fly through the air. The world has never been the same," he quips.
From disparate sites spanning different, far earlier periods than Pinnacle Point, the evidence suggests that "cognitive capacities and the social capacities had already evolved earlier on," he says. But invention can fizzle if populations are dispersed, making it hard for the innovation to spread, or the inventor gets eaten by some animal along the way as he heads home with his new invention.
The finds at Pinnacle Point, he suggests, highlight the role a persistent regional population with readily available shelter can play in perpetuating and improving a technology.
Pinnacle Point's blades required following some critical steps, according to the international team led by the University of Cape Town's Kyle Brown and Curtis Marean with Arizona State University's Institute of Human Origins.
People would have had to hunt for the right kind of rock, called silcrete. They would have to gather fuel for heat-treating the rock, a process that by then had been used for 91,000 years at the site. Then comes the preparation of cores from the rock, which would be shaped into blades, chipping to make the blades themselves, then reshaping them yet again. Then comes making the wood or bone handles or shafts that would become tools or weapons. Finally, the small blades would have to be affixed to the handles or shafts.
Maintaining know-how like this over an 11,000-year span, along with the skills needed to execute the various steps, would require accurate instructions to be handed down from generation to generation and over a fairly wide region, the team says.
These days, the ability to organize and perpetuate these skills over long periods and across a region would be dubbed "executive function," notes Sally McBrearty, a paleoanthropologist at the University of Connecticut in Storrs.
Executive function "is an essential component of the modern mind," she writes in an assessment for Nature that accompanied the new results from Pinnacle Point.
The tiny stone blades like those at Pinnacle Point could have affected the success modern humans had as they migrated out of Africa beginning a bit earlier than the oldest dates for the Pinnacle Point blades, she writes. The research team notes that the stone mini-blades could have been used as tips for arrows or spear-thrower darts – either of which have far greater range than a hand-thrown spear. That would allow hunters, or warriors, to operate at a safer distance from their targets.
If the migrants "were armed with the bow and arrow, they would have been more than a match for anything or anyone they met," Dr. McBrearty notes.