At a rock shelter on a coastal cliff in South Africa, scientists have found an abundance of advanced stone hunting tools with a tale to tell of the evolving mind of early modern humans at least 71,000 years ago.
The discovery, reported in the current issue of the journal Nature, lends weight to the hypothesis that not only did anatomically modern Homo sapiens emerge in Africa but also, to a previously unsuspected extent, their cognitive capacity for abstract and creative thought and the conception of increasingly complex technologies associated with modern human behaviour.
The report describes the stone tools as microliths, thin blades about only an inch long that could be affixed to wood or bone. These tipped projectiles were either arrows propelled by bows or, more likely, spears launched by atlatls, wooden extensions of the throwing arm that act as a lever, imparting greater speeds and distances to the weapon.
This technology, the researchers said, may have been pivotal to the success of Homo sapiens as humans left Africa and entered Eurasia some 50,000 years ago, encountering Neanderthals who were limited to hand-thrown spears.
The new evidence appeared to answer some critics who have contended that previous findings of early modern human behaviour in Africa have been spotty and short-lived — a 'flickering' pattern of experimentation with little or no continuity over time and across regions.
The rock shelter excavations at Pinnacle Point, near Mossel Bay, east of Cape Town, show that this micro-blade technology continued over 11,000 years, until 60,000 years ago. The report says the technology was also "typically coupled to heat treatment" processes in shaping sharp and durable blades that persisted for nearly 100,000 years.
In their article in Nature, the researchers conclude, "Early modern humans in South Africa had the cognition to design and transmit at high fidelity these coupled recipe technologies."
One of the authors, Curtis W. Marean, director of the research and a paleoanthropologist at the Institute of Human Origins at Arizona State University, said, "Every time we excavate a new site in coastal South Africa with advanced field techniques, we discover new and surprising results that push back in time the evidence for uniquely human behaviour."
The lead author of the report was Kyle S. Brown, a specialist in ancient stone tools who is associated with the University of Cape Town. Prior investigations showed that this microlithic technology appeared briefly between 65,000 and 60,000 years ago and then seemed to vanish. Such thin blades had not been found in abundance until about 20,000 years ago.
Marean said that while some archaeologists were still skeptical of a strong African role in modern human behaviour, there was diminishing support for the more Eurocentric "creative explosion" concept, born of bedazzlement over the cave art and fine tools of Upper Paleolithic Europe, which became widespread after the arrival of modern humans.
"Ninety per cent of scientists are comfortable that fully modern humans and human cognition developed in Africa," Marean said. "Now they have moved on.
The questions are, how much earlier than 71,000 years did these behaviour emerge? Was it an accretionary process, or was it an abrupt event? Did these people have language by this time?"
Like many other archaeologists, Marean and his team have concentrated their investigations in the caves and rock shelters overlooking the Indian Ocean.
In a global ice age beginning 72,000 years ago, many Africans fled the continent's arid interior, heading for the more benign southern shore. Access to seafood and more plentiful plant and animal resources may have increased populations and encouraged technological advances, Marean said.