November 7, 2012 | 8
Archaeologists excavating a cave on the southern coast of South Africa have recovered remains of the oldest known complex* projectile weapons. The tiny stone blades, which were probably affixed to wooden shafts for use as arrows, date to 71,000 years ago and represent a sophisticated technological tradition that endured for thousands of years. The discovery bears on an abiding question about when and how modern human cognition emerged, and suggests a way by which early modern Homo sapiens outcompeted Neandertals to eventually become the last human species standing.
Fossils show that humans who basically looked like us had evolved by around 200,000 years ago. Yet based on the cultural stuff they left behind, it looked as though anatomically modern humans didn’t begin thinking like us until much later. And when the creative spark did eventually ignite, the flame flickered only briefly before fizzling, only to spark and fade again and again as populations died out, taking their innovations to the grave. Complex projectile weapon technology, for example, seemed to make a brief first appearance sometime between 65,000 and 60,000 years ago and didn’t stick until after 40,000 years ago. But whether this flickering pattern in the archaeological record is real or merely an artifact of the small number of sites excavated has been unclear. The new South African finds, which come from a site called Pinnacle Point 5 – 6 (PP5-6), support the latter scenario.
Archaeologists have often focused on symbolic remains—from body ornaments, such as beads, to engravings and paintings on cave walls—in their search for clues to the origin of the modern mind. The idea being that this symbolic stuff is a good indicator that whoever made it had language, a hallmark of modern human cognition. In a paper detailing their discovery published in the November 8 Nature, Kyle S. Brown of the University of Cape Town, Curtis W. Marean of Arizona State University and their colleagues make the case that the advanced technology represented by the tiny stone blades they found at PP5-6 is also a proxy for complex cognition. (Scientific American is part of Nature Publishing Group.)
To craft the stone points, the people at PP5-6 first had to locate and collect a specific type of stone called silcrete. They then had to gather wood and transport it to a designated spot to build a fire to treat the stone, heating it to just the right temperature to make it easier to shape. After carefully chipping away at the rock to form tiny, sharp blades, they made mounts for the blades from wood or bone, and joined the stone to the mounts with mastic to create composite tools in the form of arrows or darts. The persistence of such a complex projectile technology for 11,000 years at PP5-6 (and the persistence of heat treatment of stone for 100,000 years at Pinnacle Point, which previous research documented) implies that people across a large region were using it and transmitting the recipe from one generation to the next verbally, according to the researchers.
“These operations would no doubt have taken place over the course of days, weeks or months, and would have been interrupted by attention to unrelated, more urgent tasks,” observes paleoanthropologist Sally McBrearty of the University of Connecticut in a commentary accompanying the team’s report. “The ability to hold and manipulate operations and images of objects in memory, and to execute goal-directed procedures over space and time, is termed executive function and is an essential component of the modern mind,” she explains.
McBrearty, who has long argued that modern cognitive capacity evolved at the same time as modern anatomy, with various elements of modern behavior emerging gradually over the subsequent millennia, says the new study supports her hypothesis. A competing hypothesis, advanced by Richard Klein of Stanford University, holds that modern human behavior only arose 50,000 to 40,000 years ago, as a result of some kind of fortuitous genetic mutation that kicked our ancestors’ creativity into high gear. But discoveries of symbolic items much older than that supposed mutation–and older than the PP5-6 arrowheads for that matter–have cast doubt on Klein’s theory. And other finds hint that Neandertals, too, engaged in symbolic behaviors, which would suggest that the capacity for symbolic thinking arose in our common ancestor perhaps half a million years ago.
Brown and his collaborators conclude by noting that this projectile technology, which allows one to attack from a safe distance, would have given modern humans a significant edge during hunting and interpersonal conflict as they spread out of Africa into Europe and encountered the resident Neandertals equipped with handheld spears. McBrearty agrees, writing, “if they were armed with the bow and arrow, they would have been more than a match for anything or anyone they met.”
*Updated 10/08/12 at 2:00 p.m. to specify that the newly discovered artifacts are the oldest remains of complex projectiles as opposed to simple ones, such as hand-cast spears.