Early humans were already using stone tips to enhance the killing power of spears at least 500 000 years ago, some 200 000 years earlier than previously thought, anthropologists said on Thursday.
Attaching stone points to spears - a technique known as "hafting" - requires more planning and effort than simply sharpening a stick, and was important in the development of early hunting weaponry.
Hafted spears are common finds at Stone Age archaeological sites dating as far back as 300,000 years ago, researchers said.
But this new study, published in the US journal "Science," showed that people were using the stone-tipped weapons much earlier.
"Although both Neanderthals and humans used stone-tipped spears, this is the first evidence that this technology originated prior to or near the divergence of these two species," said Benjamin Schoville, study coauthor from Arizona State University.
Lead author Jayne Wilkins, from the University of Toronto, added "it now looks like some of the traits that we associate with modern humans and our nearest relatives (the Neanderthals) can be traced further back in our lineage."
"This changes the way we think about early human adaptations and capacities before the origin of our own species," she added.
The stone spear points analyzed in this study were actually uncovered nearly 35 years ago, at a site near the edge of the Kalahari desert in southern Africa that is known as Kathu Pan 1.
In 2010, a team of researchers dated the stone points to 500 000 years ago, using optically stimulated luminescence and other methods.
The new study reports findings from an analysis of how these stone points were used, said co-author Kyle Brown, a skilled stone tool replicator from the University of Cape Town.
"When points are used as spear tips, there is a lot of damage that forms at the tip of the point, and large distinctive fractures form," he explained.
The ancient stone points show evidence of this kind of damage, offering proof they were used at the tip of spears and not for some other purpose.