Stone spear points 'life-changing'
Stone spear points were the equivalent of hollow-nosed bullets to prehistoric hunters living 500,000 years ago, new research suggests.
Scientists who tested stone-tipped and sharpened wooden spears found that both had the same penetrating power.
But like the hollow-nose or "dum-dum" bullet, the stone point caused far more damage.
Thrust into gelatin, the stone-tipped spears created a significantly larger and wider "wound" cavity.
In the same way, hollow-nosed bullets that expand on impact are more destructive than regular bullets.
Researcher Dr Jane Wilkins, from Arizona State University in the US, said: "Hafting a stone point to the end of a spear was an important innovation that changed life for Pleistocene humans.
"Humans with stone-tipped spears were more likely to kill the game that they targeted, and were able to secure high quality food resources more frequently and regularly."
The study involved shooting six stone-tipped and six sharpened wooden spears into gelatin and examining the degree of penetration and damage they produced.
All were fired from a cross-bow with the same amount of force.
Up-grading spears with stone tips may have had a major impact on human evolution, said scientists writing in the online journal Public Library of Science ONE.
It took time and effort to prepare and assemble a spear with a stone tip, the researchers stressed.
Stone tips also broke more frequently than sharpened wooden points - which could be dangerous when faced with a large angry animal.
Yet our ancestors seemed convinced that stone-tipped spears were a good idea.
Co-author Benjamin Schoville, also from Arizona State University, said: "Putting a fragile stone tip on a spear is risky, but we show that there are serious rewards in terms of both the size and shape of the wound created that made this innovation extremely worthwhile during our evolution."