Making a point: wood- versus stone-tipped projectiles

What are the advantages of equipping a wooden arrow with stone, rather than just using the sharpened wooden tip? Very few it seems. In a series of well-controlled experiments the authors show that stone arrow-heads achieve barely 10 per cent extra penetration over wood. They then raise some pertinent ideas about the other advantages, social and symbolic that may have driven hunters the world over to adopt the stone tip.