- Broken Hippo apparently hasn't been hit by a rock recently!8-) I joke, but...
We're speaking of men holding rocks. You underestimate the effectiveness of rocks as weapons. Every man knows how to use a rock as a weapon and almost everyone has thrown a rock or pounded something with a rock. You needn't throw a rock to kill/harm someone; it's likely faster and easier if you keep the rock in your hand.
Rocks have been used as weapons since before prehistoric times. Rocks have possibly been instruments of death for more of our ancestors than have bullets.