Research showed that a delay of 1 ms in releasing a rock during a circular movement of the arm makes a 2 degree deviation. That's s why throwing a rock with a circular movement per hand or sling would not be that accurate. Some of you guys may be more accurate but it does not mean that sling is a user-friendly weapon if it comes to accuracy. Throwing sticks-hunting boomerangs have two advantages compared to sling: they spin in the air and cover a larger area like a shotgun. Deviations caused by bad timing in release is compensated. It makes the weapon more accurate for small game. Second advantage is the lift that the aerodynamic design provides. They flight straight unlike a rock, meaning better accuracy and momentum in longer distances. Even a rounded stone is one of the aerodynamically worst projectile as can be seen in firearms technologies. That the sling was invented by shephards makes more sense. Hitting wolfs or wild dogs from closer distances should have been easier.