It is supposed that the first tool that people (or near-people) used was to simply grab a hold of a rock and throw it, or use it to bash something in the head. Later, they learned to knap arrow points and then to assemble nuclear bombs. In the beginning rocks were plentiful and easy to use. They still are in some of the world’s hot spots.
If you make the target a game animal and if that animal starts moving about or try running away and you are hungry enough, the skill-set required can get pretty complex and requires lots of practice. Boys can and do practice and can get pretty good at it.
From watching professional sports, some boys may have figured out that by hurling things a great distance accurately they may eventually get big money and enjoy world-wide acclaim. Therefore, they never pass up an opportunity to try out the old arm. Unfortunately, the Park Rangers are obliged to remove these objects from the park’s lawns out of safety and aesthetic concerns as well as to protect our mower blades.
Little girls are another matter. They like to quietly gather together small piles of rocks in the pavilion or on the playground and leave them like peace offerings to the Park Rangers. These are accepted most graciously and, after a respectful amount of time has passed, when no one is looking, are repatriated to the parking lot.