Divide into two teams. Give 2 marbles to each team. Each team chooses 2 people to hide their marbles in their fists. Then the teams choose 2-4 people (depending on the size of the group) to defend their "goal". The people with the marbles want to get to the other teams goal without getting caught.
It wasn't all that long ago that we started fires, for heat and cooking, by rubbing sticks together. Believe it or not, there are people out there who actually teach us how to perform these simple skills, this is one of my friends who does just that.