What you'll need are 2 empty soda bottles (1 or 2 liter size), 2 wooden dowels (1/2" diameter, about 30" in length), Duct tape or cloth-backed adhesive tape, Newspaper (4-8 sheets), 4-6 brown paper lunch bags, Wide-tipped felt markers (black) and String or Bag of Flour

Before the party: Make "prehistoric boulders" by crumpling newspaper and stuffing 1-2 sheets into each lunch bag. Fold top of lunch bag over and tape bag closed with duct tape. Using felt-tip pen, make distinguishing marks on boulders for each team, e.g., small "o's" for one team and small "x's" for the other team.
Make the cave dweller "club" by placing one dowel in each soda bottle and taping dowel in place. Set up an obstacle course in party area, using existing shrubbery/trees and adding chairs, boxes and the like. Mark course with string or by dripping flour from bag.

During the Party: Divide children into two teams. Line up both teams at start/finish line. To start game, first player from each team uses the "club" to knock his/her team's "boulder" through course. (Remind children to hit only their own team's boulder.) Each player keeps hitting their boulder through the entire course in order to complete his/her turn through the course. The first team to finish the course, wins!
(Recommended age: 6 years and older)