Tribes: It's 50,000 B.C. Where Are Your Children? — David Brin

In Tribes, the players are cave men and women. They hunt and gather food, make their tribal laws, and deal with natural disasters. But the object of the game is simple: Look after the children! In this game, the way to win is to have the most kids, and do whatever you have to do to make sure they survive to adulthood. The players must know when to cooperate, and when to cut their losses and protect their own families. Tribes supports 4 to 8 players, creating their own laws and social patterns. With several copies and a referee, it is possible to have several tribes playing at once, competing, trading, exchanging members, and even making war on each other.