Welcome to the tribal stage!   You will first start off doing a camera tutorial.  After that, you will need to collect some food.  And then another tribe will appear.  You will either be nice to them or be mean to them.  You can upgrade your tribe by being nice to other tribes or killing them.  You can get new weapons for killing, or you'll get musical instruments to make friends with other tribes.  If you stay in the middle for the other stages you can get friends on your team.  After you have defeated or became friends with all of the other tribes, you will advance to the civilization stage.