I4U writes: "Once on land the player creature forms a pack and sets about making allies of other packs on the planet or destroying them to gain new parts to continue to evolve. As the pack grows, players can ally tribes and add members to their pack for fighting.
After all packs on the planet are extinct or allies of the player pack, the creature evolves to the tribal stage. The move from the pack stage to the tribal stage is the last point where the creature can be changed physically with the addition of parts or removal of them. The form the creature has going into the tribal stage is the form you live with for the remainder of the game."