EXP Milestones: your character has different milestones that are tracked and all reward you with a decent boost of growth. Things like distance travelled milestones, that if you walk 'x' miles you get some EXP. Then the milestone for that activity gets harder, requiring more distance travelled and so on. There could be milestones for quantity of food eaten or water drunk. Ones for specific types of food from player carcasses to roots. And ones who carnis for herbis killed. It could start out as 3 herbis killed, then move to 5, then 10, and so on.
I think that this would make growing your dinosaur much funner tracking these stats. It could also pave way for unique activities like one off milestones, like visiting all four corners of the maps (the locations closest to them that is) on the same dino.
Examples of possible additional milestones not mentioned above:
All food variations eaten (for your dino, one off)
Encounters survived (survive player combat with low HP)