Normal battle
When you are using your 3 daily battle actions to attack another caveman, these are the potential results for the attacker:
Win: 40 XP +/- difference in caveman levels (+ if you are lower level, - if higher level)
Lose: 10 XP +/- difference in caveman levels
Passive battle
You can also be attacked while online/offline (if your battle mode is on). You may be attacked by other cavemen up to 3 times a day, but you will gain less XP than normal battle.
Level requirements in XP, per level:
Each caveman gathers XP in order to level up, and each level has a specific requirement in XP.
There are 30 levels in total: Level 1 is 50, level 30 is 1500. Each level's requirement is increased by 50 XP.
Level 1: 50
Level 2: 100
Level 3: 150
Level 4: 200
Level 5: 250
…
Level 28: 1400
Level 29: 1450