The Stone axe is a partial consequence weapon that will become your default weapon if your creature is a carnivore in tribal stage. Note that this does not mean the carnivore trait from the cell stage, but as an actual diet. As a melee weapon, it deals great damage to enemy tribe members and wild animals, but is weaker against tool shacks and huts.
Clicking the "Axe" button on the bottom of the screen will make tribe members whirl around and damage any enemy that comes near. A good tactic to use is by equipping stone axes and eliminating all enemy tribe members before destroying the main hut. Once all the enemy tribe members are eradicated, equip fire torches back to the village and return to destroy the main hut if possible.