Intelligence is meta-adaptation - adaptation that allows you to adapt to environment changes on the fly (without wasting many generations for mutation and selec

Intelligence is meta-adaptation - adaptation that allows you to adapt to environment changes on the fly (without wasting many generations for mutation and selection). So, the evolutionary pressure must have been something that required adaptation within one generation - for hundreds of generations. If the need for adaptation was a single big event - brains wouldn't have the time to evolve - it would be easier to adapt directly. You don't need human-level intelligence to hunt big prey nor small prey. The changes must have been frequent enough to be worth wasting calories on bigger and bigger brains and supporting them through the time when there were no changes to adapt to. So I don't think overhunting was it. Every predator species deals with overhunting.