This design is something between a fantastic RPG, a strategy game and an experience.
It’s a RPG in the sense you’ll be taking the role of the Ruler that must deal with creatures in a world where everything is evolving: in your generation, people may not know how to forge metal, but in the next your people will be forging swords, and the next they may be learning how to use magic… but at the same time, creatures are also evolving: goblins will learn how to create weapons with sticks and stones, trolls will begin to develop some primitive thinking, snakes may grow until they become new monsters…
It’s a strategy game in the sense you must give orders for your people, it they should hunt, and if they do what should they hunt, if they must develop their technology or if they should look for alliances. As the game is for mobile, I don’t think about having a huge strategy aspect in it, people can look for themselves.
To finish, about the whole experience thing, it would be a commentary on evolution and your relationship with other creatures. Yes, hunting rabbits may be the easiest way to get food, but if they are extinct, creatures like goblins may need to change their prey to farmers that live nearby. And having the whole evolution theme, the player should, sometime, ask if he truly have the right to kill a whole race only because they are not humans: of course, you wouldn’t suddenly be allies with the goblins, you would need to have certain technologies and fulfill some requisites, but you can do it.