Recently i have been thinking about an evolution type of mmo. Basically it goes like this:
The player doesnt just play 1 character but a family at the early stage of evolution of a planets life. You could say cavemen but the setting will not be earth. The player does start as either a male or female woman (there will be more than one race but lets stick to humans for now) but they can get 'married' and hence gain a spouse to also control, relatives, and then children etc
Basically nothing is invented yet, no magic has been discovered, no weaponry, no nothing. The game starts with the bare minimum, a player on the world, just like everyone else. Exploring the world they can find themsleves a crude home like a cave or try to errect a shelter.
They will no doubt 'discover' things and 'invent' things on the way. Whether that be by accident or by tinkering with several picked up materials. Magic can also be discovered in this way. Although anything dicovered will be the lowest denominator of the 'skill'. So for instance if someone made a weapon from wood, it would be a club. Later on, someoen might work out how to make a club with spikes or something like that, something slightly more advanced.
When an item, magic, or whatever is discovered or invented, then this is automatically logged as world lore. Hence the player creates the world lore by their actions.
Thats a very crude outline and leaves many questions.