Once upon a time two tribes moved from the plains to the forest. In the forest were two giant trees. Trees so large an entire tribe could live in its follage. Since the tribes could not agree on how to govern together, they each took a tree for their own. Both tribes moved into their trees and over time forgot about each other.
Over the years the tribe in the northern tree would get up and over the corse of the day they would take turns bringing water from the river to the tree, they would prune the dead branches and families would move from the pruned branch to another, often sharing a branch until another grew strong enough to support a family. They would harvest what they needed as a tribe from the smaller trees around them and plant and nurture the surrounding forest to keep it plentiful.
The other tribe let families chose a branch for their own and none dared stand on another’s branch. They would harvest from the forest around the tree and build fences and walls to keep people away from their branch. If branches died, that wasn’t the problem of those who lived on healthy branches and they watched passively as families tumbled to the ground, knowing that it wasn’t their problem. They took care of their branch, and even built bigger and bigger supports with the wood they gathered from the forest, now bare beneath them. As their tree withered under the strain, they were unconcerned. As long as they protected their branch, who cared what happened to the tree. It wasn’t their job to haul water for everyone, only for themselves and their branch. They new that as they consumed more water, some of it would trickle down onto the roots without them having to check.
Over time one tribe was never seen again.