Wealth in a nutshell according to my views. What I think you're missing is that trade need not be limited to necessities. Why not use your surplus to buy that nice shiny rock the neighboring tribe has found? — Echarmion
I do believe that shiny rocks became a thing way after the concept of trade and wealth. After all, there was no other way to store value or divide assets. How else can you trade 7 chickens for one cow?
Kill the cow and left 1/2 of it to rot is not a good business model.
Salt was also a thing to store value but I could see mischievous children destroying stored wealth with water.