The natural state seems like people taking from outsiders and sharing amung their inner circle. Capitalism needs a lot of outside influence to keep going.
I used my resources to produce more resources, you did too, and we exchanged in a way we both considered to be in our best interest (Or we wouldn't have done it).
If I'm way off base I'd love to hear.
Lots of societies have free trade that I don't think would be usefully described as "capitalist." (And anecdotally societies in which free trade is discouraged seem to end up with a lot of black market free trade activity -- it is just too powerful an attractor.)
To me capitalism is a more descriptive of a narrower and more modern development. Free trade is an aspect of it, but not sufficient to describe it.