The problem here is that you are dealing with people who grew up in a trade based enviornment and recreate it. This doesn't mean that the "natural" state of humanity is trade or that trade is at all engraved in human nature. Presumably if you had a functioning communist society and took some people from it and put them into a capitalist society their instinctive reaction would be to create a miniature communist collective. That doesn't mean that communism is engraved in human nature, just that people recreate what they know.