In Life we do things for the sake of our benefit and survival ,according to our minds . But our hearts only wishes comfort and love, in the same time we are considered social animals so we invest our time and relationships in aspect of reciprocity .
Reciprocity is principle of doing a favour for someone in order for them to repay the favour with conscious intention and that was the Money of our ancestors, eventually it evolves with the years into trading before gold or silver were discovered so what they did is , giving handful of wood for lamp portion if the lamp owner need the meat if not, the wood owner has to find what the lamp owner need and get it !.After that era they discovered gold and silver and that was valuable to its rarity so it did ease life and start the trade with other nations upon they use it as currency. Currency has develop a lot since the time it discovered from stones of gold to coins and eventually to a new currency attached to other currencies . In the modern age money essential for survival, if you have no money or other source than yourself who aid you with it you can’t live unless the will of god if order has given from higher sky.
Trading comes from the social principle reciprocity witch is essential for life to survive and now a days a successful Trading happen when money exist in one of the parts of it .