Markets developed naturally. The Agora of Athens near the Parthenon was a famous marketplace. Socrates said, (or was it Aristotle?) that retailers or sellers of other people’s products on tables in markets contribute the least in social allocation of resources. Trading and bartering, rendezvous for fur traders, fishermen selling product in one place ashore, the souq of the Middle East (evidence exists of those existing in 500 B.C)., even the informal markets that developed about the temple that offended Jesus at Jerusalem…those are ancient practices.