Editing Collaboration (section)

===Trade===
Trade began in [[prehistoric]] times and continues because it benefits all of its participants. Prehistoric peoples bartered goods and services with each other without a modern currency. [[Peter Watson (business writer)|Peter Watson]] dates the [[History of international trade|history of long-distance commerce]] from [[Wiktionary:circa|circa]] 150,000 years ago.<ref>{{cite book | author=Watson, Peter | title=Ideas : A History of Thought and Invention from Fire to Freud | publisher=HarperCollins | year=2005| isbn=978-0-06-621064-3}} Introduction.</ref> Trade exists because different communities have a [[comparative advantage]] in the production of tradable goods.