<Table> <Tr> <Td> Part of a series on </Td> </Tr> <Tr> <Th> World trade </Th> </Tr> <Tr> <Td> </Td> </Tr> <Tr> <Td> Policy (show) <Ul> <Li> Import </Li> <Li> Export </Li> <Li> Balance of trade </Li> <Li> Trade law </Li> <Li> Trade pact </Li> <Li> Trade bloc </Li> <Li> Trade creation </Li> <Li> Trade diversion </Li> <Li> Export orientation </Li> <Li> Import substitution </Li> <Li> Trade finance </Li> <Li> Trade facilitation </Li> <Li> Trade route </Li> <Li> Domestic trade </Li> <Li> Tax, tariff and trade </Li> </Ul> </Td> </Tr> <Tr> <Td> Restrictions (show) <Ul> <Li> Trade barriers </Li> <Li> Tariffs </Li> <Li> Non-tariff barriers </Li> <Li> Import quotas </Li> <Li> Tariff - rate quotas </Li> <Li> Quota share </Li> <Li> Import licenses </Li> <Li> Customs duties </Li> <Li> Export subsidies </Li> <Li> Technical barriers </Li> <Li> Bribery </Li> <Li> Exchange rate controls </Li> <Li> Embargo </Li> <Li> Safeguards </Li> <Li> Countervailing duties </Li> <Li> Anti-dumping duties </Li> <Li> Voluntary export restraints </Li> </Ul> </Td> </Tr> <Tr> <Td> History (show) <Ul> <Li> Mercantilism </Li> <Li> Protectionism </Li> <Li> Laissez - faire </Li> <Li> Free trade </Li> <Li> Economic nationalism </Li> <Li> Economic integration </Li> </Ul> </Td> </Tr> <Tr> <Td> Organizations (show) <Ul> <Li> International Monetary Fund </Li> <Li> International Trade Centre </Li> <Li> World Trade Organization </Li> <Li> World Customs Organization </Li> </Ul> </Td> </Tr> <Tr> <Td> Economic integration (show) <Ul> <Li> Preferential trading area </Li> <Li> Free trade area </Li> <Li> Customs union </Li> <Li> Single market </Li> <Li> Economic union </Li> <Li> Monetary union </Li> <Li> Fiscal union </Li> <Li> Customs and monetary union </Li> <Li> Economic and monetary union </Li> </Ul> </Td> </Tr> <Tr> <Td> Issues (show) <Ul> <Li> Intellectual property rights </Li> <Li> Smuggling </Li> <Li> Competition policy </Li> <Li> Government procurement </Li> <Li> Outsourcing </Li> <Li> Globalization </Li> <Li> Fair trade </Li> <Li> Trade justice </Li> <Li> Emissions trading </Li> <Li> Trade sanctions </Li> <Li> War <Ul> <Li> Currency </Li> <Li> Trade costs </Li> <Li> Customs </Li> <Li> Trade </Li> </Ul> </Li> <Li> Trade and development </Li> </Ul> </Td> </Tr> <Tr> <Td> Lists (show) <Ul> <Li> Imports </Li> <Li> Exports </Li> <Li> Tariffs </Li> <Li> Largest consumer markets </Li> <Li> Leading trade partners </Li> </Ul> </Td> </Tr> <Tr> <Td> By country (show) <Ul> <Li> Trade mission </Li> <Li> Trading nation </Li> <Li> United States </Li> <Li> Argentina </Li> <Li> Pakistan </Li> <Li> Romania </Li> <Li> Vietnam </Li> <Li> India </Li> </Ul> </Td> </Tr> <Tr> <Td> Theory (show) <Ul> <Li> Comparative advantage </Li> <Li> Competitive advantage </Li> <Li> Heckscher--Ohlin model </Li> <Li> New trade theory </Li> <Li> Economic geography </Li> <Li> Intra-industry trade </Li> <Li> Gravity model of trade </Li> <Li> Ricardian trade theories </Li> <Li> Balassa--Samuelson effect </Li> <Li> Linder hypothesis </Li> <Li> Leontief paradox </Li> <Li> Lerner symmetry theorem </Li> <Li> Terms of trade </Li> </Ul> </Td> </Tr> <Tr> <Td> <Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> </Td> </Tr> </Table> <Tr> <Td> Part of a series on </Td> </Tr> <Tr> <Th> World trade </Th> </Tr> <Tr> <Td> Policy (show) <Ul> <Li> Import </Li> <Li> Export </Li> <Li> Balance of trade </Li> <Li> Trade law </Li> <Li> Trade pact </Li> <Li> Trade bloc </Li> <Li> Trade creation </Li> <Li> Trade diversion </Li> <Li> Export orientation </Li> <Li> Import substitution </Li> <Li> Trade finance </Li> <Li> Trade facilitation </Li> <Li> Trade route </Li> <Li> Domestic trade </Li> <Li> Tax, tariff and trade </Li> </Ul> </Td> </Tr>

Who helped isolated civilizations trade with one another in ancient times