With and expanding population and limited land to support it,they had a choice of either conquest or trade. They selected trade,and in pre-mechanical transport era, the only economical means wasshipping.To engage in long distance shipment they had to invent astralnavigation to be able to sail directly rather than huggingCoastlines. These gave them a clear edge in establishing theirtrading empire.And their trade became largely 'carry trade' shipping productsbetween other places and making a good profit on the buying andselling of the goods and slaves they transported around theMediterranean Sea.