Johny SYSEL/Wikimedia Commons

This coin reveals when Rome became an empire

When did Rome become an empire? Its coins hold a clue. Rome controlled only territory in Italy until 209 B.C.E., when it gained command over the Iberian Peninsula—which includes Spain and Portugal—during the Second Punic War against Carthage. Before the war, which featured Hannibal and his famous elephants, lead isotopes in Roman coins corresponded to sources of silver around Greece and Italy, researchers report today at the Goldschmidt Conference, which focuses on geochemistry, in Paris. After the war, however, Roman coins (like the one above) match the signature of the silver mines in the Iberian Peninsula. The conquest of Iberia was Rome’s first major expansion beyond Italy, minting its status as an empire.