The Black Sea was once part of a larger body that included the Caspian and Aral seas. In the Tertiary period, it was separated from the Caspian Sea and was linked to the Mediterranean Sea. Evidence suggests that more recently, about 7,600 years ago, at the end of a long dry period, it was flooded when the Mediterranean, having again become separate, broke through at the Bosporus, an event that may have scattered farmers from its shores into Europe and Asia. Some scientists have hypothesized that this event happened catastrophically and is the source of the biblical story of the Deluge.
The Pontus Euxinus [hospitable sea] of the ancients, the Black Sea was navigated and its shores colonized by the Greeks (8th–6th cent. B.C.) and later by the Romans (3d–1st cent. B.C.). Its importance increased with the founding of Constantinople (A.D. 330). In the 13th cent. the Genoese established colonies on the Black Sea, and from the 15th to the 18th cent. it was a Turkish "lake." The rise of Russia led to protracted dispute with the Ottoman Empire over control and use of the Bosporus and Dardanelles. In 1783, Russia annexed the Tatar Khanate of Crimea, which blocked its access to the sea, but the Treaty of Paris, which ended the Crimean War of 1856, frustrated Russia's expansionist ambitions, and Russia and its successor, the Soviet Union, retained limited influence in the region. In 1992, after the breakup of the Soviet Union, the Black Sea Economic Cooperation was established by nations surrounding the sea (not all members actually border the sea); it became a formal international organization in 1998. The six nations bordering the sea established the Black Sea Naval Cooperation Task Group in 2001 to promote cooperation on naval and environmental issues.