The Mediterranean region contains the earliest archeological evidence of human use; the oldest known seeds date back to more than 5000 BCE in the Neolithic age with purposes such as food, anaesthetics, and ritual. Evidence from ancient Greece indicates that opium was consumed in several ways, including inhalation of vapors, suppositories, medical poultices, and as a combination with hemlock for suicide. The Sumerian, Assyrian, Egyptian, Indian, Minoan, Greek, Roman, Persian and Arab Empires all made widespread use of opium, which was the most potent form of pain relief then available, allowing ancient surgeons to perform prolonged surgical procedures. Opium is mentioned in the most important medical texts of the ancient world, including the Ebers Papyrus and the writings of Dioscorides, Galen, and Avicenna. Widespread medical use of unprocessed opium continued through the American Civil War before giving way to morphine and its successors, which could be injected at a precisely controlled dosage.