Asia
The coastal periphery was home to some of the world's earliest known civilizations, each of them developing around fertile river valleys. The civilizations in Mesopotamia, the Indus Valley and the Yellow River shared many similarities. These civilizations may well have exchanged technologies and ideas such as mathematics and the wheel. Other innovations, such as writing, seem to have been developed individually in each area. Cities, states and empires developed in these lowlands.
History of slavery
Slavery was known in civilizations as old as Sumer, as well as in almost every other ancient civilization, including Ancient Egypt, Ancient China, the Akkadian Empire, Assyria, Babylonia, Ancient Iran, Ancient Greece, India, the Roman Empire, the Arab Islamic Caliphate and Sultanate, Nubia and the pre-Columbian civilizations of the Americas. Such institutions were a mixture of debt-slavery, punishment for crime, the enslavement of prisoners of war, child abandonment, and the birth of slave children to slaves.