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.
Ancient history
The Zapotec emerged around 1500 years BC. They left behind the great city Monte Alban. Their writing system had been thought to have influenced the Olmecs but, with recent evidence, the Olmec may have been the first civilization in the area to develop a true writing system independently. At the present time, there is some debate as to whether or not Olmec symbols, dated to 650 BC, are actually a form of writing preceding the oldest Zapotec writing dated to about 500 BC.