300 - 900: Classic Mayan Age   Mayan society concentrates around great centers of civilization such as Tikal, Yazchilan and Palenque. During this period, the Mayans gain advanced understanding in the areas of medicine, mathematics, astronomy and architecture. For reasons not well known to anthropologists, these cities are suddenly abandoned around the year 900 AD. 900 - 1524: Post-Classic Era   The Mayan people disperse into different kingdoms throughout the Yucatan Peninsula and the highlands of Chiapas and Guatemala. These are divided into roughly thirty warring groups, of which today's 21 linguistic groups are the descendents.