Writing & Calculation: The Maya invented a writing system of hieroglyphs. They also invented a number system with a base "20". For example the number five was a bar and the numbers one to four were represented by a dot. Moving the symbols to a higher position changed the value by twenty.

Here is a report on the THe Mayan Calendar from a site which contains information on Mesoamerican cultures..

Communication and Trade: The Mayas were great traders. They traded between other city states in their areas. By the time the Spanish arrived they were no longer trading in large areas. There had been a lot of warfare among the Maya even before the Spanish arrived.

Here is a timeline of THe Mayan Civilization with some explanation of the major historical periods.

The Decline of the Maya Civlization Before the arrival of the Spanish many Mayas had already abandoned their cities--perhaps because of food shortage or perhaps because of warfare. The southern part of the Yucatan showed the decline in city populations first. The Maya city states stopped trading with each other and declared war on one another.