Zapotec society in Mexico

The other article National Geographic has about the Zapotecs talks about the rise and fall of their civilization.  Most people have heard of the Aztecs, the Maya, and even the Olmecs (because of the giant heads) but few know about the Zapotecs.   The NG article sums them up:  For 1,500 years, the agrarian Zapotec state spanned 800 square miles (2,000 square kilometers) and was home to at least 100,000 people. The Zapotec were pioneers in the use of agriculture and writing systems. They were gifted weavers and ceramic artisans. They built Monte Albán, one of the earliest cities in the Americas, and established a remarkably organized bureaucratic structure.
U.S. archaeologists Gary Feinman and Linda Nicholas have been excavating an ancient city called El Palmillo, near Oaxaca, unraveling what happened to the once thriving center of 5,000 residents.  They have uncovered graves, palaces and a ball court but only have scant theories on what happened to El Palmillo or why it collapsed. 

(Photo source; screenprint of article)