From the article: 

"A similar process of an early state’s arising from warring chiefdoms has been described in the Oaxaca Valley of Mexico by Kent V. Flannery and Joyce Marcus, archaeologists at the University of Michigan. By 4,500 years ago, there were some 80 villages in the valley. As population increased, a period of intense warfare lasted from 2,450 to 2,000 years ago, culminating in the victory of one town over all the others in the valley and the formation of the Zapotec state.

"With the same process now documented in both North and South America, 'we are coming closer to having a model for pristine state formation that may have worldwide significance,' Dr. Marcus said. 'It also shows that our species, when thrust into almost identical circumstances, behaves in almost identical ways.'"

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