Though not quite as rapid as the Early I population increase, this increase approaches the limits of natural growth rates for human populations, again suggesting immigration.
Most of the Valley’s population growth occured in second and third tier sites in the Tlacolula Valley to the east and the Zimatlán-Ocotlán Valley to the south while the central and southern parts of the Etla Valley experienced a decline in population. Population concentrations approaching 80% of that at Monte Albán appeared at Jalieza about 25 km southeast of Monte Albán Zimatlán-Ocotlán Valley and in the about 20 km to the east in the Tlacolula Valley including the site of Daínzú.
During Monte Albán IIIB, the total estimated population of the Valley declines again to about 65,000 while the estimated population of Monte Albán increases to its maximum of about 25,000 -- more than a third of that of the Valley.
In contrast to the population decline during Late I-II, which was accompanied by a growth of population at second tier population centers, the population decline in IIIB resulted in a concentration of population in and around Monte Albán . This concentration is accompanied by some population resurgence in the Etla Arm but decline and virtual abadonment of many parts of the Tlacolula Valley and Zimatlán-Ocotlán Valley. During IIIA as in Early I, most of the population growth occurs in the piedmont and lower elevations in the surrounding mountains (though this time further from the center of the Valley) exemplifying (for the second time) what Blanton, et. al. ( ‘93:86) refer to as the piedmont strategy. During IIIB, these areas are again abandonned, just as they were in Late I-II. When population increases people tend increasingly to occupy the less productve piedmont lands. When population declines, these lands are abandoned. We have already considered alternaive explanations for this.
