The population of Monte Albán drops to about 4,000 with the Main Plaza essentially abandoned.
In contrast, population increases in the agriculturally less favorable Tlacolula Valley which now contains about half Valley’s population and in the Zimatlán-Ocotlán Valley.
During Monte Alba´n V, the population of the valley begins to grow again reaching an all-time high of 160,000 by the time of European contact. The Etla Valley is reoccupied and settlement is spread more uniformly across the entire valley than in earlier periods. More evidence of isolated households is present during this phase than in any other. One hypothesis that might explain this pattern is that families felt more “secure”. What social institutions could have provided this security?
Population growth comes to an abrupt halt at European contact. During the following century, population declines, (by how much is a matter of controversy) largely because of disease introduced by Europeans, and does not again reach pre-European levels until this century.
It is tempting to see yet another cycle in the abandonment and reoccupation of piedmont areas associated with the decline and resurgence of population in the IV-V phases. However, the settlement data does not unambiguously support this interpretation. During IV, settlement tends to be located in higher areas of the piedmont -- perhaps selected for defense against military attack. The alluvial plains appear to be very sparsely settled. Yet, this pattern is consistent with agriculture being largely confined to the alluvium (people traveling to the fields from fortified settlements?) and the agriculturally marginal piedmont remains unused -- as in earlier periods of lower population. During V, population growth is clearly associated with occupation (and presumably agricultural use) of the piedmont.
