Charlton (1973) argues that Parsons' (1969, 1970) explanation for the abandonment of the central Texcoco region, Mexico, during the Early Toltec period, is misleading because Parsons considered only “non-ecological” factors. Specifically, Parsons suggested that this zone was not occupied because it was the boundary between the political spheres of two competing regional centers, Tula and Cholula. Charlton argues instead, that the region was abandoned due to “ecological” factors. Namely, he argues, the Early Toltec period was a period of low population density, when only the most suitable agricultural land was occupied; thus the central Texcoco region was not utilized because it is agriculturally marginal. Charlton’s emphasis on the use of “ecological” factors to explain the distribution of Early Toltec settlements is misleading because it does not allow prediction of the locations of other known Early Toltec settlements in the Valley of Mexico. Abandonment of large portions of the Valley of Mexico was a general pattern during this period, due to “Balkanization” and competition between local centers.