1) date to 6,200 years ago and reinvigorate support for a model in which groups living in the Southern Highlands had already domesticated maize by 6,000–7,000 years ago and later diffused its cultivation to groups living at lower elevations in the valley of the Balsas River and coastal lowlands (4).
Methodologically, sedimentary pollen and other microfossil sequences can make valuable contributions to reconstructing the geography of early maize cultivation, but we must acknowledge the limits to precision that bioturbation in coastal lagoons imposes on the dating of such records. But much disagreement remains concerning the mechanism, location, and timing of the domestication process and, therefore, its relationship to Mesoamerican social and environmental processes, such as the inception of sedentism and deforestation.
(A) Maize pollen grain from the 515-cm level taken by scanning electron microscopy at ×1,000 magnification.
(B) Top edge of grain shown in A at ×10,000 magnification.
Vestiges of sloping-field terraces mark the piedmont west of the coastal plain; their precise chronology remains unknown, but Postclassic (A. 900-1519) peoples probably used them for cotton and maize cropping (15).
Maize pollen occurs in the Veracruz core beginning at a depth of 515 cm, with 14 grains with diameters of 59–94 μm (mean, 77 μm) (Fig. That diameter range is diagnostic for Mexican landraces, and the spinule density of 6–7 per μm also conforms to that of maize (16) (Fig. Further confirming the inception of maize cultivation at that level, the pollen spectrum displays indicators of forest clearance and cultivation: a decrease in tropical trees and parallel increases in weeds and grasses (Fig. The bulk of the grass pollen count belongs to a population of grains with diameters of Maize pollen grains from core.