Colonization and microevolution in Formative Oaxaca, Mexico

Abstract

Linguistic evidence indicates that the Zapotecan languages spread from the Central Valleys of Oaxaca to the southwest during the Middle and Late Formative (800 BC‐AD 250), and to the north and east during the Classic and Postclassic (AD 250–1521). The archaeological record of the lower Río Verde Valley, on the western coast of Oaxaca, supports this model of linguistic differentiation. The earliest significant settlement in the valley dates to the late Middle Formative, and this population probably spoke an ancestral form of Chatino, a Zapotecan language. Cranial non‐metric and odontometric analyses of biological distance demonstrate that the skeletal remains from the Verde are more similar to those from the Early and Middle Formative Valley of Oaxaca than to those from the Late Formative Mixteca Alta and Valley of Oaxaca. This follows the predictions of the model of linguistic divergence. Despite this similarity, the teeth of the coastal series are dramatically smaller than those of any highland sample. This suggests rapid adaptation in response to the different selective pressures exerted by the lowland environment.