14 INTRODUCTION
Figure A.5 Isthmus of Tehuantepec depression. Photograh by the authors of the text.highland zone of this area, composed of the Sierra Madre del Sur in Guerrero and
the Mesa del Sur in Oaxaca. In contrast to the Central Plateau, there are few large,
flat basins in this zone, which is instead covered by rugged mountain peaks and small,
deep valleys. The Valley of Oaxaca, the largest basin, supported dense populations
in the past and continues to do so today.
Much of the Central Plateau has been denuded of vegetation as a result of human
activities. Once the area was covered with evergreen and deciduous oak forests. At
higher elevations the mixed pine-oak forests gave way to stands of pines, firs, and ju-
nipers. At lower elevations grasses, scrub oak, cactus, acacia, and pirul (introduced
from Peru in the sixteenth century) now dominate. The southern part of the North-
ern Highlands, like the Central Plateau, once supported cloud-forest vegetation, and
in lower-lying arid valleys xerophytes (acacia and cacti) still predominate.
Neotropical (South American) fauna long ago invaded the Northern Highlands,
including small numbers of such mammals as the peccary, tapir, spider monkey,
jaguar, anteater, and armadillo. The Nearctic (North American) mammals native to
the highlands include white-tailed deer, rabbits, squirrels, cougars, and pumas. The
deer and peccary may have been the main mammals hunted and eaten in fairly large
numbers in aboriginal times by Mesoamericans living in the Northern Highlands. Mi-
gratory birds (ducks, geese, teals), amphibians (frogs, salamanders), and small fish
inhabited the many lakes of the Northern Highlands in times past, and were an im-
portant food source for aboriginal Mesoamericans.Southern Highlands. South of the Isthmus of Tehuantepec (Figure A.5) is a com-
plex highland area framed by two mountain chains, a geologically older northern chain
and a younger southern chain. The northern chain begins with the Chiapas plateau
and continues southeast as the Cuchumatanes and Alta Verapaz mountains of