During the entire period more than half of the population was concentrated in the Etla Arm of the Valley. This concentration was most evident during the earliest Tierras Largas Phase (See Fig. 1.2.1.) with the other two arms of the Valley, the Talacolula and the Zimatlán-Ocotlán becoming increasingly settled during the subsequent three phases. See San José Phase, Fig. 1.2.2; Guadalupe Phase, Fig. 1.2.3; and Rosario Phase, Fig. 1.2.4.
Settlements appear to have been located about 10 km apart (about a half-day’s walk) in well drained areas on extensions of the piedmont into the higher alluvium between the flood plain of the Rio Atoyac and the piedmont. Locations where the water table is near (average 2.5 m) the surface are most common. One might conjecture that access to arable land and potable water, as well as adequate drainage, played a role in choice of location. Not too surprisingly, these early occupations tend to be located near modern villages.
Today, the Rio Atoyac and many of its tributaries are ephemeral. In view of this fact, it would be interesting to examine proximity to ground water sources (springs and seeps) as a factor determining settlement location. To my knowledge, this has not been done.
The alluvial plain of the Rio Atoyac in the Etla Valley can, in normal years, produce two crop of maize each year. However, the aboriginal vegetation in the alluvium -- a fully developed tropical forest with trees as large as 2.5 m in diameter and 30 m tall spaced at 10-20 m, a dense, opaque canopy and relatively open understory in the flood plain merging into a mesquite thicket in the higher alluvium ( Smith '‘78) ---- would have presented formidable obstacles to slash-and-burn agriculture. It is not unlikely that early agriculture began in small flats in the piedmont barracas where clearing the vegetation would have been easier. It is not clear how much of the alluvium was actually under cultivation at this period.
