28 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 146 
gions at all times. Quite obviously, the profound climatic changes 
which have taken place in the Northern Hemisphere since the final 
advance of the Wisconsin glaciation have altered some ecological 
zones quite drastically. For instance, with only a little less rainfall 
than today, most of the Peten of northern Guatemala would be un- 
inhabitable for either hunters or farmers, owing to the scarcity of 
drinking water in the dry season. Such a drastic lowering of precipi- 
tation probably occurred several times in the history of the Peten. On 
the other hand, the invention or adoption of certain important tech- 
niques such as plant domestication might have "pre-adapted" popu- 
lations to occupy new ecological niches which had been denied to 
them previously. We will examine such possibilities later. 
Keeping in mind these three factors — highland-lowland contrast, 
possibilities of easy communication or lack of same, and fluctuating 
environmental potentials — let us now consider the broad outhne of 
cultural evolution in southeastern Mesoamerica as it is presently 
known. This evolution has been seen in terms of five great periods: 
Early Hunters, Archaic, Formative, Classic, and Post-Classic (fig. 
5). It will be clear, however, that these are to be considered only as 
constructs which are subject to change at any time. 
Of the Early Hunters Period, very little can be said. The general 
absence of recorded sites pertaining to the hunting and gathering 
peoples of the terminal Pleistocene in southern Mesoamerica can 
only be laid to the failure of archeologists here to take much interest 
in the problem. It is true that the density of vegetation in both high- 
lands and lowlands has discouraged search, but the find of a Clovis 
point of obsidian near San Rafael (Coe, 1960a), not far from Guate- 
mala City, indicates the possibility of finding early occupation all 
over the region. The workshop site of El Chayal (fig. 3), for instance, 
located only 26 kilometers northeast of Guatemala City, covers at least 
5 acres and consists of hundreds of thousands of obsidian artifacts 
and waste flakes, not one of which can surely be ascribed to the 
Formative or any later period. The stemmed and lanceolate points 
and the single-shouldered knives which have been collected at El 
Chayal suggest an affiliation with South American preceramic cul- 
tures such as Ayampitin, Viscachani, and El Jobo. It may well be 
that in southeastern Mesoamerica, or at least in Guatemala, two an- 
cient traditions met, one from North America with fluted points, and 
the other pan-continental with lanceolate points, huge percussion- 
chipped flakes and blades, and heavy choppers. 
Unfortunately, we have for these scanty and scattered finds neither 
firm dating nor faunal association. It might be pointed out, however, 
