NO. 1 CULTURAL DEVELOPMENT IN LATIN AMERICA 29 
that there is one region which might well provide such data — the 
valley of the Motagua River, a desiccated, cactus-covered river plain 
between El Chayal and the Atlantic which has long been a rich hunt- 
ing ground for collectors of fossil elephants and other large Pleisto- 
cene fauna, but which has never been searched for remains of early 
man. Certainly there is no reason why kill sites of the sort that have 
been found at Santa Isabel Iztapan should not also be discovered in 
southeastern Mesoamerica, and it might be that habitation sites, miss- 
ing thus far in the Valley of Mexico, will be encountered here. 
The drastic climatic changes that brought to an end the Pleisto- 
cene Age, with its rich grasslands and large herds of herbivores, 
initiated the Hypsithermal Interval (Deevey and FHnt, 1957), be- 
ginning about 7000 b.c. and ending, in Mesoamerica, at least, around 
1500 B.C. Greatly elevated temperatures combined with decreased 
rainfall, ample evidence for which has been recovered from pollen 
cores from the Valley of Mexico examined by Sears (1953) and his 
colleagues, led to the disappearance of elephants and other mega- 
fauna in Mesoamerica and forced men into a collecting-type exist- 
ence — intensive and highly directed reliance upon more humble ani- 
mals such as deer and jackrabbits and upon plant foods, particularly 
seeds. Such a way of life has been documented by the researches of 
MacNeish (1958, 1961) in Tamaulipas, northeastern Mexico, and 
more recently in southern Puebla just beyond the borders of our area. 
It is now clear that in a context almost indistinguishable from the 
famous Desert Culture of the Great Basin country (Jennings, 1956, 
pp. 68-72; 1957, pp. 6-9), the Indians of Mesoamerica were begin- 
ning to tamper with the evolution of food plants at a very early date. 
This was the most important step ever taken by the native peoples of 
the New World, and it was taken for the first time either very near or 
in the zone in which we are interested. 
There is, of course, no wild form of maize {^Zea mays) in 
existence, and the locus of its domestication has been uncertain for 
many years. ^ The most recent evidence from Coxcatlan, and other rock 
shelters in the Valley of Tehuacan, Puebla, makes it certain that the 
food energy of maize was first captured by man between 5000 and 4000 
B.C. somewhere in the highlands of central or southeastern Mesoamerica 
— but not in the lowlands, since hardgrained grasses do not naturally 
occur in undisturbed tropical forests. Other cultigens, particularly 
^ The discussion that follows is based largely on Mangelsdorf (1958), Mac- 
Neish (1961), and on conversations with Professor Mangelsdorf and R. S. Mac- 
Neish. 
