Chapter 2

Humans and Environment in the Americas

               The human presence in the Americas most likely began some 30,000 years ago with the advance of hunters across the Bering land-bridge from northeast Asia into Alaska. By 23,000 B.C. they were seeking shelter in caves in western Nevada, and by 15,000 B.C. they were hunting woolly mammoths in the marshes of the Mexican plateau. Certainly by 10,000 B.C. their descendants had occupied much of South America, and a few millennia later had reached even the remotest outliers of Tierra del Fuego.

               This 30,000-km (20,000-mi), 20,000-year trek was the epic of hundreds of generations. Through this vast expanse of space these peoples of Mongoloid origin had encountered environments ranging from polar to tropical, from desert to rain forest, from featureless alluvial plains to lofty volcanic peaks. And during this vast expanse of time, they had experienced the disappearance not only of the great ice sheets but also of many of the larger game animals adapted to the glacier's fringes, followed by a marked warming of the climate and a rising of sea levels. Thus, although their sustenance had initially depended almost exclusively on their fortune as hunters, whether on land or in the adjacent coastal waters, as they advanced into the warmer, more vegetated regions of the Americas their diet increasingly came to embrace edible plants as well. Their economy was essentially one of "collecting" -- that is, living off whatever animals, fish, or birds they could kill and gathering whatever roots, berries, or fruits they could find. Yet, even under these circumstances they were quick to realize that "all places were not created equal," for some regions afforded them a bounty of foodstuffs whereas others were niggardly in the extreme.

               About the time that the first hunters and gatherers were reaching the southernmost outposts of the Americas (i.e., ca. 7000 B.C.), peoples in the Amazon basin, the foothills of the central Andes, and the mountains of southern Mexico and Guatemala were beginning to modify the environments of certain of the food plants which they had come to favor. At first, these modifications entailed little more than plucking away competing, unwanted vegetation or supplying water to a desired plant in time of drought. Gradually it likewise came to involve consciously selecting and planting seeds in areas that had been specially prepared to receive them. Thus, from such humble origins evolved the process of plant domestication which we term "agriculture" -- or perhaps more properly "horticulture," because of its initial gardenlike scale. Certainly, for the early peoples of the Americas this was no "revolution," but rather a painfully slow evolution which saw the proportion of their diet based on domesticated plants increase from some 10 percent about 5000 B.C. to just over 35 percent about 1500 B.C. (MacNeish, 1964, 531-537). Chief among the plants which were being cultivated relatively early in the Mesoamerican region were squashes, chile peppers, avocados, beans, and amaranth, with maize making its initial appearance as a cultigen sometime around 3000 B.C. (Long et al., 1989).

               Because of the overwhelming importance of maize to the subsequent development of civilization in Mesoamerica, a brief recapitulation of the history of its domestication is in order. Through the researches of Paul Mangelsdorf and his associates, the transition of what was a singularly unpromising plant, whose initial cob was no larger than a thumbnail, to the large golden-eared type of grain we know today, has been meticulously traced. Wild forms of maize grew both in Mesoamerica and along the west coast of South America in Peru and Ecuador. Somehow -- most likely, it would seem, through the human agency of trade -- the primitive domesticate from Mesoamerica. was crossed with its counterpart in South America, resulting in a genetically improved form of corn which was crossed again with an Andean grass known as tripsacum. This second crossing resulted in a much altered and enlarged ear of corn which, when traded back to Mesoamerica, crossed a third time with a native grass of the Mexican highlands called teosinte. From this union a further explosive increase in size took place, resulting in the whole spectrum of maize types found throughout the region today. It was from these, in turn, that the modern hybrids we are familiar with in the North American Corn Belt were derived (Mangelsdorf, 1983).

               The beginnings of agriculture, slow and uneven as they were, nevertheless had a profound geographic significance. For the first time in human history, the natural world had been divided by a cultural dichotomy: Unlike hunting and gathering, which could be practiced everywhere, agriculture was possible in some areas but not in others. Although the specific parameters of given plants were certainly not understood at the outset, by trial and error would-be farmers found that there were spatial limits to where they could grow their crops of choice. In a tropical setting, adequate warmth was scarcely a concern, but adequate moisture, at the appropriate time, definitely was. Differences in drainage, exposure, and productivity of the soil were no doubt observed but probably not identified as factors of consequence in their own right.

               In North America, the most critical cultural boundary demarcating the hunting-and-gathering cultures from the agricultural cultures was the climatic limit of maize, or corn, cultivation. (In South America, on the other hand, the potato permitted the expansion of cultivation into regions far cooler than those in which corn would ripen.) Where maize would grow, a people could become farmers; where it would not, they were destined to continue to subsist as hunters and gatherers. This was not a matter of human will, intelligence, or energy; it was a decree of nature which not even the most determined, dedicated, or capable individual could defy. In northeastern North America, where warmth was the limiting factor, the Iroquois of central New York state could and did become maize farmers, whereas the Algonkians, farther north in the St. Lawrence Valley, could not grow corn and thus were denied that option. In the American tropics, the limiting factor was moisture, and in the south and east of Mexico where the rains were adequate to nurture maize, farming societies developed and throve, whereas on the plateau in the north and west, only nomadic collecting was possible. As we shall see, in large part it was this boundary between two environments and between two economies which marked the northern limit of Mesoamerica -- the region of high native cultures on the North American continent.

               The shift to an agricultural economy in those geographic areas of the Americas where such a transition was possible was also accompanied by a change in the spatial patterns of behavior of the peoples involved. Whereas a hunting-and-gathering society was almost of necessity a nomadic one, with its members following the migrations of game or the seasonal variations in the fruiting of plants, a farming society -- at least one based on such higher-order plants as maize, beans, and squash -- tended to become more geographically fixed. The investment of time and labor in clearing land, planting seeds, weeding, watering, and fertilizing, and ultimately harvesting the mature crop meant that agricultural peoples became more settled in place. Moreover, because farming entailed an active "partnership" in the production of food, rather than just a passive collection of whatever bounty nature provided locally, the food supply usually became not only more secure and dependable but also capable of supporting larger numbers of people. Population densities began to increase and, depending on the land-use patterns which developed, more and more people tended to live together in small villagelike settlements. This inevitably resulted in greater social interaction, with all the positive and negative consequences that such contact brings in its wake.

               Where agriculture was practiced under especially favorable conditions -- and usually such geographic areas were discovered by accident rather than by conscious design -- it was even possible to produce more food than the local inhabitants actually needed at any given time. The significance of being able to produce surplus food can scarcely be overemphasized, for by releasing some workers from the day-to-day chores of tilling the fields, it permitted a diversification and specialization of labor that had never before been possible. In the Old World, such specially favored areas of food production had been found in the so-called exotic river valleys of the Near East, such as the Tigris and Euphrates, as early as 4500 B.C.; in the Nile Valley of Egypt by 4000 B.C.; the Indus Valley of Pakistan by 3500 B.C.; the valleys of the Amu and Syr Darya in Central Asia by 3000 B.C.; and the Wei river valley of North China by 2500 B.C. In every instance a desert climate with cloudless skies, 12 hours of daily sunshine, the absence of frost, little or no vegetation cover to clear, and rich alluvial soils coincided with a continuous supply of water from the adjacent river -- true "Gardens of Eden" in which only the totally lazy and indifferent could have failed to enjoy the blessings of plenty. Indeed, each of these exotic river valleys was either the cradle of a civilization in its own right or, at least, the beneficiary of a diffusion which first began in Mesopotamia and was later emulated elsewhere under remarkably similar environmental conditions.

               It should also be pointed out that in the wake of surplus food production and the concomitant necessity for food storage, a couple of modifications in the material culture of the peoples concerned were almost inevitable hallmarks of such an advance. Vessels for storage, such as baskets and pottery, now became part of the inventory of the average household. And the latter, in particular because of its relative imperishability, has become a favored diagnostic tool of the archaeologist in tracing the economic evolution of a culture. Although examples of pre-agricultural ceramics do exist, the more usual case is that they are evidence of a settled, farming society of greater complexity and sophistication. We shall return to the role of ceramics somewhat later.

               There is good evidence that in the New World the model of "hydraulic" civilizations described above was first replicated in the Atacama Desert of Peru where about 40 short exotic rivers cut their way from the Andes to the Pacific. However, in the region which we have called Mesoamerica, no such exotic river valley environment exists, though a somewhat similar lacustrine setting eventually gave rise to the regions largest metropolis, Teotihuacán, and later to its most sizable heir, the Aztec capital of Tenochtitlán. Nevertheless, in the latter region, archaeologists have been unable to pinpoint any single, well-defined cradle for the rise of civilization in the same way as they have in most of the other great cultural hearths of the world. While most archaeologists are now agreed that the oldest, or "mother," culture of the entire region is that of the misnamed Olmecs, who these people really were and where they came from are still matters of some dispute.

               As originally defined, Mesoamerica was a region whose boundaries embraced the geographic core area of the pre-Columbian civilizations of the North American continent. As such, it was a cultural concept whose unifying characteristics were the very hallmarks of the more advanced indigenous societies, among them a hierarchical political structure, an urban way of life, monumental architecture, a highly developed religious pantheon, a sophisticated calendrical system coupled with a knowledge of astronomy and mathematics, and the use of a hieroglyphic form of writing. But, because it was primarily a region defined by human achievement, its boundaries have tended to fluctuate through time; thus, the frontiers of Mesoamerica in the distant past were quite different than they were on the eve of the Spanish conquest. Indeed, the region as it is generally defined today represents the culmination of a long, slow process of geographic diffusion throughout southern Mexico and northern Central America.

               Although Mesoamerica was essentially a cultural concept, its dimensions had a very real physical basis. It was a region in which maize not only could be grown but within which it also became the staple foodstuff of civilization itself. Everywhere the warmth and moisture were adequate, though the latter was only seasonally so because of the monsoonal nature of the climate. Over most of Mesoamerica, the rains were associated with the summer, or high-sun, half of the year, whereas during the winter, or low-sun, period, the amount of precipitation received fell considerably short of what most plants, wild or domesticated, required for active growth. As a result, much of the vegetation demonstrates an adaptation to drought, whether in size of plant, density of plant cover, loss of leaves, or modification of leaf structure to retain moisture. Where the total annual precipitation is especially heavy and/or the seasonal drought is relatively brief, the resultant vegetation is a tall and luxuriant rain forest, or selva. Elsewhere it grades into a lower deciduous forest and in northernmost Yucatán into a scrub forest of relatively short thorn trees. Some interior upland valleys border on being steppe.

               The productivity of the soil varies both with the nature of the bedrock from which it has been derived and with the wetness of the climate. Without question, the region's most productive soils are the alluviums laid down along the major rivers, especially of the Mexican Gulf coastal plain, but the limestones which underlie the Yucatán and much of southern and eastern Mexico and the northern highlands of Guatemala also contribute to the fertility of these areas, even where the rainfall is relatively heavy. On the other hand, because limestone is porous, most such areas have no surface streams, all the rainwater having drained down into the water table which often lies at a depth of many feet. As a result, water is in short supply and where there is a paucity of rainfall to begin with, as in the northern Yucatán, much of the original limestone surface is so little weathered that the farmer's fields are almost nothing but bare rock. However, in addition to the areas with alluvial soils and lime-rich soils, areas of recent volcanic activity such as central Mexico and the southern highlands of Guatemala contain mineral-rich soils which have supported a dense settlement of sedentary agriculturalists for literally hundreds of years. On the other hand, in some of the mountainous areas of western Mexico where the bedrock is composed largely of igneous intrusive rocks such as granite or metamorphic rocks, such as gneiss and schist, the resultant soils tend to be sandy, porous, and relatively sterile, and crop yields tend to be low and farming populations consequently small.

               Thus, the challenges posed to the would-be farmer in Mesoamerica varied markedly from place to place, with soil fertility and adequacy of moisture being the most critical factors determining the success of agriculture in the region. And while no people or society set out consciously to find the "magic" combination of geographic factors which would allow them to produce a surplus of food which would then in turn set the wheels of civilization in motion, in at least one place within the region a fortuitous natural endowment had favored such a development even before farming had become a viable option. This was in Soconusco -- that part of Mesoamerica which lies in the Pacific piedmont of Guatemala and the adjacent area of southernmost Mexico.


               Perhaps few other regions of the Americas demonstrate as great a physical and ecological diversity within such a limited area as does Soconusco.  If we are generous in its dimensions, we can say that it extends for roughly 300 km. (200 mi) northwest-southeast along the Pacific versant of Mexico and Guatemala, beginning around the present-day town of Tonalá and extending to just south of Guatemala City. Because its inland boundary coincides with the continental divide, its overall width is nowhere more than about 50 km (30 mi). Thus, its total area is less than 15,000 sq km (6000 sq mi), or smaller than the size of the states of Connecticut and Rhode Island taken together.


Figure 1. Topography is shown by increasing intensities of shading, with areas from sea level to 200 in (650 ft) in the lightest tone, areas from 200 to 1000 m in the next darkest tone, areas between 1000 and 3000 in darker yet, and areas above 3000 m (10,000 ft) in the darkest tone. The height and ruggedness of the mountain wall backing Soconusco insured the region a measure of isolation and protection from the interior in the earliest stages of its cultural evolution and have continued to complicate inland communications to the present day.


               Within this small area the topography varies from sea level to over 4000 m (13,000 ft) in elevation. Indeed, the highest mountains in all of Central America are found in Soconusco -- Tajumulco (4221 m, 13,845 ft) lying in Guatemala about 30 km (20 mi) from the Mexican frontier, and Tacaná (4094 m, 13,428 ft) itself forming part of the boundary. Yet, even the mountains themselves contribute to Soconusco's diversity, for from Tacaná south they are all of volcanic origin whereas on the Mexican side of the line they are chiefly composed of granite. Consequently, the resultant soils differ as well, those in Guatemala being relatively fertile while those in Mexico are primarily sterile sands. However, two factors combine to mitigate the essential poverty of the soils in the Mexican coastal plain. First, the deposits of volcanic lava, ash, and dust have weathered more rapidly and more deeply than have the granites, with the result that a vaster amount of alluvial material has been brought down in the Guatemalan sector of Soconusco than in the Mexican. Consequently, the Guatemalan coastal plain is wider than that in Mexico. Second, because the predominant long-shore current in the Pacific is from the south, the alluvium derived from the volcanic debris has been swept northward along the Mexican coast so that most of the outer lagoon areas have become the recipients of finer, more productive soils than those found farther inland near the granite foothills.

               Because of its latitude (i.e., 13-17º N), Soconusco has a distinctly tropical climate with a very small temperature range throughout the year. The coldest month averages 27º C (80º F) while the mean for the warmest month does not climb above 30º C (86º F). Warmth, therefore, is both constant and essentially unvarying in Soconusco, unlike parts of eastern Mexico where the occasional passage of nortes (northers) from December to February can brusquely drop temperatures into the lower teens C (50's F).

               On the other hand, in common with all of Mesoamerica, Soconusco experiences a decidedly monsoonal pattern of rainfall. Whereas the constantly high temperatures mean that on average 130-160 mm (about 5 - 6 in.) of moisture could be theoretically transpired and/or evaporated into the atmosphere every month, in at least five months of the year the average precipitation fails to reach that amount. Thus, from December through April there is a steadily growing moisture deficit within the region, totaling a shortfall of over 550 mm (about 22 in.) by the time the summer rains begin. However, once the rains commence, they are so heavy that the total dry-season deficit is more than made up by the end of June, and thereafter the surplus continues to grow. The maximum monthly rainfall occurs usually in September when the onshore flow of moisture is reinforced by the occasional passage of a tropical storm or hurricane along the coast; in that one month alone the surplus normally totals more than 500 mm (20 in.). Although the rainfall tapers off rapidly in November as the winds begin to reverse their direction and blow off-land from the American Southwest, by the end of the rainy season the surplus of moisture has grown to more than 2200 mm (86 in.). Even after the deficit from the dry season is subtracted from this amount, it will be seen that Soconusco receives a surplus of over 1650 mm (65 in.) of rainfall each year, ensuring that the streams of the region run all year and that the vegetation over most of the area retains its character as a lush rain forest.

               Naturally, the greatest climatic variations within Soconusco result from differences in elevation. Distinctly tropical species of trees, plants, and crops are found up to a height of just over 900 m (2950 ft), whereas typical subtropical plants climb to something over 1900 m (6200 ft). Warm-temperate types of vegetation, including maize, for example, find their ecological niche up to 2600 m (8500 ft), and cool-temperate species thrive up to 3000 m (9800 ft). Above that elevation, the predominant vegetation is composed of coniferous trees such as numerous types of pine and the fir. For all intents and purposes, the tree line is found at about 3250 m (10,700 ft), which means that the remaining 1000 m (3300 ft) before the crest is reached is characterized by a tundra, or páramo, type vegetation. (To be sure, all of these limits rise somewhat the farther one moves toward the equator.) Of course, through this entire climb not only does the precipitation increase with elevation but so does its effectiveness, because both the transpiration and evaporation rates decrease. Thus, the higher slopes of the mountains of Soconusco experience a super-humid climate; that is, the precipitation which they receive totals well over twice the amount which the plants or crops in the region require for their growth.

               Reflecting this broad spectrum of habitats -- ranging from brackish mangrove-laced lagoons at sea level to cloud forests and páramos on the mountain crests -- is a richly diversified fauna of marine life, animals, and birds. With fish, shrimp, lobster, mussels, turtles, and aquatic birds inhabiting the coastal lagoons and deer, tapir, and peccary roaming the foothills, the earliest hunters-gatherers-fishers-and-fowlers who happened into Soconusco encountered such a richly diversified and bountiful food supply that it is likely that little more than 10 to 15 man-days per month were required to feed themselves.


Figure 2. A water budget diagram for Tapachula, the main city of Mexican Soconusco today. Two curves are seen in the diagram -- one relatively even line running across the graph which depicts water need and a second, very uneven line running off the top of the graph which shows monthly precipitation. Water need is a direct function of temperature, and in every month of the year the warmth is such that about 125 mm (5 in.) of precipitation is required to meet the needs of growing plants. From November until April -- the low-sun, or winter, months -- the actual precipitation falls below this threshold, resulting in a deficit of moisture (the areas shown in yellow). However, the rains begin with a vengeance in late April and far exceed the water need of the region until early November. This seasonal shift from low-sun drought to high-sun surplus (the area in blue) is typical of what the geographer calls a "monsoonal" climate. The fact that the accumulated warmth -- i.e., the warmth index --  totals more than 8.0 means that Soconusco is decidedly tropical, whereas the fact that the moisture index is well above 1.0 means that it is a humid climate that supports the growth of dense forest vegetation. (Data from Secretaría de Recursos Hidráulicos.)


               Certainly, the needs for clothing and shelter were minimal. Indeed, the manner in which the local inhabitants saw fit to cover their nakedness was dictated more by modesty than by necessity. Protection from the elements involved little more than providing a place where the heavy rains and the broiling sun could be excluded, where foodstuffs could be stored, and where some measure of privacy could be obtained. If unwelcome insects and wild animals could be shut out as well, so much the better. For this purpose, the pole hut, or palapa, with its steeply pitched roof of palm fronds and relatively open-weave walls for ventilation was as basic and practical a solution as could be imagined.

               To secure one's livelihood it was necessary to fashion both tools and weapons, and for these the fundamental raw materials were stone, bone, and wood. Although the granite ridges of southern Mexico afforded little workable stone for tool making, in the volcanic deposits of Guatemala were local outcrops of obsidian, which was highly prized for the razor sharp edges it lent to arrowheads, spear points, and knife blades (Clark and Lee, 1984, 225). As people pushed their quest for sustenance into the water realm, at first they waded into the shallow lagoons on their own, and later ventured into deeper water buoyed by logs lashed together with vines and with casting-nets fashioned from the fibers of reeds or lianas. Still later they began making canoes by hollowing out large logs using either axes or fire or both. Thus, both on land as hunters and gatherers and in the coastal marshes and lagoons as fishers and fowlers, the residents of Soconusco were quick to develop a tool kit which allowed them to successfully exploit the rich variety of resources which they encountered. Thus, during even the earliest cultural horizon which the archaeologists working in this area have recognized -- the so-called Chantuto period (4650-1850 B.C.) -- it seems that the inhabitants of Soconusco enjoyed not only a freedom from want (i.e., a surplus of food) but also a considerable measure of leisure time. (See Table 1 for the chronology of the Soconusco region as it has been developed by archaeologists of the New World Archaeological Foundation. In Table 2 a more generalized chronology applicable to the entire Mesoamerican region is presented.)


Table 1 - Archaeological Chronology of Soconusco

Name of Phase



Chantuto A

4650 - 3400 B.C.

Hunters, gatherers

Chantuto B

3400 - 2150 B.C.

Fishers, fowlers


2150 - 1850 B.C.


1850 - 1650 B.C.


1650 - 1500 B.C.



1500 - 1350 B.C.



1350 - 1200 B.C.

Olmec influence


1200 - 1000 B.C.



1000 - 950 B.C.


Early Conchas

950 - 850 B.C.

Late Conchas

850 - 750 B.C.

Source: "The Beginnings of Mesoamerica: Apologia for the Soconusco Early Formative," John E. Clark (director, New World Archaeological Foundation), p. 15.

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _    


Table 2 - Generalized Mesoamerican Chronology



Major Sites



1200 - 1000 B.C.

San Lorenzo


1000 - 300 B.C.

La Venta, Monte Albán


300 B.C. - A.D. 300




A.D. 300 - 600

Tikal, Copán


A.D. 600 - 900

El Tajín, Uxmal



A.D. 900 - 1200

Tula, Mitla


A.D. 1200 - 1500


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