The early evidence for human occupation

As elsewhere, there are formidable holes in the archeological records relating to initial human entrance into the now-humid Neotropics, and new evidence tends to accumulate slowly because early human groups were small and often highly mobile, leaving behind few tangible remains. Nonetheless, we know considerably more about the subject now than we did 10 to 15 years ago. There is convincing evidence of human occupation dating to the Late and terminal Pleistocene periods—between c. 15.2 kcal. yr bp and 11.8 kcal. yr bp (13k14Cyr bp and 10k 14CyrBP)—from a number of localities (Figure 7.1). The best-studied regions are often those of seasonally dry areas of southern Central America and northern South America, where focused archeological research has been of longer duration and broader scale (e.g., Cooke, 1998; Lopez Castano, 1995; Mora and Gnecco, 2003; Ranere and Cooke, 2003;

Stothert et al., 2003). A related and significant factor is that forests in many of these areas have unfortunately long been cleared, making it much easier for archeologists to find and excavate ancient human occupations.

In much of tropical lowland Mesoamerica, including Mexico (but see Pope et al., 2001), research has been more spotty, owing to the relative ease of finding sites in the sparsely vegetated areas of the region's arid and semi-arid zones. The dry highlands of Mexico, which have seen seminal work (MacNeish, 1967; Flannery, 1986), have traditionally been more politically stable as well. Research in potentially important seasonally dry tropical areas in the states of Guerrero, Michoacan, and Chiapas (Mexico) directed toward documenting Late Pleistocene and Early through Middle Holocene human adaptations is just beginning (Voorhies et al., 2002; Piperno et al., 2004). Similarly, in the seasonal forests of Bolivia and southwestern Brazil, where it appears that famous staple crops—such as manioc (Manihot esculenta Crantz) (Olsen and Schaal, 1999)—were domesticated, archeological research is presently underdeveloped and very little information is available on early human settlement and economic systems.

Significant information has been generated over the last 15 years concerning earliest human presence in the Amazon Basin, which at the site of Caverna de Pedra Pintada, located near Santarem just 10 km north of the main Amazon river channel, is convincingly dated to c. 12.9 kcal. yr bp (Roosevelt et al., 1996). Human settlements were present in the wet forests of the western Amazon Basin (middle Caqueta river area of Colombia) before c. 10.1 kcal. yr bp (Cavelier et al., 1995; Mora and Gnecco, 2003). However, the Amazon Basin is so vast (about the size of continental U.S.A.) and often well-forested that it will be many years before any consensus is reached concerning the timing, passage routes, and possible ecological foci of early human settlement. These questions are particularly important with regard to the cultural and environmental history of the terra firme forests (those not under the influence of watercourses), which occupy 98% of the land area of Amazonia, and contain some of the poorest soils and lowest concentrations of plant and animal resources found anywhere in the tropics (Piperno and Pearsall, 1998). There has been a long-term and vocal dichotomy of views over whether the terra firme forests were well-occupied and farmed in prehistory, which only will be resolved with much more archeological research (see Neves, 1999 for an excellent review of these and other issues in Amazonian archeology).

Figure 7.1 is a map showing the Late and terminal Pleistocene archeological sites that have been located and studied. Also extremely relevant to the issue of early human settlement in the tropics is that a long and classic debate has just been concluded concerning the initial peopling of North and South America as a whole. Tom Dillehay's excavations at the site of Monte Verde, located in a wet temperate forest in southern Chile (Dillehay, 1997), overturned the "Clovis First'' paradigm that had previously dominated archeology, especially in North America, and that held that humans were present in North America no earlier than c.11,200 bp (Meltzer, 1997). The oldest radiocarbon dates at Monte Verde go back to nearly 13,000 bp. The site is now accepted as convincing proof for an early human presence in South America by a strong consensus of archeologists. Other archeological sites located to the north of

Monteverde Archaeological Site Map

Figure 7.1. Locations of archeological sites in the Neotropics (opposite page) that date to between c. 15.4 kcal. yr bp and 11.4 kcal. yr bp placed against a reconstruction of Central and South American Pleistocene vegetation (above). Modified from Piperno and Pearsall (1998, figs. 4.1a and b). PC = Pre-Clovis site. P/P = Pre-Clovis and Paleoindian site. P = Paleoindian site. More detailed information on the sites can be found in Dillehay et al. (1992), Lopez Castano (1995), Roosevelt et al. (1996), Cooke (1998), Piperno and Pearsall (1998), and Ranere and Cooke (2003). Black areas are mountain zones of 1,500 m a.s.l. and greater. Grey area along coastlines is land exposed by sea level drop; in most cases, exposed land probably contains vegetation similar to adjacent terrestrial zones. The vegetation reconstruction is based on available paleoecological sequences and, for regions where such information is not available, reasonable extrapolations of data. The reconstruction is intended to provide broad guides to glacial-age vegetation. For more information on the archeological sites see Piperno and Pearsall, 1998, pp. 168-175. Explanation for the vegetational reconstruction in the figure:

20"

Figure 7.1. Locations of archeological sites in the Neotropics (opposite page) that date to between c. 15.4 kcal. yr bp and 11.4 kcal. yr bp placed against a reconstruction of Central and South American Pleistocene vegetation (above). Modified from Piperno and Pearsall (1998, figs. 4.1a and b). PC = Pre-Clovis site. P/P = Pre-Clovis and Paleoindian site. P = Paleoindian site. More detailed information on the sites can be found in Dillehay et al. (1992), Lopez Castano (1995), Roosevelt et al. (1996), Cooke (1998), Piperno and Pearsall (1998), and Ranere and Cooke (2003). Black areas are mountain zones of 1,500 m a.s.l. and greater. Grey area along coastlines is land exposed by sea level drop; in most cases, exposed land probably contains vegetation similar to adjacent terrestrial zones. The vegetation reconstruction is based on available paleoecological sequences and, for regions where such information is not available, reasonable extrapolations of data. The reconstruction is intended to provide broad guides to glacial-age vegetation. For more information on the archeological sites see Piperno and Pearsall, 1998, pp. 168-175. Explanation for the vegetational reconstruction in the figure:

1. Largely unbroken moist forest, often with a mixture of presently high-elevation and lowland forest elements. In some areas, montane forest elements (e.g., Podocarpus, Quercus, Alnus, Ilex) are conspicuous. Annual precipitation is lower than today, but sufficient precipitation exists to support a forest.

2. Forest containing drier elements than characteristic today. High-elevation forest elements occur, especially in moister areas of the zone. Areas near the 2,000-mm precipitation isohyet and areas with sandy soils may contain savanna woodland. The vegetation may be patchy.

3. Mostly undifferentiated thorn woodland, low scrub, and wooded savanna vegetation. Some regions (e.g., Guatemala) have temperate elements (e.g., Juniperus). Areas receiving greater than 2,000mm of rainfall today may still support a drier forest, as in 2. River- and stream-side locations support a forest.

4. Quite possibly, a drier vegetation formation than 5 (below), with fewer trees and more open-land taxa. Paleoecological data are lacking for the zone.

5. Fairly open and humid forest containing many presently high-elevation taxa (e.g., Ilex, Podocarpus, Rapanea, Symplocos) combined with elements of the modern semi-evergreen forest and cerrado. Precipitation is lower than today but northward shifts in the southern polar fronts and other factors ameliorate precipitation reduction. The modern, seasonal forest-cerrado vegetational formations of the region are not present until about 10,000 bp

6. Desert/cactus scrub.

Caverna Pedra Pintada

El Cayude (P) - Taima-Taima

Caverna de Pedra Pintada (P)

El Cayude (P) - Taima-Taima

Caverna de Pedra Pintada (P)

Map Caverna Pedra Pintada

Minas Gérais State Sites

Alice Boer

Minas Gérais State Sites

Alice Boer

Monte Verde—such as El Abra and Tibitó, Colombia, and Taima-Taima, Venezuela, that were controversial before Monte Verde was excavated—also contain convincing proof of human occupation at c. 15.4-13.8 kcal. yr bp (Figure 7.1) (Dillehay et al., 1992; Cooke, 1998; Ranere and Cooke, 2003). Therefore, human populations must have first moved through Central America at an earlier time, although no incontrovertible sites dating to before c. 12.9 kcal. yr bp have been found yet (Cooke, 1998; Ranere and Cooke, 2003).

Claims for a pre-13,000 bp human presence in South America, including a cave in northern Brazil known as Pedra Furada, are not well-supported because artifacts were not recovered from securely dated contexts, or pieces of stone attributed to human manufacture do not display convincing signs that they had been altered and used by people (e.g., Meltzer et al., 1994; Piperno and Pearsall, 1998, p. 169). Thus, there is no convincing evidence at the present time that people occupied the Neotropics during the Last Glacial Maximum and the 3,000 or so years immediately following it.

7.3.2 Pleistocene landscapes and early human modification of them

Of course, showing that people were living at tropical latitudes during the Pleistocene is not the same as proving they were living in tropical forest and surviving off its resources. In fact, early scholars assumed that the earliest hunters and gatherers of the New World preferentially exploited the numerous, now-extinct large game animals that were available to them. These investigators proposed that, because megafauna and other sizeable animals would have been rare in tropical forest, humans migrating from north to south would have largely avoided densely wooded areas, living instead in the more open landscapes they believed characterized the Pacific watershed of Central America, northern South America, and the intermontane valleys of the Andes (e.g., Sauer, 1944; Lothrop, 1961; see Ranere, 1980 for one of the first robust counterarguments based on archeological excavation and analysis). Some scholars writing later would agree with this assessment, going so far as to argue that Holocene hunters and gatherers could not have survived for long in tropical forest without access to a cultivated food supply because wild food resources, especially carbohydrates, were supposedly scarce (e.g., Bailey et al., 1989; see Colinvaux and Bush, 1991 and Piperno and Pearsall, 1998 for responses and further discussion).

The large corpus of paleoecological data accumulated during the past 20 years, discussed in detail in other chapters of this book, shows that Late Pleistocene environmental conditions were indeed significantly different from those of the Holocene in ways that could have influenced early human colonization and the specific kinds of habitats that early hunters and gatherers exploited. Reconstructions from lacustrine pollen and phytolith data demonstrate the presence of a variety of vegetation communities. These range from dense, species-diverse forest to open, shrub- and grassdominated formations. There is strong evidence indicating some regions were considerably drier than today during the Late Pleistocene—for example, Peten, Guatemala, much of Pacific-side Central America, and parts of northern South America. At the present time, these regions receive between 1.2 and 2.6 meters of precipitation and their potential vegetation is deciduous or drier forms of semi-evergreen forest. During the Late Pleistocene, their vegetational formations were dominated by low woodlands, thorn scrublands, and savannas (Leyden, 1984, 1985; Leyden et al., 1993; Piperno and Pearsall, 1998; Piperno and Jones, 2003). It was during the first 2,000 years of the Holocene that tropical forest developed on these landscapes. Recently accumulated data from lakes and large swamps located in the Rio Balsas watershed in tropical southwest Mexico (Guerrero state), where the potential vegetation is a tropical deciduous forest, indicates a drier Late Pleistocene climate and more open vegetation there as well (Piperno et al., 2004). Thus, when humans first penetrated tropical latitudes, forests did not cover landscapes to the extent they do today.

Where, however, annual rainfall is above about 2.6 meters today and the actual or potential vegetation is evergreen and semi-evergreen forest, the evidence is strong that Pleistocene landscapes were mostly forested. This is empirically demonstrated in Caribbean-side Panama at the Gatun Basin (Bartlett and Barghoorn, 1973), and probably was the case throughout most of the Caribbean watershed of Panama, Costa Rica, Nicaragua, and Honduras. It is also demonstrated at Pacific watershed sites in Panama at elevations of between 500 and 700 m above sea level, such as La Yeguada and El Valle (Bush et al., 1992; Bush and Colinvaux 1990), and at various locations in South America (see Colinvaux et al., 1996a, b and Chapter 3 in this book). Therefore, considerable portions of the Pleistocene Neotropical landscape were forested.

How can we relate this corpus of data on environmental history to questions concerning early cultural adaptations to tropical latitudes? Arguably, one of the best ways is to correlate reconstructed Pleistocene vegetation with archeological sites of the same age located nearby. If, for example, human settlement before c. 11.4 kcal. yr bp is largely confined to open areas, the implication would be strong that forests were not persistently lived in and that human populations were surviving for the most part off resources typical of non-wooded environments (e.g., large animal game and plants like cacti and tree legumes found in drier types of vegetation). Another way to assess the issue is to examine actual dietary evidence from archeological sites to directly determine what kinds of resources people were exploiting. There is presently more evidence to consider from the first than from the second option. Fortunately, some of the best-documented archeological sites are located near lakes from which detailed paleoenvironmental information has been generated. Furthermore, in the cases where early archeological sites are not in the vicinity of old lakes, major characteristics of the Pleistocene environment can still be reasonably inferred for them by using paleoe-cological information recovered from zones with a similar modern potential vegetation. When the relevant data are evaluated, the following patterns emerge (see Piperno and Pearsall, 1998, pp. 169-175, for more details) (Figure 7.1).

The few available archeological sites where a pre-Clovis (pre-12.9kcal. yr bp) occupation is indicated are located in deserts/grasslands/open woodlands at low elevations in northern South America (two sites in Venezuela) and open environments (paramo) at two northern Andean locations. No incontrovertible human occupation is located so far in an area reconstructed as having supported tropical forest vegetation. However, the number of sites is still far too few to draw firm conclusions as to whether people of this time period were preferentially selecting one type of habitat and its plant and animal resources over another.

Archeological sites of later, Paleoindian age—c. 12.9-11.4 kcal. yr bp (11-10k 14CyrBP)—are greater in number and more likely to be representative of habitat choices that people made, and the sites were located in a diverse array of environments. (For purposes of simplicity, I call all human occupations dated to between c. 12.9 kcal.yr bp and 11.4kcal. yr bp Paleoindian, even though all of them do not contain characteristic Clovis culture types of tools.) They included alpine meadow (in Guatemala), low- and higher-elevation forest (e.g., in Panama, Costa Rica, Colombia, and Brazil), and open, thorny, and/or temperate scrub/savanna types of vegetation (e.g., in Mexico, Belize, Panama, and Venezuela) (see Cooke, 1998; Piperno and Pearsall, 1998, pp. 169-175; and Ranere and Cooke, 2003 for further descriptions of these sites).

Out of the 24 Paleoindian localities included in this survey, 10 were located in some kind of tropical forest. Moreover, moving through southern Central America and entering South America without encountering and living in forest some of the time may not have been possible. Data on human dietary patterns recovered from the sites that can buttress arguments of tropical forest occupation and resource exploitation are often scant because people typically did not stay in one spot long enough for a sizeable midden of food and other remains to accumulate. However, Caverna de Pedra Pintada in Brazil yielded abundant carbonized nut and seed fragments from a variety of trees—such as palms and Brazil nuts—as well as faunal remains of large and small mammals that were clearly derived from the forest and were dietary items (Roosevelt et al., 1996). The archeological phytolith and carbonized seed and nut record from central Panama also contains indications that tropical forest plants were being exploited and eaten between c. 12.9 kcal. yr bp and 11.4 kcal. yr bp (Piperno and Pearsall, 1998; Dickau, 2005).

We should remember that Pleistocene forests were often considerably different in their floristic compositions when compared with forests that grow in the same areas today; few of them appear to have modern analogs. Thus, we cannot expect to be able to directly compare potential plant and animal resources of modern forests with those that existed during the Late and terminal Pleistocene periods. In many areas, forests probably contained more trees tolerant of lower rainfall than extant examples, and they perhaps had more open canopies due to reduced precipitation and also lowered light use efficiencies during photosynthesis that resulted from reduced atmospheric CO2 concentrations (Sage, 1995; Cowling and Sykes, 1999). Phytolith studies of the Gatun Basin core sequence from Panama, which is located very near the Madden Lake Paleoindian archeological sites, add some empirical weight to these inferences (Piperno et al., 1992). They indicate that prior to c. 11.4 kcal. yr bp arboreal associations contained more trees characteristic of modern deciduous forests—such as the Chrysobalanaceae. Pre-11.4kcal. yr bp phytolith records are, in fact, a very good match with those constructed from directly underneath modern deciduous forest in Guanacaste, Costa Rica. In contrast, plants that are significant components of modern semi-evergreen forests of the area (e.g., the Annonaceae [Guatteria], bamboos [Chusquea], and palms) don't enter the Gatun Basin record until after 11.4 kcal. yr bp (Piperno et al., 1992).

Thus, these records appear to reveal a significant change in forest composition over the Pleistocene/Holocene boundary characterized by increases of trees and understorey plants that were likely responses to rising moisture levels. In Panama and probably elsewhere, the Pleistocene forests that humans occupied were likely to have been drier and more open—and possibly contained a higher animal biomass— than those that grow in the same regions today.

We should also remember that early human populations appear to have been actively modifying on their own the new landscapes they were encountering—largely, it seems, by fire. For example, at Lake La Yeguada, Panama, where detailed, multiproxy assessments of fire and other vegetational disturbances were carried out by the author, Mark Bush, and Paul Colinvaux, frequencies of charcoal and burnt phytoliths indicate that human firing of the vegetation around the 16,000-year-old lake began at c. 12.9 kcal. yr bp and continued without pause through the Early and Middle Holocene periods (Piperno et al., 1990, 1991a, b). Archeological data document initial human colonization of the lake's watershed when vegetational disturbances are first apparent. In fact, a projectile point that dates to some time in the 12.911.4 kcal. yr bp period was found on the La Yeguada shoreline (Ranere and Cooke, 2003). The lacustrine evidence, which includes detailed comparisons of the phytolith, pollen, and charcoal information with modern analog data from different types of mature forests and culturally modified vegetation, has been discussed in detail and illustrated elsewhere and will not be repeated here (e.g., Piperno 1993, in press c; Piperno et al., 1990, 1991a, b; Bush et al., 1992). A summary of some of the data is provided in Figure 7.2, where it can be seen that records of burnt phytoliths at La Yeguada show close resemblances to phytolith profiles constructed from modern vegetation undergoing active human disturbance, but not from modern forests experiencing little to no human activity.

7.3.3 After the Pleistocene: the origins and spread of tropical forest agriculture during the Early Holocene

As in several other areas of the world, the lowland Neotropical forest witnessed an independent emergence of plant food production and domestication not long after the Pleistocene ended (Piperno and Pearsall, 1998; Diamond, 2002). Combined information from archeological, molecular, and ecological research tells us that—out of the more than 100 species of plants that were taken under cultivation and domesticated by native Americans before Europeans arrived—more than half probably came from the lowland tropical forest (Piperno and Pearsall, 1998; Piperno, in press a). Both hemispheres of tropical America were involved. In lower Central and northwestern South America, where the greatest amount of work has been carried out to date, the domestication and spread of important native crops like maize (Zea mays), manioc (Manihot esculenta), at least two species of squash (Cucurbita moschata and C. ecuadorensis), arrowroot (Maranta arundinacea), yams (Dioscorea trifida), and liren (Calathea allouia) between 10,000 and 5,000 years ago has been empirically documented through phytolith, pollen, and starch grain research (Pearsall, 1978; Monsalve, 1985; Mora et al., 1991; Piperno and Pearsall, 1998; Bray, 2000;

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Responses

  • Rita
    What kind of human occupation is in mexico?
    8 years ago
  • BONNIE
    Are there any archeological sites in the tropical rainforest?
    3 months ago

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