There has been a great deal of discussion in professional and public outlets recently about the scale and intensity of indigenous alteration of tropical landscapes before European arrival, especially in Amazonia. Arguments concerning prehistoric landscapes are increasingly being polarized into ‘pristine’ versus ‘cultural parkland’ scenarios and soon it will be politically incorrect to argue that Native Americans did not profoundly alter their landscapes and even reduce biodiversity in some places (20 years ago the opposite was the case). However, palaeoecological data indicate that the chronologies, severity, and trajectories of human impacts varied considerably.
It makes sense that seasonal tropical forests, where soils are most fertile and many staple seed and root crops appear to have been originally domesticated, were probably more significantly affected over more protracted timescales than were forests in nonseasonal regions, where soils were poorer, vegetation did not hold as many nutrients and was much harder to burn effectively, and crop plant evolution largely did not take place. Regions that otherwise supported early agricultural developments through participating in the initial dispersals of domesticated plants, as occurred in Central Pacific Panama, for example, also were likely to have experienced early and significant forest modification. Many anthropologists and archaeologists still do not understand the importance these contrasting ecologies - seasonal versus aseasonal - had for prehistoric cultural developments in the tropical forest. Even today, population densities in the lowland tropics are higher and agriculture is more developed and sustained in areas of former drier forest. The result is that far fewer of these forests remain than semi-evergreen and evergreen formations, contributing to the greater distinction that rain forests enjoy.
The geographer Carl Sauer was one of the most erudite scholars who studied early humans in the tropical forest, and his comment that ‘‘the mastery of the forest requires no axe’’ has been shown by palaeoecological data to be particularly prescient. Everywhere a record of agriculture is recorded by way of cultivar presence and forest clearance, charcoal frequencies are also very high. As Sauer also noted, Neotropical trees are thin-barked and therefore poorly insulated and can be easily killed by simple ringing and fire, making the use of stone axes irrelevant during early periods of food production in areas having long and marked dry seasons. In central Panama, for example, stone axes did not become common until shortly after 3000 BP, when a major settlement shift occurred and people had to clear the larger trees and moister environments of the major river valleys for the first time.
The recent discovery in the Amazon of large areas of terra preta, black earth containing ceramics and organic cultural debris and probably representing middens formed by dense and permanent human settlements, at numerous places near water courses, together with the excavations of what were large and permanently occupied sites in regions such as the upper Xingu that are replete with defensive structures and linked by extensive roadways, make it abundantly clear that starting at about 2000 BP, parts of the Amazon Basin near major rivers and tributaries were indeed very well populated in later prehistory. We should take care, however, not to extend these findings to other areas of the Amazon, especially the interfluves (areas located away from major watercourses and tributaries also called the terra firme forests, where soils and overall resource abundance are much poorer), until a lot more data are in hand. We know next to nothing about prehistoric society in the enormous expanses of the interfluves, but already detailed palaeoecological information from large lakes located just 15 to 30 km north of the main Amazon river channel near Santarem indicates that human landscape alteration occurred later and was not as severe as what transpired in extra-Amazonian contexts in South and Central America, and probably along waterways of Amazonian areas just described where large settlements have been documented.
Moreover, there still is no evidence for maize or manioc agriculture anywhere in core and eastern Amazonia until after 4000 BP (David Browman and colleagues inaccurately imply that the crops have been documented with phytolith and pollen evidence earlier than that). Similarly, when the author studied phytolith-rich records from terrestrial soils sampled from directly underneath a forest preserve 90 km north of Manaus, Brazil, she could not detect a human influence on the vegetation during the past 7000 years. Future archaeological research should reveal whether areas like these for some reason never supported persistent human occupation. In short, facts on the ground are at variance with the pristine forest vs. cultural parkland dichotomy in the Amazon and elsewhere.
The Amazon Basin is precious for natural and social scientists of all stripes because it holds the greatest contiguous expanse of tropical forest and largest store of biodiversity in the Americas, together with a lot of the remaining indigenous cultural and linguistic diversity. Other, long-neglected regions of tropical Central and South America are demonstrating more ancient agricultural practices, earlier nucleated and sedentary villages, and longer and more intensive forest modification when compared with the Amazon. If we are to understand the history of tropical environments and how forest was originally lost to the human hand and can possibly be gained back, we have to also make these areas foci of our future endeavors.
See also: Human-Landscape Interactions; Paleoenvir-onmental Reconstruction, Methods; Phytolith Analysis; Pollen Analysis.
World History
