Most authors consider 2,500 masl to be the critical threshold that defines a high elevation environment. Depending on the specific location in the Andes, these elevations may be extremely rugged with pronounced relief, such as the valleys of the western flanks of the Andes, or they may be relatively, flat, such as the vast expanse of the altiplano stretching from southern Ecuador well into northern Chile.
High mountain ecology is determined by a complex interaction of climate, elevation, and topography, and from a foraging perspective, this ecology can be characterized
Handbook of South American Archaeology, edited by Helaine Silverman and William H. Isbell.
Springer, New York, 2008
By five primary features (Aldenderfer 1998: 2-4): 1) environmental heterogeneity, 2) extremeness, 3) low predictability, 4) low primary productivity, and 5) high instability and fragility. High elevation environments tend to be patchy in both space and time, and consequently, there is significant variability in the location, size, and duration of resource patches. At high elevation, two aspects of extremeness are important: temperature and hypoxia. Even in tropical mountains like the Andes, cold is a constant problem. Humans must cope with cold by cultural adaptations that have significant material and energy costs, and thus divert resources from the subsistence quest. Hypoxia—the diminished availability of oxygen due to reduced barometric pressure at altitude—is a characteristic extreme of high mountain ecologies. Hypoxia affects plant morphology and metabolic processes, which in turn affects primary productivity. Humans, of course, are profoundly affected by hypoxia, and although our species has developed a number of physiological responses to it, it nevertheless remains the environmental extreme least amenable to cultural intervention.
In the Andes, low predictability describes the timing of onset of seasonal precipitation, which in turn has a significant effect on patch productivity and variability over time. The combination of cold, hypoxia, and aridity in the Andes creates a context of low primary productivity. Only the most extreme deserts and polar environments of the planet have lower primary productivity than those at high elevation. Finally, high elevation environments are highly susceptible to wind and rain erosion and extreme colluvial processes that can modify terrain, change stream courses, and destroy resource patches, thus contributing to the overall patchiness of the high elevation landscape. In short, foragers who lived at high elevation in the Andes were faced with a series of environmental challenges that profoundly shaped the course of cultural evolution and process.
The two primary extremes of high elevation environments—hypoxia and cold— act as stressors on human biology, and affect all facets of life, especially reproduction, growth, health status, morbidity, mortality, nutritional status, and work effort. Although the existing indigenous people of the Andes have a variety of physiological acclimatizations that ameliorate the negative effects of hypoxia, these developed over time, in response to pressures that must have acted as constraints on the earliest inhabitants of the Andes and their descendants. A consideration of these stressors is necessary because they have had a significant effect on the range of human cultural adaptations and historical outcomes of cultural evolution and change at high altitude. Constraints on fertility or exceptionally high neonatal mortality rates, for example, which are known to affect migrants to high elevation (Willey 2004), may well have led to lower growth rates of highland populations, especially in the generations immediately following their founding by lowlanders. And since high elevation peoples tend to have higher basal metabolic rates, they would have required on average more calories than comparable low-elevation peoples. In turn, this may have had important effects on cultural strategies when dealing with problems relating to environmental packing, diet choice under restricted mobility, resource intensification, and both short - and long-term changes in resource availability. Mobility strategies themselves may have been substantially affected due to demands imposed by basic caloric requirements as well as the greater work effort required to traverse rugged mountain topography. Although it is important not to cast these stressors in an overly deterministic role, they did have tangible effects on a variety of aspects of human life at high elevation.
World History
