Nonlinear scaling of space use in human hunter–gatherers

Abstract

Use of space by both humans and other mammals should reflect underlying physiological, ecological, and behavioral processes. In particular, the space used by an individual for its normal activities should reflect the interplay of three constraints: (i) metabolic resource demand, (ii) environmental resource supply, and (iii) social behaviors that determine the extent to which space is used exclusively or shared with other individuals. In wild mammals, there is an allometric scaling relation between the home range of an individual and its body size: Larger mammals require more space per individual, but this relation is additionally modified by productivity of the environment, trophic niche, sociality, and ability to defend a territory [Kelt DA, Van home range ͉ macroecology ͉ scaling theory ͉ social networks T he ecology of all organisms is powerfully constrained by the exchange of energy and matter with the environment to meet metabolic resource demands. The ecology of human huntergatherers is particularly interesting, because social organization influences the uptake of energy, materials, and information from the environment and the distribution and transformation of these commodities within societies. Elsewhere we used HortonStrahler network theory to show how individual huntergatherers self-organize into social groups that facilitate the flow of fitness-related commodities among individuals at different hierarchical levels. The result is a complex social structure in which resources flow through social networks, which exhibit self-similar or fractal-like hierarchical scaling (M.J.H., B.T.M., R.S.W., and J.H.B., unpublished work) and are strikingly similar, quantitatively, to the hierarchically branched vascular networks that distribute metabolic resources within the bodies of plants (2, 3) and mammals (4, 5) and water within river drainage basins (6).Anthropologists have long been interested in the interplay of social structure, environmental conditions, and cultural factors on hunter-gatherer population size and demography (7-10). Here we investigate how the complex social networks of huntergatherer societies reflect the spatial and temporal scaling of rates of exchange of energy, matter, and information among individuals and how these interactions result in nonlinearities between human societies and their resource base. Well established macroecological scaling relations based on the first principles of physics, chemistry, and biology can account for much of the variation in the use of space by wild mammals. Here we ask how this framework must be modified to apply to traditional human societies.Like all biological species, human hunter-gatherers harvest energy and material resources from the environment to meet their metabolic requirements. For all mammals, including humans, energy requirements are set by whole-organism metabolic rate, B (in W), which scales with body size, M (in kg) as given by the following:where B 0 is a normalization constant. The scaling relation described by Eq. 1 holds greater than e...

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