Maya and Climate Climate has affected the vitality of many different societies in the past, as shown by numerous records across the globe and throughout human history. One of the most obvious and spectacular examples of this is from the Classic Maya civilization, whose advanced culture left highly detailed records of all aspects of their existence between 300 and 1000 C.E. Kennett et al. (p. 788 ; see the cover) present a detailed climate record derived from a stalagmite collected from a cave in Belize, in the midst of the Classic Maya settlement. The fine resolution and precise dating of the record allows changes in precipitation to be related to the politics, war, and population fluctuations of the Mayans.

Hill. He currently is working on a booklength analysis of the microecological bases of the hunter-gatherer mode of production.

Foraging models can predict the optimal diet selection for an organism which has the goal of maximizing its net acquisition rate for energy while hunting and gathering. Here a simulation methodology is used to determine the optimal diet selection under the assumption that the forager's goal is to minimize the risk of an energy shortfall. The results show that the rate-maximizing and risk-minimizing diets are similar; that sharing is more effective than changes in diet in reducing risk; and that the risk-reduction which can be obtained from sharing requires quite small numbers of participants. Food sharing may be an ancient and pervasive feature of hominid foraging adaptations.

a b s t r a c tThe prehistoric establishment and expansion of permanent settlements on the Northern Channel Islands of southern California generally follows a pattern predicted by the population ecology model, the ideal free distribution (IFD). We determine this by comparing the abundant archaeological record of these Islands against a careful quantification of habitat suitability using areal photography, satellite imagery, and field studies. We assess watershed area, length of rocky intertidal zone, length of sandy beach for plank canoe pull-outs and area of off-shore kelp beds, for 46 coastal locations. A simple descriptive analysis supports key IFD predictions. A Bayesian model fitted with the Gibbs sampler allows us to reconstruct the Native assessment of habitat that appears to underlie this process. Use of the Gibbs sampler mitigates the impact of missing data, censored variables, and uncertainty in radiocarbon dates; it allows us to predict where new settlements may yet be discovered. Theoretically, our results support a behavioral ecology interpretation of settlement history, human population expansion, and economic intensification in this region. They also demonstrate Bayesian analytical methods capable of making full use of the information available in archaeological datasets.Ó 2010 Elsevier Inc. All rights reserved. Introduction and problemThe Native Americans who moved from the mainland to settle the Northern Channel Islands of southern California knew well the country they were settling. By first recorded permanent settlement ($8000-7000 cal. years BP) they had been exploring and seasonally exploiting the resources of the islands for as much as 5000 years Kennett, 2005;. Subsequent to that first settlement further Island colonization of coastal sites at the mouths of major drainages drew on local knowledge gained through even more lengthy experience. Settlers were familiar with the suitability of the habitats they were about to occupy and, we might predict, they established residential sites in an orderly process of adaptive decision-making: Settle first in the most salubrious location. When, with growing exploitation or crowding, its resources were depressed and its value declined to match the next-ranked locale, establish a new settlement there. As population grew this process repeated, adding further new settlements in locations ordered by habitat suitability. In parallel, we expect overall quality of life in all occupied locales declined due to reductions in the availability of or access to critical resources. This process is neatly captured in a behavioral ecology model: the ideal free distribution (IFD, Fretwell and Lucas, 1969). Analysis of environmental and archaeological data from the Northern Channel Islands indicates that colonization there follows IFD predictions. To demonstrate this, we first describe the prehistory of the Northern Channel Islands. We then introduce the IFD, with the goal of predicting how population growth, intensified use and declining suitability generate a predictab...

Risk-sensitive analysis of subsistence adaptations is warranted when ( i) outcomes

In this paper we combine foraging theory and population biology models to simulate dynamic relationships between hunter-gatherers and their prey resources. Hunter-gatherer population growth responds to the net marginal rate of foraging; prey population growth responds logistically to exploitation. Thus conceived, the relationship between forager and prey biomass is time-dependent and nonlinear. It changes from stable equilibrium to damped and stable cycles with modest adjustments of input parameters. And, it produces the largest sustainable human population at intermediate levels of individual work effort. At equilibrium the forager takes all prey types with a pursuit and handling rate greater than or equal to its maintenance foraging rate. The structural properties of the model compel us to reject standard anthropological interpretations of the carrying capacity concept; they provide new insights on old issues such as original aflluence and intensification. Analysis of the interaction of human population, diet selection, and resource depletion requires microecological models in part because the relevant processes occur on time scales largely invisible to both ethnography and archaeology.

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Ugan, Bright and Rogers [When is technology worth the trouble? Journal of Archaeological Science 30 (10) (2003) 1315e1329] develop procurement and processing versions of an optimization model, termed the tech investment model, to formalize the conditions that favor investing time in the manufacture of more productive but more costly technologies. Their approach captures the tradeoffs that occur as less costly versions are supplanted by more costly versions of the same category of technology (e.g., fishhooks), but not the tradeoffs that occur when more costly categories of technology supplant different but less costly categories used for the same purpose (e.g., hook and line vs. spear). We (i) propose an alternative model in which different categories of technology are characterized by separate costebenefit curves, (ii) develop point-estimate and curve-estimate versions on this model, and (iii) show how they might be applied using the development of weaponry in aboriginal California as an example.