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  1. The northern American Southwest provides one of the most well-documented cases of human population growth and decline in the world. The geographic extent of this decline in North America is unknown owing to the lack of high-resolution palaeodemographic data from regions across and beyond the greater Southwest, where archaeological radiocarbon data are often the only available proxy for investigating these palaeodemographic processes. Radiocarbon time series across and beyond the greater Southwest suggest widespread population collapses from AD 1300 to 1600. However, radiocarbon data have potential biases caused by variable radiocarbon sample preservation, sample collection and the nonlinearity of the radiocarbonmore »calibration curve. In order to be confident in the wider trends seen in radiocarbon time series across and beyond the greater Southwest, here we focus on regions that have multiple palaeodemographic proxies and compare those proxies to radiocarbon time series. We develop a new method for time series analysis and comparison between dendrochronological data and radiocarbon data. Results confirm a multiple proxy decline in human populations across the Upland US Southwest, Central Mesa Verde and Northern Rio Grande from AD 1300 to 1600. These results lend confidence to single proxy radiocarbon-based reconstructions of palaeodemography outside the Southwest that suggest post-AD 1300 population declines in many parts of North America. This article is part of the theme issue ‘Cross-disciplinary approaches to prehistoric demography’.« less
  2. Questions regarding population stability among animals and plants are fundamental to population ecology, yet this has not been a topic studied by archeologists focusing on prehistoric human populations. This is an important knowledge gap. The fluctuation of human populations over decades to centuries – population instability – may constrain the expansion of human economies. A first step toward describing basic patterns of population stability would be to identify sizes of fluctuations through time, since smaller fluctuations are more stable than larger fluctuations. We conduct a biogeographic analysis of the long-term stability of human societies in North America using a continentalmore »scale radiocarbon dataset. Our analysis compares the stability of summed calibrated radiocarbon date probability distributions (SPDs) with subsistence strategies and modeled climate stability between 6000 and 300 BP. This coarse-grained analysis reveals general trends regarding the stability of human systems in North America that future studies may build upon. Our results demonstrate that agricultural sequences have more stable SPDs than hunter-gatherer sequences in general, but agricultural sequences also experience rare, extreme increases and decreases in SPDs not seen among hunter-gatherers. We propose that the adoption of agriculture has the unintended consequence of increasing population density and stability over most time scales, but also increases the vulnerability of populations to large, rare changes. Conversely, hunter-gatherer systems remain flexible and less vulnerable to large population changes. Climate stability may have an indirect effect on long-term population stability, and climate shocks may be buffered by other aspects of subsistence strategies prior to affecting human demography.« less
  3. On a planet experiencing global environmental change, the governance of natural resources depends on sustained collective action by diverse populations. Engaging in such collective action can only build upon the foundation of human cognition in social–ecological settings. To help understand this foundation, we assess the effect of cognitive abilities on the management of a common pool resource. We present evidence that two functionally distinct cognitive abilities, general and social intelligence, improve the ability of groups to manage a common pool resource. Groups high in both forms of intelligence engage in more effective collective action that is also more consistent, despitemore »social or ecological change. This result provides a foundation for integrating the effects of cognitive abilities with other dimensions of cognitive diversity to explain when groups will and will not sustainably govern natural resources.

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  4. Los modelos de lluvia impredecibles espacial y temporal presentaban desafíos de producción de cultivos agrícola por las comunidades, y requerían múltiples estrategias de mitigación de riesgos para aumentar la seguridad alimentaria. Si bien las investigaciones basadas en un sitio de la relación entre el clima y la producción agrícola ofrecen información sobre cómo las comunidades individuales pueden haber creado adaptaciones a largo plazo para gestionar el riesgo, la variabilidad espacial inherente del riesgo impulsado por el clima hace que una perspectiva a escala de paisaje sea valiosa. En este artículo, modelamos el riesgo evaluando cómo la estructura espacial de lasmore »condiciones climáticas antiguas puede haber afectado la confiabilidad de tres estrategias principales utilizadas para reducir el riesgo: aprovechar las redes sociales en tiempos de necesidad, cazar y recolectar recursos salvajes, y almacenar el excedente cultivos. Exploramos cómo los cambios climáticos en esta confiabilidad pueden relacionarse con las transformaciones sociales observadas arqueológicamente. Demostramos la utilidad de esta metodología al comparar las regiones de Salinas y Cibola en el sudoeste de los Estados Unidos prehispánico. Para comprender la relación entre los patrones climáticos a la seguridad alimentaria, analizamos las estrategias de mitigación de riesgos y las transformaciones sociales. Nuestros resultados sugieren diferencias críticas en la forma en que las comunidades protegieron contra el riesgo agrícola en las regiones de enfoque de Cibola y Salinas con la estructura de la precipitación que influye en el rango de estrategias a las que las comunidades tuvieron acceso a través del tiempo.« less
  5. Abstract Over the last decade, archaeologists have turned to large radiocarbon ( 14 C) data sets to infer prehistoric population size and change. An outstanding question concerns just how direct of an estimate 14 C dates are for human populations. In this paper we propose that 14 C dates are a better estimate of energy consumption, rather than an unmediated, proportional estimate of population size. We use a parametric model to describe the relationship between population size, economic complexity and energy consumption in human societies, and then parametrize the model using data from modern contexts. Our results suggest that energymore »consumption scales sub-linearly with population size, which means that the analysis of a large 14 C time-series has the potential to misestimate rates of population change and absolute population size. Energy consumption is also an exponential function of economic complexity. Thus, the 14 C record could change semi-independent of population as complexity grows or declines. Scaling models are an important tool for stimulating future research to tease apart the different effects of population and social complexity on energy consumption, and explain variation in the forms of 14 C date time-series in different regions.« less