I am a human ecologist with training in anthropology, archaeology and ecology. My research program combines the comparison of ethnographic and archaeological data, formal models of social and ecological systems and contextualized behavioral experiments to identify and evaluate general principles of human-environment interactions. I specifically investigate the evolution of resource ownership and territoriality among hunter-gatherers, the adoption of domesticated plants by hunter-gatherers, agricultural specialization and how diversity impacts the long-term robustness of coupled social and ecological systems.
Proceedings of the National Academy of Sciences of the United States of America, Oct 2, 2018
We conduct a global comparison of the consumption of energy by human populations throughout the H... more We conduct a global comparison of the consumption of energy by human populations throughout the Holocene and statistically quantify coincident changes in the consumption of energy over space and time-an ecological phenomenon known as synchrony. When populations synchronize, adverse changes in ecosystems and social systems may cascade from society to society. Thus, to develop policies that favor the sustained use of resources, we must understand the processes that cause the synchrony of human populations. To date, it is not clear whether human societies display long-term synchrony or, if they do, the potential causes. Our analysis begins to fill this knowledge gap by quantifying the long-term synchrony of human societies, and we hypothesize that the synchrony of human populations results from () the creation of social ties that couple populations over smaller scales and () much larger scale, globally convergent trajectories of cultural evolution toward more energy-consuming political...
Explaining the stability of human populations provides knowledge for understanding the resilience... more Explaining the stability of human populations provides knowledge for understanding the resilience of human societies to environmental change. Here, we use archaeological radiocarbon records to evaluate a hypothesis drawn from resilience thinking that may explain the stability of human populations: Faced with long-term increases in population density, greater variability in the production of food leads to less stable populations, while lower variability leads to more stable populations. However, increased population stability may come with the cost of larger collapses in response to rare, large-scale environmental perturbations. Our results partially support this hypothesis. Agricultural societies that relied on extensive landscape engineering to intensify production and tightly control variability in the production of food experienced the most stability. Contrary to the hypothesis, these societies also experienced the least severe population declines. We propose that the interrelationship between landscape engineering and increased political-economic complexity reduces the magnitude of population collapses in a region.
Describing and explaining the population growth trajectories of prehistoric hunter-gatherers is a... more Describing and explaining the population growth trajectories of prehistoric hunter-gatherers is an important research problem. Large radiocarbon data sets provide one empirical starting point for describing these trajectories; however, explaining trajectories of growth must always take place within the context of theory. In this paper, we formalize a ratchet model of long-term, mean population growth among hunter-gatherers and evaluate the plausibility of that model using two extensive radiocarbon data sets from Central Texas and the Texas Coastal Plain. Our analysis suggests that hunter-gatherer populations in these regions displayed waves of population growth separated by periods of population saturation and competition for resources. Our model and results suggest that hunter-gatherer populations in Texas may have experienced multiple demographic transitions to successively higher levels of population saturation (carrying capacity). Our results derive from a general model, a set of methods applicable across archaeological regions, and provide a basis for hypotheses that may explain changes in the socioecology of hunter-gatherers.
Explaining variation in human population density constitutes a basic research problem in human ec... more Explaining variation in human population density constitutes a basic research problem in human ecology and archaeological science. To contribute to this basic research problem, we build a graphic model and conduct a global analysis of the effects of ecological variables, controlling for technological differences, on human population density. Our results indicate that human population densities display a consistent relationship with ecological variables across productive technologies. Human population densities peak in high productivity environments with moderate levels of species richness and moderate to low levels of pathogens among hunter-gatherer, subsistence agricultural, and industrial societies. Population densities are lower in low productivity environments as well as environments with high productivity, high species richness and high pathogen loads. Productive technology shifts to agriculture and industrial production impact human population densities more than ecological variables, and such shifts toward agriculture or industrial production may weaken the effect of net primary productivity on population density. These results illustrate the nature of the relationship between population density and ecological variables, which are partly driven by climate, and the results provide a basis for hypotheses that researchers can use to analyze the potential effects of climate change on material record estimates of human paleo-population density.
Comparative social science has a long history of attempts to classify societies and cultures in t... more Comparative social science has a long history of attempts to classify societies and cultures in terms of shared characteristics. However, only recently has it become feasible to conduct quantitative analysis of large historical datasets to mathematically approach the study of social complexity and classify shared societal characteristics. Such methods have the potential to identify recurrent social formations in human societies and contribute to social evolutionary theory. However, in order to achieve this potential, repeated studies are needed to assess the robustness of results to changing methods and data sets. Using an improved derivative of the Seshat: Global History Databank, we perform a clustering analysis of 271 past societies from sampling points across the globe to study plausible cate-gorizations inherent in the data. Analysis indicates that the best fit to Seshat data is five sub-clusters existing as part of two clearly delineated superclusters (that is, two broad "types" of society in terms of social-ecological configuration). Our results add weight to the idea that human societies form recurrent social formations by replicating previous studies with different methods and data. Our results also contribute nuance to previously established measures of social complexity, illustrate diverse trajectories of change, and shed further light on the finite bounds of human social diversity.
Proceedings of the National Academy of Sciences, 2020
On a planet experiencing global environmental change, the gover-nance of natural resources depend... more On a planet experiencing global environmental change, the gover-nance 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, despite 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.
Taking inspiration from the archaeology of the Texas Coastal Plain (TCP), we develop an ecologica... more Taking inspiration from the archaeology of the Texas Coastal Plain (TCP), we develop an ecological theory of population distribution among mobile hunter-gatherers. This theory proposes that, due to the heterogeneity of resources in space and time, foragers create networks of habitats that they access through residential cycling and shared knowledge. The degree of cycling that individuals exhibit in creating networks of habitats, encoded through social relationships, depends on the relative scarcity of resources and fluctuations in those resources. Using a dynamic model of hunter-gatherer population distribution, we illustrate that increases in population density, coupled with shocks to a biophysical or social system, creates a selective environment that favors habitat partitioning and investments in social mechanisms that control the residential cycling of foragers on a landscape. Our work adds a layer of realism to Ideal Distribution Models by adding a time allocation decision process in a variable environment and illustrates a general variance reduction, safe-operating space tradeoff among mobile human foragers that drives social change.
Cognitive abilities underpin the capacity of individuals to build models of their environment and... more Cognitive abilities underpin the capacity of individuals to build models of their environment and make decisions about how to govern resources. Here, we test the functional intelligences proposition that functionally diverse cognitive abilities within a group are critical to govern common pool resources. We assess the effect of two cognitive abilities, social and general intelligence, on group performance on a resource harvesting and management game involving either a negative or a positive disturbance to the resource base. Our results indicate that under improving conditions (positive disturbance) groups with higher general intelligence perform better. However, when conditions deteriorate (negative disturbance) groups with high competency in both general and social intelligence are less likely to deplete resources and harvest more. Thus, we propose that a functional diversity of cognitive abilities improves how effectively social groups govern common pool resources, especially when conditions deteriorate and groups need to re-evaluate and change their behaviors.
We conduct a global comparison of the consumption of energy by human populations throughout the H... more We conduct a global comparison of the consumption of energy by human populations throughout the Holocene and statistically quantify coincident changes in the consumption of energy over space and time—an ecological phenomenon known as synchrony. When populations synchronize, adverse changes in ecosystems and social systems may cascade from society to society. Thus, to develop policies that favor the sustained use of resources, we must understand the processes that cause the synchrony of human populations. To date, it is not clear whether human societies display long-term synchrony or, if they do, the potential causes. Our analysis begins to fill this knowledge gap by quantifying the long-term synchrony of human societies, and we hypothesize that the synchrony of human populations results from (i) the creation of social ties that couple populations over smaller scales and (ii) much larger scale, globally convergent tra-jectories of cultural evolution toward more energy-consuming political economies with higher carrying capacities. Our results suggest that the process of globalization is a natural consequence of evolutionary trajectories that increase the carrying capacities of human societies.
A basic premise of economics is that more secure property rights reduce conflict and provide an i... more A basic premise of economics is that more secure property rights reduce conflict and provide an incentive for individuals to increase the productivity of their land. This premise underlies recent theories that food production and more secure property rights, by necessity, co-evolve. The argument goes like this: Dense and predicable resources provide an incentive for more secure property rights and more secure property rights provide an incentive for individuals to modify ecosystems in ways that increase the production of food. Here, we evaluate the effect of property rights on food production among ethnographically recorded hunter-gatherers. In particular, we use path models to evaluate a recent theory for the evolution of ownership rights and ecosystem management in forager-resource systems called the Niche Construction Model of Economic Defense. We conclude that ownership has a positive effect on food production strategies that require reduced coordination between individuals (such as planting and tending patches), but potentially has a negative effect on other food production strategies such as landscape burning. Further, the coefficient of variation in rainfall and population density consistently have positive effects on the presence of food production. We discuss the implications of our results for explaining different trajectories of hunter-gatherer intensification in the archaeological record.
Over the last decade, archaeologists have turned to large radiocarbon (14 C) data sets to infer p... more 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 energy 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.
We evaluate two models that may explain variation in the inclusiveness of governments and their a... more We evaluate two models that may explain variation in the inclusiveness of governments and their ability to provision public goods. The revenue model predicts that a government's source of revenue determines whether elites invest in effective bureaucracy and the provision of public goods that benefit wide swaths of society or the extraction of resources from society to benefit a limited network. In this model, a cooperative society with high social capital is an outcome of effective, collective government. The combined model predicts that social capital has a semi-independent causal effect, in addition to revenue, on the inclusiveness of governments. Our results indicate that the combined model of collective governance fits the data on U.S. states better than the revenue model alone. The combined model of governance predicts that revenue and social capital moderate the population size–political complexity relationship, and data from the U.S. states are consistent with these predictions.
Tradeoffs make win-win scenarios difficult to achieve in social-ecological systems (SES). But it ... more Tradeoffs make win-win scenarios difficult to achieve in social-ecological systems (SES). But it is one thing to recognize that tradeoffs make win-wins difficult to achieve and quite another to understand the interaction of factors in social-ecological systems that generate tradeoffs, and the kinds of tradeoffs that may preclude win-wins. In this paper we investigate the effects of individuals with diverse capabilities on the ability of social actors to achieve win-wins with a model of agricultural specialization and exchange. Our model is inspired by the northern frontier of Mesoamerica, which experienced rapid development around 500 CE and then rapid decline 900-1000 CE. We show that sometimes actors with diverse capabilities experience equity-inequity tradeoffs that may constrain collective action, lead to social dissruption, and limit win-wins. We propose categories of tradeofss in SES that may constrain win-wins.
The adaptive cycle, a seminal component of resilience theory, is a powerful model that archaeolog... more The adaptive cycle, a seminal component of resilience theory, is a powerful model that archaeologists use to understand the persistence and transformation of prehistoric societies. In this paper, we argue that resilience theory will have a more enduring explanatory role in archaeology if scholars can build on the initial insights of the adaptive cycle model and create more contextualized hypotheses of social-ecological change. By contextualized hypotheses we mean testable hypotheses that specify: (1) the form of the connections among people and ecological elements and how those connections change; and (2) the resilience-vulnerability tradeoffs associated with changes in the networks and institutions that link social and ecological processes. To develop such a contextualized hypothesis, we combine our knowledge of the prehistory of the Texas Coastal Plain (TCP), mathematical modeling, and the concept of panarchy to study why human societies successfully cope with the interrelated forces of globalization, population growth, and climate change, and, sometimes, fail to cope with these interrelated forces. Our hypothesis is that, in response to population growth, hunter-gatherers on the TCP created increasingly dense social networks that allowed individuals to maintain residual access to important sources of food. While this was a good strategy for individuals to maintain a reliable supply of food in a variable environment , increasingly elaborate social networks created a panarchy of reachable forager-resource systems. The panarchy of forager-resource systems on the TCP created a hidden fragility: The potential for the failure of resources in one system to cascade from system-to-system across the entire TCP. We propose that this occurred around 700 years BP, causing a 6000 year old ritual and mortuary complex to reorganize.
This paper combines theory from ecology and anthropology to investigate variation in the territor... more This paper combines theory from ecology and anthropology to investigate variation in the territory sizes of subsistence oriented agricultural societies. The results indicate that population and the dependence of individuals within a society on " wild " foods partly determine the territory sizes of agricultural societies. In contrast, the productivity of an agroecosystem is not an important determinant of territory size. A comparison of the population-territory size scaling dynamics of agricultural societies and human foragers indicates that foragers and farmers face the same constraints on their ability to expand their territory and intensify their use of resources within a territory. However, the higher density of food in an agroecosystem allows farmers, on average, to live at much higher population densities than human foragers. These macroecological patterns are consistent with a " work-around hypothesis " for the adoption of farming. This hypothesis is that as residential groups of foragers increase in size, farming can sometimes better reduce the tension between an individual's autonomy over resources and the need for social groups to function to provide public goods like defense and information.
The evolution of agricultural economies requires two processes: 1) the domestication of plants an... more The evolution of agricultural economies requires two processes: 1) the domestication of plants and 2) specialization in agricultural practices at the expense of alternative subsistence pursuits. Yet, in the literature, domestication receives the lion's share of attention while theories of specialization lag behind. In this paper, we integrate ideas from human behavioral ecology (HBE) with tools from dynamical systems theory to study the effects of ecological inheritance on levels of investment in foraging and farming. Ecological inheritance is an outcome of niche construction and our study provides a formal link between foraging theory and niche construction. Our analysis of a dynamic model of foraging and farming illustrates that the optimal allocation of effort to foraging and farming can lead to the emergence of multiple stable states. The consequence of this is that low-level farming optimizes subsistence (e.g., minimizing the effort required to meet a subsistence goal) in a forager-resource system over a few years but makes the whole system vulnerable to punctuated change over decades due to rare events. We use the insights of our model to propose a general ecological framework to explain the evolution and diversity of transitions from foraging to farming. Link to Final: http://authors.elsevier.com/a/1RS9W-JVbUUYA
Why are some governments more effective managers of resources–people, places and finances–and oth... more Why are some governments more effective managers of resources–people, places and finances–and others less effective? This question is at the center of understanding political and economic development. Yet, established theory that explains how individual cognitive differences and sociological forces mutually explain government effectiveness is lacking. To bridge this knowledge gap we articulate the Functional Intelligences Proposition (FIP): The individual level attributes of general intelligence and social intelligence serve unique information processing functions and have a positive and independent effect on the ability of individuals, acting in concert, to govern resources. To begin to evaluate the FIP, we study the effects of general intelligence, social intelligence and social infrastructure (prosocial norms & trust) on how effectively US states govern. We find that measures of general intelligence (estimated by IQ) and social intelligence (social-cognitive theory of mind– ToM–estimated by agreeableness) have a positive and independent effect on the effectiveness of governance. The FIP provides an interdisciplinary explanation for the effectiveness of governance and, ultimately, development.
This paper contributes to understanding the socioecology of
hunter-gatherer territorial dynamics... more This paper contributes to understanding the socioecology of
hunter-gatherer territorial dynamics. We develop and evaluate three hypotheses for the effects of corporate territorial ownership and the storage of food on the territory size of hunter-gatherer societies. We seek to initiate a more nuanced understanding of how social and technological organization cause and constrain the size of hunter-gatherer territories, in addition to the factors of population size and the productivity of ecosystems documented among primates and mammals in general. Our analysis suggests that the storage of food fundamentally alters population-territory size dynamics in hunter-gatherer societies. When societies store food, territory size is a sub-linear function of population. When societies do not store food, the function is approximately linear. The sub-linear scaling of population and territory size indicates that when societies store food, the social units that comprise ethno-linguistic groups produce
more food per unit of area and share ever more over-lapping
subsistence ranges in response to population growth. This non-linear population-territory size relationship signals that coevolutionary processes initiated by different ways of constructing a niche generate diversity in hunter-gatherer societies. We speculate that the storage of food, initiated to cope with the short-term risk of a short-fall of food, has long-term consequences on the trajectory of hunter-gatherer
evolution in general.
Freeman, J., Anderies, J. M., 2015. A comparative ethnoarchaeological analysis of corporate terri... more Freeman, J., Anderies, J. M., 2015. A comparative ethnoarchaeological analysis of corporate territorial ownership. Journal of Archaeological Science 54, 135–147. URL:http://www.sciencedirect.com/science/article/pii/ S0305440314004506
Ecological models are a fundamental tool that archaeologists use to clarify our thinking about the processes that generate the archaeological record. Typically, arguments reasoned from a single model are bolstered by observing the consistency of ethnographic data with the argument. This is often referred to as model validation, and establishes that an argument is reasonable. In this paper, we move beyond validation by comparing the consistency of two arguments reasoned from different models that may explain corporate territorial ownership with data from a large sample of ethnographic cases. Our results suggest that social dilemmas are an under appreciated mechanism that can drive the evolution of corporate territorial ownership. When social dilemmas emerge, the costs associated with provisioning the public goods of information on resources or, perhaps, common defense create situations in which human foragers gain more by cooperating to recognize corporate ownership rules than they lose. Our results also indicate that societies who share a common cultural history are more
likely to recognize corporate ownership, and there is a spatial dynamic in which societies who live near each other are more likely to recognize corporate ownership as the number of near-by groups who recognize ownership increases. Our results have important implications for investigating the
coevolution of territorial ownership and the adoption of food production in the archaeological record.
Diversity is generally valued, although it sometimes contributes to difficult social situations, ... more Diversity is generally valued, although it sometimes contributes to difficult social situations, as is recognized in recent social science literature. Archaeology can provide insights into how diverse social situations play out over the long term. There are many kinds of diversities, and we propose representational diversity as a distinct category. Representational diversity specifically concerns how and whether differences are marked or masked materially. We investigate several archaeological sequences in the U.S. Southwest. Each began with the coming together of populations that created situations of unprecedented social diversity; some resulted in conflict, others in long-term stability. We trace how representational diversity changed through these sequences. Specifically, we review the transregional Kayenta migration to the southern Southwest and focus empirical analyses on regional processes in the Cibola region and on painted ceramics. Results show that, initially, representational diversity increased above and beyond that caused by the combination of previously separate traditions as people marked their differences. Subsequently, in some instances, the diversity was replaced by widespread homogeneity as the differences were masked and mitigated. Although the social causes and effects of diversity are many and varied, long-term stability and persistence is associated with tolerance of a range of diversities.
Proceedings of the National Academy of Sciences of the United States of America, Oct 2, 2018
We conduct a global comparison of the consumption of energy by human populations throughout the H... more We conduct a global comparison of the consumption of energy by human populations throughout the Holocene and statistically quantify coincident changes in the consumption of energy over space and time-an ecological phenomenon known as synchrony. When populations synchronize, adverse changes in ecosystems and social systems may cascade from society to society. Thus, to develop policies that favor the sustained use of resources, we must understand the processes that cause the synchrony of human populations. To date, it is not clear whether human societies display long-term synchrony or, if they do, the potential causes. Our analysis begins to fill this knowledge gap by quantifying the long-term synchrony of human societies, and we hypothesize that the synchrony of human populations results from () the creation of social ties that couple populations over smaller scales and () much larger scale, globally convergent trajectories of cultural evolution toward more energy-consuming political...
Explaining the stability of human populations provides knowledge for understanding the resilience... more Explaining the stability of human populations provides knowledge for understanding the resilience of human societies to environmental change. Here, we use archaeological radiocarbon records to evaluate a hypothesis drawn from resilience thinking that may explain the stability of human populations: Faced with long-term increases in population density, greater variability in the production of food leads to less stable populations, while lower variability leads to more stable populations. However, increased population stability may come with the cost of larger collapses in response to rare, large-scale environmental perturbations. Our results partially support this hypothesis. Agricultural societies that relied on extensive landscape engineering to intensify production and tightly control variability in the production of food experienced the most stability. Contrary to the hypothesis, these societies also experienced the least severe population declines. We propose that the interrelationship between landscape engineering and increased political-economic complexity reduces the magnitude of population collapses in a region.
Describing and explaining the population growth trajectories of prehistoric hunter-gatherers is a... more Describing and explaining the population growth trajectories of prehistoric hunter-gatherers is an important research problem. Large radiocarbon data sets provide one empirical starting point for describing these trajectories; however, explaining trajectories of growth must always take place within the context of theory. In this paper, we formalize a ratchet model of long-term, mean population growth among hunter-gatherers and evaluate the plausibility of that model using two extensive radiocarbon data sets from Central Texas and the Texas Coastal Plain. Our analysis suggests that hunter-gatherer populations in these regions displayed waves of population growth separated by periods of population saturation and competition for resources. Our model and results suggest that hunter-gatherer populations in Texas may have experienced multiple demographic transitions to successively higher levels of population saturation (carrying capacity). Our results derive from a general model, a set of methods applicable across archaeological regions, and provide a basis for hypotheses that may explain changes in the socioecology of hunter-gatherers.
Explaining variation in human population density constitutes a basic research problem in human ec... more Explaining variation in human population density constitutes a basic research problem in human ecology and archaeological science. To contribute to this basic research problem, we build a graphic model and conduct a global analysis of the effects of ecological variables, controlling for technological differences, on human population density. Our results indicate that human population densities display a consistent relationship with ecological variables across productive technologies. Human population densities peak in high productivity environments with moderate levels of species richness and moderate to low levels of pathogens among hunter-gatherer, subsistence agricultural, and industrial societies. Population densities are lower in low productivity environments as well as environments with high productivity, high species richness and high pathogen loads. Productive technology shifts to agriculture and industrial production impact human population densities more than ecological variables, and such shifts toward agriculture or industrial production may weaken the effect of net primary productivity on population density. These results illustrate the nature of the relationship between population density and ecological variables, which are partly driven by climate, and the results provide a basis for hypotheses that researchers can use to analyze the potential effects of climate change on material record estimates of human paleo-population density.
Comparative social science has a long history of attempts to classify societies and cultures in t... more Comparative social science has a long history of attempts to classify societies and cultures in terms of shared characteristics. However, only recently has it become feasible to conduct quantitative analysis of large historical datasets to mathematically approach the study of social complexity and classify shared societal characteristics. Such methods have the potential to identify recurrent social formations in human societies and contribute to social evolutionary theory. However, in order to achieve this potential, repeated studies are needed to assess the robustness of results to changing methods and data sets. Using an improved derivative of the Seshat: Global History Databank, we perform a clustering analysis of 271 past societies from sampling points across the globe to study plausible cate-gorizations inherent in the data. Analysis indicates that the best fit to Seshat data is five sub-clusters existing as part of two clearly delineated superclusters (that is, two broad "types" of society in terms of social-ecological configuration). Our results add weight to the idea that human societies form recurrent social formations by replicating previous studies with different methods and data. Our results also contribute nuance to previously established measures of social complexity, illustrate diverse trajectories of change, and shed further light on the finite bounds of human social diversity.
Proceedings of the National Academy of Sciences, 2020
On a planet experiencing global environmental change, the gover-nance of natural resources depend... more On a planet experiencing global environmental change, the gover-nance 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, despite 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.
Taking inspiration from the archaeology of the Texas Coastal Plain (TCP), we develop an ecologica... more Taking inspiration from the archaeology of the Texas Coastal Plain (TCP), we develop an ecological theory of population distribution among mobile hunter-gatherers. This theory proposes that, due to the heterogeneity of resources in space and time, foragers create networks of habitats that they access through residential cycling and shared knowledge. The degree of cycling that individuals exhibit in creating networks of habitats, encoded through social relationships, depends on the relative scarcity of resources and fluctuations in those resources. Using a dynamic model of hunter-gatherer population distribution, we illustrate that increases in population density, coupled with shocks to a biophysical or social system, creates a selective environment that favors habitat partitioning and investments in social mechanisms that control the residential cycling of foragers on a landscape. Our work adds a layer of realism to Ideal Distribution Models by adding a time allocation decision process in a variable environment and illustrates a general variance reduction, safe-operating space tradeoff among mobile human foragers that drives social change.
Cognitive abilities underpin the capacity of individuals to build models of their environment and... more Cognitive abilities underpin the capacity of individuals to build models of their environment and make decisions about how to govern resources. Here, we test the functional intelligences proposition that functionally diverse cognitive abilities within a group are critical to govern common pool resources. We assess the effect of two cognitive abilities, social and general intelligence, on group performance on a resource harvesting and management game involving either a negative or a positive disturbance to the resource base. Our results indicate that under improving conditions (positive disturbance) groups with higher general intelligence perform better. However, when conditions deteriorate (negative disturbance) groups with high competency in both general and social intelligence are less likely to deplete resources and harvest more. Thus, we propose that a functional diversity of cognitive abilities improves how effectively social groups govern common pool resources, especially when conditions deteriorate and groups need to re-evaluate and change their behaviors.
We conduct a global comparison of the consumption of energy by human populations throughout the H... more We conduct a global comparison of the consumption of energy by human populations throughout the Holocene and statistically quantify coincident changes in the consumption of energy over space and time—an ecological phenomenon known as synchrony. When populations synchronize, adverse changes in ecosystems and social systems may cascade from society to society. Thus, to develop policies that favor the sustained use of resources, we must understand the processes that cause the synchrony of human populations. To date, it is not clear whether human societies display long-term synchrony or, if they do, the potential causes. Our analysis begins to fill this knowledge gap by quantifying the long-term synchrony of human societies, and we hypothesize that the synchrony of human populations results from (i) the creation of social ties that couple populations over smaller scales and (ii) much larger scale, globally convergent tra-jectories of cultural evolution toward more energy-consuming political economies with higher carrying capacities. Our results suggest that the process of globalization is a natural consequence of evolutionary trajectories that increase the carrying capacities of human societies.
A basic premise of economics is that more secure property rights reduce conflict and provide an i... more A basic premise of economics is that more secure property rights reduce conflict and provide an incentive for individuals to increase the productivity of their land. This premise underlies recent theories that food production and more secure property rights, by necessity, co-evolve. The argument goes like this: Dense and predicable resources provide an incentive for more secure property rights and more secure property rights provide an incentive for individuals to modify ecosystems in ways that increase the production of food. Here, we evaluate the effect of property rights on food production among ethnographically recorded hunter-gatherers. In particular, we use path models to evaluate a recent theory for the evolution of ownership rights and ecosystem management in forager-resource systems called the Niche Construction Model of Economic Defense. We conclude that ownership has a positive effect on food production strategies that require reduced coordination between individuals (such as planting and tending patches), but potentially has a negative effect on other food production strategies such as landscape burning. Further, the coefficient of variation in rainfall and population density consistently have positive effects on the presence of food production. We discuss the implications of our results for explaining different trajectories of hunter-gatherer intensification in the archaeological record.
Over the last decade, archaeologists have turned to large radiocarbon (14 C) data sets to infer p... more 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 energy 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.
We evaluate two models that may explain variation in the inclusiveness of governments and their a... more We evaluate two models that may explain variation in the inclusiveness of governments and their ability to provision public goods. The revenue model predicts that a government's source of revenue determines whether elites invest in effective bureaucracy and the provision of public goods that benefit wide swaths of society or the extraction of resources from society to benefit a limited network. In this model, a cooperative society with high social capital is an outcome of effective, collective government. The combined model predicts that social capital has a semi-independent causal effect, in addition to revenue, on the inclusiveness of governments. Our results indicate that the combined model of collective governance fits the data on U.S. states better than the revenue model alone. The combined model of governance predicts that revenue and social capital moderate the population size–political complexity relationship, and data from the U.S. states are consistent with these predictions.
Tradeoffs make win-win scenarios difficult to achieve in social-ecological systems (SES). But it ... more Tradeoffs make win-win scenarios difficult to achieve in social-ecological systems (SES). But it is one thing to recognize that tradeoffs make win-wins difficult to achieve and quite another to understand the interaction of factors in social-ecological systems that generate tradeoffs, and the kinds of tradeoffs that may preclude win-wins. In this paper we investigate the effects of individuals with diverse capabilities on the ability of social actors to achieve win-wins with a model of agricultural specialization and exchange. Our model is inspired by the northern frontier of Mesoamerica, which experienced rapid development around 500 CE and then rapid decline 900-1000 CE. We show that sometimes actors with diverse capabilities experience equity-inequity tradeoffs that may constrain collective action, lead to social dissruption, and limit win-wins. We propose categories of tradeofss in SES that may constrain win-wins.
The adaptive cycle, a seminal component of resilience theory, is a powerful model that archaeolog... more The adaptive cycle, a seminal component of resilience theory, is a powerful model that archaeologists use to understand the persistence and transformation of prehistoric societies. In this paper, we argue that resilience theory will have a more enduring explanatory role in archaeology if scholars can build on the initial insights of the adaptive cycle model and create more contextualized hypotheses of social-ecological change. By contextualized hypotheses we mean testable hypotheses that specify: (1) the form of the connections among people and ecological elements and how those connections change; and (2) the resilience-vulnerability tradeoffs associated with changes in the networks and institutions that link social and ecological processes. To develop such a contextualized hypothesis, we combine our knowledge of the prehistory of the Texas Coastal Plain (TCP), mathematical modeling, and the concept of panarchy to study why human societies successfully cope with the interrelated forces of globalization, population growth, and climate change, and, sometimes, fail to cope with these interrelated forces. Our hypothesis is that, in response to population growth, hunter-gatherers on the TCP created increasingly dense social networks that allowed individuals to maintain residual access to important sources of food. While this was a good strategy for individuals to maintain a reliable supply of food in a variable environment , increasingly elaborate social networks created a panarchy of reachable forager-resource systems. The panarchy of forager-resource systems on the TCP created a hidden fragility: The potential for the failure of resources in one system to cascade from system-to-system across the entire TCP. We propose that this occurred around 700 years BP, causing a 6000 year old ritual and mortuary complex to reorganize.
This paper combines theory from ecology and anthropology to investigate variation in the territor... more This paper combines theory from ecology and anthropology to investigate variation in the territory sizes of subsistence oriented agricultural societies. The results indicate that population and the dependence of individuals within a society on " wild " foods partly determine the territory sizes of agricultural societies. In contrast, the productivity of an agroecosystem is not an important determinant of territory size. A comparison of the population-territory size scaling dynamics of agricultural societies and human foragers indicates that foragers and farmers face the same constraints on their ability to expand their territory and intensify their use of resources within a territory. However, the higher density of food in an agroecosystem allows farmers, on average, to live at much higher population densities than human foragers. These macroecological patterns are consistent with a " work-around hypothesis " for the adoption of farming. This hypothesis is that as residential groups of foragers increase in size, farming can sometimes better reduce the tension between an individual's autonomy over resources and the need for social groups to function to provide public goods like defense and information.
The evolution of agricultural economies requires two processes: 1) the domestication of plants an... more The evolution of agricultural economies requires two processes: 1) the domestication of plants and 2) specialization in agricultural practices at the expense of alternative subsistence pursuits. Yet, in the literature, domestication receives the lion's share of attention while theories of specialization lag behind. In this paper, we integrate ideas from human behavioral ecology (HBE) with tools from dynamical systems theory to study the effects of ecological inheritance on levels of investment in foraging and farming. Ecological inheritance is an outcome of niche construction and our study provides a formal link between foraging theory and niche construction. Our analysis of a dynamic model of foraging and farming illustrates that the optimal allocation of effort to foraging and farming can lead to the emergence of multiple stable states. The consequence of this is that low-level farming optimizes subsistence (e.g., minimizing the effort required to meet a subsistence goal) in a forager-resource system over a few years but makes the whole system vulnerable to punctuated change over decades due to rare events. We use the insights of our model to propose a general ecological framework to explain the evolution and diversity of transitions from foraging to farming. Link to Final: http://authors.elsevier.com/a/1RS9W-JVbUUYA
Why are some governments more effective managers of resources–people, places and finances–and oth... more Why are some governments more effective managers of resources–people, places and finances–and others less effective? This question is at the center of understanding political and economic development. Yet, established theory that explains how individual cognitive differences and sociological forces mutually explain government effectiveness is lacking. To bridge this knowledge gap we articulate the Functional Intelligences Proposition (FIP): The individual level attributes of general intelligence and social intelligence serve unique information processing functions and have a positive and independent effect on the ability of individuals, acting in concert, to govern resources. To begin to evaluate the FIP, we study the effects of general intelligence, social intelligence and social infrastructure (prosocial norms & trust) on how effectively US states govern. We find that measures of general intelligence (estimated by IQ) and social intelligence (social-cognitive theory of mind– ToM–estimated by agreeableness) have a positive and independent effect on the effectiveness of governance. The FIP provides an interdisciplinary explanation for the effectiveness of governance and, ultimately, development.
This paper contributes to understanding the socioecology of
hunter-gatherer territorial dynamics... more This paper contributes to understanding the socioecology of
hunter-gatherer territorial dynamics. We develop and evaluate three hypotheses for the effects of corporate territorial ownership and the storage of food on the territory size of hunter-gatherer societies. We seek to initiate a more nuanced understanding of how social and technological organization cause and constrain the size of hunter-gatherer territories, in addition to the factors of population size and the productivity of ecosystems documented among primates and mammals in general. Our analysis suggests that the storage of food fundamentally alters population-territory size dynamics in hunter-gatherer societies. When societies store food, territory size is a sub-linear function of population. When societies do not store food, the function is approximately linear. The sub-linear scaling of population and territory size indicates that when societies store food, the social units that comprise ethno-linguistic groups produce
more food per unit of area and share ever more over-lapping
subsistence ranges in response to population growth. This non-linear population-territory size relationship signals that coevolutionary processes initiated by different ways of constructing a niche generate diversity in hunter-gatherer societies. We speculate that the storage of food, initiated to cope with the short-term risk of a short-fall of food, has long-term consequences on the trajectory of hunter-gatherer
evolution in general.
Freeman, J., Anderies, J. M., 2015. A comparative ethnoarchaeological analysis of corporate terri... more Freeman, J., Anderies, J. M., 2015. A comparative ethnoarchaeological analysis of corporate territorial ownership. Journal of Archaeological Science 54, 135–147. URL:http://www.sciencedirect.com/science/article/pii/ S0305440314004506
Ecological models are a fundamental tool that archaeologists use to clarify our thinking about the processes that generate the archaeological record. Typically, arguments reasoned from a single model are bolstered by observing the consistency of ethnographic data with the argument. This is often referred to as model validation, and establishes that an argument is reasonable. In this paper, we move beyond validation by comparing the consistency of two arguments reasoned from different models that may explain corporate territorial ownership with data from a large sample of ethnographic cases. Our results suggest that social dilemmas are an under appreciated mechanism that can drive the evolution of corporate territorial ownership. When social dilemmas emerge, the costs associated with provisioning the public goods of information on resources or, perhaps, common defense create situations in which human foragers gain more by cooperating to recognize corporate ownership rules than they lose. Our results also indicate that societies who share a common cultural history are more
likely to recognize corporate ownership, and there is a spatial dynamic in which societies who live near each other are more likely to recognize corporate ownership as the number of near-by groups who recognize ownership increases. Our results have important implications for investigating the
coevolution of territorial ownership and the adoption of food production in the archaeological record.
Diversity is generally valued, although it sometimes contributes to difficult social situations, ... more Diversity is generally valued, although it sometimes contributes to difficult social situations, as is recognized in recent social science literature. Archaeology can provide insights into how diverse social situations play out over the long term. There are many kinds of diversities, and we propose representational diversity as a distinct category. Representational diversity specifically concerns how and whether differences are marked or masked materially. We investigate several archaeological sequences in the U.S. Southwest. Each began with the coming together of populations that created situations of unprecedented social diversity; some resulted in conflict, others in long-term stability. We trace how representational diversity changed through these sequences. Specifically, we review the transregional Kayenta migration to the southern Southwest and focus empirical analyses on regional processes in the Cibola region and on painted ceramics. Results show that, initially, representational diversity increased above and beyond that caused by the combination of previously separate traditions as people marked their differences. Subsequently, in some instances, the diversity was replaced by widespread homogeneity as the differences were masked and mitigated. Although the social causes and effects of diversity are many and varied, long-term stability and persistence is associated with tolerance of a range of diversities.
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under improving conditions (positive disturbance) groups with higher general intelligence perform better. However, when conditions deteriorate (negative disturbance) groups with high competency in both general and social intelligence are less likely to deplete resources and harvest more. Thus, we propose that a functional diversity of cognitive abilities improves how effectively social groups govern common pool resources, especially when conditions deteriorate and groups need to re-evaluate and change their behaviors.
hunter-gatherer territorial dynamics. We develop and evaluate three hypotheses for the effects of corporate territorial ownership and the storage of food on the territory size of hunter-gatherer societies. We seek to initiate a more nuanced understanding of how social and technological organization cause and constrain the size of hunter-gatherer territories, in addition to the factors of population size and the productivity of ecosystems documented among primates and mammals in general. Our analysis suggests that the storage of food fundamentally alters population-territory size dynamics in hunter-gatherer societies. When societies store food, territory size is a sub-linear function of population. When societies do not store food, the function is approximately linear. The sub-linear scaling of population and territory size indicates that when societies store food, the social units that comprise ethno-linguistic groups produce
more food per unit of area and share ever more over-lapping
subsistence ranges in response to population growth. This non-linear population-territory size relationship signals that coevolutionary processes initiated by different ways of constructing a niche generate diversity in hunter-gatherer societies. We speculate that the storage of food, initiated to cope with the short-term risk of a short-fall of food, has long-term consequences on the trajectory of hunter-gatherer
evolution in general.
Ecological models are a fundamental tool that archaeologists use to clarify our thinking about the processes that generate the archaeological record. Typically, arguments reasoned from a single model are bolstered by observing the consistency of ethnographic data with the argument. This is often referred to as model validation, and establishes that an argument is reasonable. In this paper, we move beyond validation by comparing the consistency of two arguments reasoned from different models that may explain corporate territorial ownership with data from a large sample of ethnographic cases. Our results suggest that social dilemmas are an under appreciated mechanism that can drive the evolution of corporate territorial ownership. When social dilemmas emerge, the costs associated with provisioning the public goods of information on resources or, perhaps, common defense create situations in which human foragers gain more by cooperating to recognize corporate ownership rules than they lose. Our results also indicate that societies who share a common cultural history are more
likely to recognize corporate ownership, and there is a spatial dynamic in which societies who live near each other are more likely to recognize corporate ownership as the number of near-by groups who recognize ownership increases. Our results have important implications for investigating the
coevolution of territorial ownership and the adoption of food production in the archaeological record.
social science literature. Archaeology can provide insights into how diverse social situations play out over the long term.
There are many kinds of diversities, and we propose representational diversity as a distinct category. Representational
diversity specifically concerns how and whether differences are marked or masked materially. We investigate several archaeological
sequences in the U.S. Southwest. Each began with the coming together of populations that created situations of
unprecedented social diversity; some resulted in conflict, others in long-term stability. We trace how representational
diversity changed through these sequences. Specifically, we review the transregional Kayenta migration to the southern
Southwest and focus empirical analyses on regional processes in the Cibola region and on painted ceramics. Results show
that, initially, representational diversity increased above and beyond that caused by the combination of previously separate
traditions as people marked their differences. Subsequently, in some instances, the diversity was replaced by widespread
homogeneity as the differences were masked and mitigated. Although the social causes and effects of diversity are many
and varied, long-term stability and persistence is associated with tolerance of a range of diversities.
under improving conditions (positive disturbance) groups with higher general intelligence perform better. However, when conditions deteriorate (negative disturbance) groups with high competency in both general and social intelligence are less likely to deplete resources and harvest more. Thus, we propose that a functional diversity of cognitive abilities improves how effectively social groups govern common pool resources, especially when conditions deteriorate and groups need to re-evaluate and change their behaviors.
hunter-gatherer territorial dynamics. We develop and evaluate three hypotheses for the effects of corporate territorial ownership and the storage of food on the territory size of hunter-gatherer societies. We seek to initiate a more nuanced understanding of how social and technological organization cause and constrain the size of hunter-gatherer territories, in addition to the factors of population size and the productivity of ecosystems documented among primates and mammals in general. Our analysis suggests that the storage of food fundamentally alters population-territory size dynamics in hunter-gatherer societies. When societies store food, territory size is a sub-linear function of population. When societies do not store food, the function is approximately linear. The sub-linear scaling of population and territory size indicates that when societies store food, the social units that comprise ethno-linguistic groups produce
more food per unit of area and share ever more over-lapping
subsistence ranges in response to population growth. This non-linear population-territory size relationship signals that coevolutionary processes initiated by different ways of constructing a niche generate diversity in hunter-gatherer societies. We speculate that the storage of food, initiated to cope with the short-term risk of a short-fall of food, has long-term consequences on the trajectory of hunter-gatherer
evolution in general.
Ecological models are a fundamental tool that archaeologists use to clarify our thinking about the processes that generate the archaeological record. Typically, arguments reasoned from a single model are bolstered by observing the consistency of ethnographic data with the argument. This is often referred to as model validation, and establishes that an argument is reasonable. In this paper, we move beyond validation by comparing the consistency of two arguments reasoned from different models that may explain corporate territorial ownership with data from a large sample of ethnographic cases. Our results suggest that social dilemmas are an under appreciated mechanism that can drive the evolution of corporate territorial ownership. When social dilemmas emerge, the costs associated with provisioning the public goods of information on resources or, perhaps, common defense create situations in which human foragers gain more by cooperating to recognize corporate ownership rules than they lose. Our results also indicate that societies who share a common cultural history are more
likely to recognize corporate ownership, and there is a spatial dynamic in which societies who live near each other are more likely to recognize corporate ownership as the number of near-by groups who recognize ownership increases. Our results have important implications for investigating the
coevolution of territorial ownership and the adoption of food production in the archaeological record.
social science literature. Archaeology can provide insights into how diverse social situations play out over the long term.
There are many kinds of diversities, and we propose representational diversity as a distinct category. Representational
diversity specifically concerns how and whether differences are marked or masked materially. We investigate several archaeological
sequences in the U.S. Southwest. Each began with the coming together of populations that created situations of
unprecedented social diversity; some resulted in conflict, others in long-term stability. We trace how representational
diversity changed through these sequences. Specifically, we review the transregional Kayenta migration to the southern
Southwest and focus empirical analyses on regional processes in the Cibola region and on painted ceramics. Results show
that, initially, representational diversity increased above and beyond that caused by the combination of previously separate
traditions as people marked their differences. Subsequently, in some instances, the diversity was replaced by widespread
homogeneity as the differences were masked and mitigated. Although the social causes and effects of diversity are many
and varied, long-term stability and persistence is associated with tolerance of a range of diversities.