Influential individuals can promote prosocial practices in heterogeneous societies: a mathematical and agent-based model.

In this paper, we examine how different governance types impact prosocial behaviors in a heterogenous society. We construct a general theoretical framework to examine a game-theoretic model to assess the ease of achieving a cooperative outcome. We then build a dynamic agent-based model to examine three distinct governance types in a heterogenous population: monitoring one's neighbors, despotic leadership, and influencing one's neighbors to adapt strategies that lead to better fitness.

Wealth inequality in the prehispanic northern US Southwest: from Malthus to Tyche.

Persistent differences in wealth and power among prehispanic Pueblo societies are visible from the late AD 800s through the late 1200s, after which large portions of the northern US Southwest were depopulated. In this paper we measure these differences in wealth using Gini coefficients based on house size, and show that high Ginis (large wealth differences) are positively related to persistence in settlements and inversely related to an annual measure of the size of the unoccupied dry-farming niche. We argue that wealth inequality in this record is due first to processes inherent in village life which have internally different distributions of the most productive maize fields, exacerbated by the dynamics of systems of balanced reciprocity; and second to decreasing ability to escape village life owing to shrinking availability of unoccupied places within the maize dry-farming niche as villages get enmeshed in regional systems of tribute or taxation.

Drought assessment has been outpaced by climate change: empirical arguments for a paradigm shift.

Despite the acceleration of climate change, erroneous assumptions of climate stationarity are still inculcated in the management of water resources in the United States (US). The US system for drought detection, which triggers billions of dollars in emergency resources, adheres to this assumption with preference towards 60-year (or longer) record lengths for drought characterization. Using observed data from 1,934 Global Historical Climate Network (GHCN) sites across the US, we show that conclusions based on long climate records can substantially bias assessment of drought severity.

Earliest evidence for human use of tobacco in the Pleistocene Americas.

Current archaeological research on cultigens emphasizes the protracted and intimate human interactions with wild species that defined paths to domestication and, with certain plants, profoundly impacted humanity. Tobacco arguably has had more impact on global patterns in history than any other psychoactive substance, but how deep its cultural ties extend has been widely debated. Excavations at the Wishbone site, directed at the hearth-side activities of the early inhabitants of North America's desert west, have uncovered evidence for human tobacco use approximately 12,300 years ago, 9,000 years earlier than previously documented.

Loss of resilience preceded transformations of pre-Hispanic Pueblo societies.

Climate extremes are thought to have triggered large-scale transformations of various ancient societies, but they rarely seem to be the sole cause. It has been hypothesized that slow internal developments often made societies less resilient over time, setting them up for collapse. Here, we provide quantitative evidence for this idea.

Survival of the Systems.

Since Darwin, individuals and more recently genes, have been the focus of evolutionary thinking. The idea that selection operates on nonreproducing, higher-level systems including ecosystems or societies, has met with scepticism. But research emphasising that natural selection can be based solely on differential persistence invites reconsideration of their evolution.

Dendrochronological dates confirm a Late Prehistoric population decline in the American Southwest derived from radiocarbon dates.

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.

Genomic history and ecology of the geographic spread of rice.

Rice (Oryza sativa) is one of the world's most important food crops, and is comprised largely of japonica and indica subspecies. Here, we reconstruct the history of rice dispersal in Asia using whole-genome sequences of more than 1,400 landraces, coupled with geographic, environmental, archaeobotanical and paleoclimate data. Originating around 9,000 yr ago in the Yangtze Valley, rice diversified into temperate and tropical japonica rice during a global cooling event about 4,200 yr ago.

Scale and information-processing thresholds in Holocene social evolution.

Throughout the Holocene, societies developed additional layers of administration and more information-rich instruments for managing and recording transactions and events as they grew in population and territory. Yet, while such increases seem inevitable, they are not. Here we use the Seshat database to investigate the development of hundreds of polities, from multiple continents, over thousands of years.

Future of the human climate niche.

All species have an environmental niche, and despite technological advances, humans are unlikely to be an exception. Here, we demonstrate that for millennia, human populations have resided in the same narrow part of the climatic envelope available on the globe, characterized by a major mode around ∼11 °C to 15 °C mean annual temperature (MAT). Supporting the fundamental nature of this temperature niche, current production of crops and livestock is largely limited to the same conditions, and the same optimum has been found for agricultural and nonagricultural economic output of countries through analyses of year-to-year variation.

Climate change stimulated agricultural innovation and exchange across Asia.

Ancient farmers experienced climate change at the local level through variations in the yields of their staple crops. However, archaeologists have had difficulty in determining where, when, and how changes in climate affected ancient farmers. We model how several key transitions in temperature affected the productivity of six grain crops across Eurasia.

Greater post-Neolithic wealth disparities in Eurasia than in North America and Mesoamerica.

How wealth is distributed among households provides insight into the fundamental characters of societies and the opportunities they afford for social mobility. However, economic inequality has been hard to study in ancient societies for which we do not have written records, which adds to the challenge of placing current wealth disparities into a long-term perspective. Although various archaeological proxies for wealth, such as burial goods or exotic or expensive-to-manufacture goods in household assemblages, have been proposed, the first is not clearly connected with households, and the second is confounded by abandonment mode and other factors.

Prehistoric mitochondrial DNA of domesticate animals supports a 13th century exodus from the northern US southwest.

The 13th century Puebloan depopulation of the Four Corners region of the US Southwest is an iconic episode in world prehistory. Studies of its causes, as well as its consequences, have a bearing not only on archaeological method and theory, but also social responses to climate change, the sociology of social movements, and contemporary patterns of cultural diversity. Previous research has debated the demographic scale, destinations, and impacts of Four Corners migrants.

Twenty-first century approaches to ancient problems: Climate and society.

By documenting how humans adapted to changes in their environment that are often much greater than those experienced in the instrumental record, archaeology provides our only deep-time laboratory for highlighting the circumstances under which humans managed or failed to find to adaptive solutions to changing climate, not just over a few generations but over the longue durée Patterning between climate-mediated environmental change and change in human societies has, however, been murky because of low spatial and temporal resolution in available datasets, and because of failure to model the effects of climate change on local resources important to human societies. In this paper we review recent advances in computational modeling that, in conjunction with improving data, address these limitations. These advances include network analysis, niche and species distribution modeling, and agent-based modeling.

Exploration and exploitation in the macrohistory of the pre-Hispanic Pueblo Southwest.

Cycles of demographic and organizational change are well documented in Neolithic societies, but the social and ecological processes underlying them are debated. Such periodicities are implicit in the "Pecos classification," a chronology for the pre-Hispanic U.S.

THE SOCIAL CONSEQUENCES OF CLIMATE CHANGE IN THE CENTRAL MESA VERDE REGION.

The consequences of climate change vary over space and time. Effective studies of human responses to climatically induced environmental change must therefore sample the environmental diversity experienced by specific societies. We reconstruct population histories from A.

Demographic and Social Dimensions of the Neolithic Revolution in Southwest Colorado.

Domesticated food production is widely acknowledged as a crucial innovation that led to significant transformations in human demography and social organization. Here, we address demographic and social dimensions of the Neolithic Revolution in the Mesa Verde region of Southwest Colorado. We first propose a new method of dating habitations to one of two phases of the Basketmaker III period (AD 600-725) using relative frequencies of vessel forms in pottery assemblages.

Ritual drinks in the pre-Hispanic US Southwest and Mexican Northwest.

Chemical analyses of organic residues in fragments of pottery from 18 sites in the US Southwest and Mexican Northwest reveal combinations of methylxanthines (caffeine, theobromine, and theophylline) indicative of stimulant drinks, probably concocted using either cacao or holly leaves and twigs. The results cover a time period from around A.D.

DNA analysis of ancient dogs of the Americas: identifying possible founding haplotypes and reconstructing population histories.

As dogs have traveled with humans to every continent, they can potentially serve as an excellent proxy when studying human migration history. Past genetic studies into the origins of Native American dogs have used portions of the hypervariable region (HVR) of mitochondrial DNA (mtDNA) to indicate that prior to European contact the dogs of Native Americans originated in Eurasia. In this study, we summarize past DNA studies of both humans and dogs to discuss their population histories in the Americas.

A 2,000-year reconstruction of the rain-fed maize agricultural niche in the US Southwest.

Humans experience, adapt to and influence climate at local scales. Paleoclimate research, however, tends to focus on continental, hemispheric or global scales, making it difficult for archaeologists and paleoecologists to study local effects. Here we introduce a method for high-frequency, local climate-field reconstruction from tree-rings.