Summed Probability Distributions Research Articles

Climate Change and Indigenous Subsistence in the Thompson River Watershed (British Columbia) in the Late Holocene

ABSTRACT The Indigenous peoples of the Thompson River watershed on the northern Columbia Plateau traditionally subsisted in winter on dried salmon, dried roots and berries from upland meadows, and game. A summed probability distribution (SPDF) based on 54 radiocarbon ages from twenty-eight winter villages and summer fishing camps along that river exhibits volatile activity in anti-phase with an SPDF derived from 77 radiocarbon ages from twenty-six sites in the neighbouring uplands in the 2500–500 cal BP interval. Activity levels on the riverbanks decline after ∼2000 cal BP, increase rapidly from ∼1600 cal BP to ∼1350 cal BP, fall dramatically in the next century, then rise again after ∼700 cal BP, echoing patterns at other upriver fisheries on the northern Columbia plateau. Periods of increased activity on the Thompson riverbank are linked to robust runs of sockeye salmon, prompted by cooler/wetter phases of regional climate, and marked by higher lake levels, glacial advances, and increased rates of coastal upwelling in the northeast Pacific. Less reliable salmon harvests in the intervening periods are indicated by increases in activity in the uplands, with a concomitant greater reliance on roots and game in the local diet.

馬韓·百濟·韓濊 권역의 인구변동

This study aims to investigate population dynamics in the Mahan, Baekje, and Ye regions. Settlement sites excavated in the Seoul-Gyeonggi, Yeongseo, Hoseo, and Honam regions, along with associated radiocarbon dates (2000-1300 BP), were compiled to assess their temporal and spatial distribution. Following adjustments to ensure the representativeness of the radiocarbon dates, trends in population growth and decline over time were analyzed using summed probability distributions of radiocarbon dates. Overall, a gradual increase in the density of radiocarbon dates was observed, peaking around 1750-1550 calBP before declining. This decline was attributed, to some extent, to changes in residential patterns and significant sampling biases. Regional analyses revealed variations in the timing and magnitude of population changes, with an earlier decline observed in the Yeongseo region around 1700 calBP compared to other regions, while the Hoseo and Honam regions experienced significant increases from around 1750 calBP before declining after 1550 calBP. Spatial distributions examined through kernel density analysis corresponded to these findings. While interpreting these changes based solely on the analysis presented herein may be insufficient, considering previous discussions, it is suggested that changes in trade networks and military tensions may have been important factors contributing to the early population decline in the Yeongseo region and northern Gyeonggi Province. Additionally, further investigation is required to provide a more convincing explanation for the significant population increase in the Mahan region during the period of Baekje's expansion.

Early Holocene inundation of Doggerland and its impact on hunter-gatherers: An inundation model and dates-as-data approach

Sea-level rise was a key factor changing environments during the Early Holocene in Northwest Europe. It affected Mesolithic hunter-gatherer communities by inundating large areas in the current North Sea, commonly referred to as Doggerland. In this paper we present novel inundation models for the southern North Sea providing visualisations of lateral inundation driven by sea-level rise and relate it to frequency analysis of radiocarbon dates from archaeological sites. These improve on previous studies that relied on bathymetric data, which includes post-inundation overprints of Holocene sedimentation and erosion, and thus significantly underestimates the timing of inundation in some areas.We constructed a paleoDEM (a composite elevation grid of the top of the Pleistocene) for the eastern part of the southern North Sea; and sea level surfaces that combine relative sea-level curves from glacio-isostatic adjustment models optimised for Britain and southern Scandinavia respectively. We corrected our paleoDEMs for tectonic background basin subsidence, and in the inundation modelling account for pre-compaction elevation of peat in coastal areas. We evaluated the impact of these model components on our results and describe the possible inundation history of Doggerland. We suggest earlier inundation than predicted by previous models, showing significant area loss around 10.5–10 ka cal BP.Palaeogeographic changes are compared with archaeological radiocarbon data using a dates-as-data approach. Composite Kernel Density Estimate and permutation tested Summed Probability Distributions are used as a proxy for the visibility, nature and intensity of human activity. Results indicate key periods of growth and decline recorded in the dataset, as well as regional differences in growth rate, some correlating with inundation phases. Chiefly, we find elevated growth rates around 10.5–10 ka in northwest Germany and the Netherlands, contemporaneous with the abovementioned phase of extensive area loss, and moreover, with changes in culture and practices on Early Mesolithic sites.However, the spatiotemporal distribution of archaeological data is significantly influenced by accessibility and preservation of sediments of a certain age. We discuss the importance of inundation modelling and sediment data in understanding how landscape taphonomy affects archaeological patterning, especially in dates-as-data approaches.

Statistical mechanical characterization of billiard systems

Area-preserving maps play an important role in diverse fields as they are widely used for modeling complex systems. In addition, these maps provide rich observations by presenting stable orbits and chaotic behavior separately or together in the phase space depending on the control parameter. In recent years, several studies on these maps, drawing inspiration from the phase space dynamics, have shown that nonextensive statistical mechanics provides appropriate instruments to characterize these systems. In this study, we perform a rigorous numerical analysis to delve into the statistical mechanical properties of a billiard system. Our primary goal is to confirm the presence of a q-Gaussian distribution, with an estimated q value of approximately 1.935. We accomplish this by examining the probability distribution of the cumulative sum of system iterates, focusing specifically on initial conditions within the stability islands. Our findings align seamlessly with the latest research in this field. Furthermore, we show that a multi-component probability distribution containing both Gaussian and q-Gaussians describes the entire system for some parameter regions where the phase space consists of stability islands together with the chaotic sea.

What burned the forest? Wildfires, climate change and human activity in the Mesolithic – Neolithic transition in SE Iberian Peninsula

Climate variability such as higher or lower temperatures, changing precipitation patterns, shifts in plant communities and other climate-related changes have particularly affected areas with Mediterranean-type climates. A multi-proxy analysis including pollen, sedimentary charcoal, mineralogy and Summed Probability Distributions (SPD) of archaeological 14C dates, allowed the reconstruction of landscape change, geomorphological evolution and fire history at the Laguna de Villena, in the southeastern Iberian Peninsula, during the Mesolithic-Neolithic transition. The Villena paleolake was sensitive to Early Holocene and Middle Holocene regional climatic variability that included several arid phases (around 8.2 ka cal BP, 6.8 ka cal BP and 5.9 ka cal BP) according to geochemical and pollen data. During this period, landscape dynamics show the degradation of oak forests and expansion of pyrophytic pine forests and shrublands, as well as open spaces predominated by grasses. The charcoal record shows a decreasing trend of biomass burned from 8.5 ka cal BP onwards, although fire peaks occurred recurrently during the Early and Middle Holocene. The most intense phase of fire activity was experienced in the last millennia of the Early Holocene, with five fire episodes from 9.1 to 8.4 ka cal BP, coinciding with a phase of higher archaeological evidence in the area. A decrease in archaeological evidence coincides with a gap in fire episodes during the Early Holocene-Middle Holocene transition, suggesting an effect of the abrupt 8.2 ka cal BP event on human activity and on landscape dynamics. After 8.0 ka cal BP, lowerer biomass burned is explained by the configuration of a more open landscape due to the combination of climate (increasing aridity) and increasing human activities in the region. The mineralogical and palynological data highlighted the interaction between human activities, climate and fire dynamics. The sedimentary charcoal record evidenced how most of the fire peaks did not occur in the context of dry episodes, as often assumed, deriving on an anthropogenic explanation related to Early and Late Mesolithic burning practices during a phase of higher archaeological evidence in the Villena paleolake surroundings. Afterwards, combined agropastoral activities from the Early Neolithic onwards and increasing aridity during the Middle Holocene maintained the forest clearances, in the context of fire episodes characterised by decreased biomass burned. This study shows how Middle Holocene palaeoecological records reflect complex histories blending climate and anthropogenic processes that derived in major landscape changes explaining the origin of current landscapes.

Settlement and conflict distribution responses to paleoclimate variation on the Columbia Plateau

Semi-subterranean house occupation in the southern Columbia Plateau of Western North America was episodic over the latter half of the Holocene. Several analyses of radiocarbon chronologies for house features have emphasized environmental change as a primary catalyst of shifts in subsistence strategies and house settlement. Our analysis incorporates summed probability distributions of radiocarbon dates for house occupations, climatic conditions, and evidence of conflict to assess the relationship among the three variables. Climate change is outlined using previously published proxy data. Results of our analysis indicate that climate had a strong influence on the settlement systems of the southern Columbia Plateau. Along with the direct influence of climate on resource availability, conflict became more frequent when house communities became larger. Developing a greater understanding of the cause and effect, and timing of environmental and social changes will ultimately require more robust datasets for house occupations, simulations of demographic trajectories, and higher resolution temporal and spatial models of climate change on the Columbia Plateau.

Parsing prehistoric patterns: Prospects and limitations of a big radiocarbon dataset for understanding the impact of climate on Late Palaeolithic and Mesolithic populations in northwest Europe (16–7.5 ka calBP)

Hunter-gatherer populations in northwest Europe were variably affected by Late Glacial and Early Holocene climate fluctuations and their effects on sea level and the environment. We investigate the impact of these fluctuations with a dates-as-data approach to a large radiocarbon dataset. Radiocarbon dates are used as a proxy for past human activity, the intensity, nature and archaeological visibility of which will indirectly influence date density. The significance of changes is explored using Kernel Density Estimates and model tested Summed Probability Distributions. Whereas previous studies have focused on smaller highly curated datasets to minimise research and preservation biases, our more inclusive approach maximises sample size, which is essential for these methods to reliably reflect underlying patterns. To deal with biases, we test subsets of the dataset that are potentially affected by differences in formation processes.The summed radiocarbon dataset follows the general fluctuations of climate conditions, showing increased activity in temperate periods and decreased activity during cold phases. Our results indicate significant periods of interest where the data deviates positively or negatively from our models. Notably we observe the impact of the Younger Dryas, Preboreal Oscillation and the 8.2 ka event on the density of hunter-gatherer activity. Additionally we see peaks in activity in our dataset during the Early and Late Boreal. Permutation testing of different regions in the research area shows these patterns are geographically differentiated.Our exploration of biasing factors indicates that we should be careful to interpret the abovementioned patterns, as different sampling processes and national policies may lie at the basis of several patterns. Furthermore, calibration artefacts may also cause issues at key parts of the timeline. Dates-as-data approaches require an understanding of the archaeology, the timing of external events, the impact of the calibration curve and how biases inherent to the dataset and research area may have influenced the formation of patterns in the result.

Early postglacial hunter-gatherers show environmentally driven “false logistic” growth in a low productivity environment

Studies that employ probability distributions of radiocarbon dates to study past population size often use exponential increase in radiocarbon dates with time as a standard of comparison for detecting population fluctuations. We show that in the case of early postglacial interior Scandinavia, however, the summed probability distribution of radiocarbon dates has best fit with a S-shaped logistic growth curve. Despite the logistic growth model having solid grounding in ecological theory, we further argue that what our data indicate is not logistic growth in the population ecological sense but “false logistic” growth that mainly follows from climatic and environmental forcing. In the initial postglacial phase, 9500–7500 BCE, human settlement was located almost exclusively along the Scandinavian Atlantic coast and the use of the mountainous interior remained low. Thereafter the formation of separate inland adaptations resulted in population growth in tandem with increasing climatic warming and environmental productivity. Some millennia later, when environmental productivity started to decrease after the Holocene Thermal Maximum, hunter-gatherer population size in interior Scandinavia reached a plateau that lasted at least 2000 years. Lowering productivity prevented any population growth that would be detectable in the available archaeological record.

SINE QUA NON: INFERRING KODJADERMEN-GUMELNIȚA-KARANOVO VI POPULATION DYNAMICS FROM AGGREGATED PROBABILITY DISTRIBUTIONS OF RADIOCARBON DATES

ABSTRACTPast human population dynamics play a key role in integrated models of understanding socio-ecological change over time. However, little analysis on this issue has been carried out for the prehistoric societies in the Lower Danube and Eastern Balkans area. Here, we use summed probability distributions of radiocarbon dates to investigate potential regional and local variation population dynamics. Our study adopts a formal model-testing approach to the fifth millennium BC archaeological radiocarbon record, performing a region-wide, comparative analysis of the demographic trajectories of the area along lower Danube River. We follow the current framework of theoretical models of population growth and perform global and regional significance and spatial permutation tests on the data. Specifically, we investigate whether populations on both sides of the Danube follow a logistic pattern of steady growth, followed by a major decline over time. Finally, our analysis of local-scale growth investigates whether considerable heterogeneity or homogeneity within the region may be observed over the time span considered here. The results show both similarities and differences in the population trends across the area. Our findings are showcased in relation to the cultural characteristics of the region’s 5th millennium BC societies, and future research directions are also suggested.

한성기 백제 왕성의 운영 시기와 변화 양상에 관한 연구

This study explores the chronological and functional relationship between the Mongchontoseong and Pungnabtoseong, the two royal capital cities of Hanseong Baekje State (300 AD-475 AD). As a result of accumulation of excavation data, it is possible to examine the archaeological aspects of regarding the management of the two capital cities in Baekje. According to the summed probability distribution of radiocarbon dates and pottery type analysis, an apex period of Pungnabtoseong was preceded to Mongchontoseong. Moreover, based upon the Bayesian modeling of radiocarbon dates and settlement patterns, the usage period of the capital cities can be divided into three. In Phase 1, Pungnabtoseong was firstly occupied and residential facilities appeared. In Phase 2, ritual facilities and urban infrastructure were viably installed in Pungnabtoseong. During Phase 3, as Mongchontoseong began to expand its scale, the function of Pungnabtoseong changed. While ritual and storage facilities were mostl-y found in Pungnabtoseong, residential, ritual, storage facilities and other infrastructure were comprehensively identified in Mongchontoseong. The spatial-temporal change in two capital cities presents the change in urban management of capitals during the early Baekje state. Before the construction of Mongchontoseong, Pungnabtoseong was used as a singular capital city. However, Mongchontoseong concurrently took a role of the urban center under different functions with Pungnabtoseong.

Past maize consumption correlates with population change in Central Western Argentina

This paper explores the relationships between population change and human diet after the adoption of domesticated resources in northwest Mendoza, a subregion of central western Argentina (CWA). To estimate population, we used summed probability distributions of radiocarbon ages (RC-SPD). We used carbon and nitrogen stable isotope values (ẟ13Cco, ẟ13Cca, and ẟ15N) obtained on human bone (collagen and carbonate) to reconstruct human diet. The population trend of late Pleistocene-Holocene hunter-gatherers changed its trajectory ca. 2300 cal years BP coincident with the adoption of domesticates. After this date, a significant increase in human population occurred. We observe population increases (“booms”) followed by notable drops (“busts”). Stable isotopes (ẟ13C) on human bone follow a similar trend, indicating an increased consumption of maize during the “boom” periods and a decreased consumption during the “bust” periods. Based on the association between estimated changes in human population and changes in human bone isotope values over the last 2300 cal years BP, we propose that levels of maize consumption emerge from human predator–prey and plant-herbivore interactions. The use of maize, thus, is not part of a social evolutionary stage, but, rather, an outcome of continuous social-ecological process in which maize use may increase or decrease over time.

Long-term demographic trends and spatio-temporal distribution of past human activity in Central Europe: Comparison of archaeological and palaeoecological proxies

Estimating past population dynamics has become a major research topic for archaeology, which uses several proxies for studying past demography. The Czech Republic represents a unique region with abundant digital archaeological and palynological datasets comprising tens of thousands of records covering the whole Holocene. We used these datasets to quantify long-term demographic trends and to delimit past human activity in space and time. Our results, based on large data from both disciplines, are one of the first quantitative results covering the whole Czech Republic. Through summed probability distributions of radiocarbon dates and spatio-temporal modelling of human activity based on archaeological sites, we identified four major demographic events and processes between 10,000 BCE and 1000 CE – the beginning of the Neolithic at 5400 BCE, the Eneolithic/Bronze Age transition in the 3rd millennium BCE, Bronze Age expansion after 1500 BCE, and mediaeval expansion after 500 CE. We identified two settlement cores in the lowlands, with additional inner and outer peripheries with different demographic histories. Our study clearly shows that prehistoric and early historic population dynamics were not a homogenised process and were regionalized according to local environmental and social conditions. The comparison of archaeological results with pollen-based vegetation proxies also showed regional aspects in human-vegetation interactions. Agro-pastoral communities dwelling in the lowlands mostly influenced the openness of the landscape, used for fields and pastures, whereas contemporary communities with a similar economic mode residing in a different region are more visible in pollen records through species and structural changes in woodlands. The agro-pastoral subsistence strategy did not start everywhere with the onset of the Neolithic: in some regions it failed after several centuries, in others, the foraging lifestyle persisted significantly longer, and farming became a major economic strategy much later. Our study shows that archaeological site-based and 14C-based demographic proxies cannot be utilized for all periods and regions due to several limitations. Only the combination of different quantitative and qualitative archaeological proxies for population does reveal important details.

From Neolithic Boom-and-Bust to Iron Age Peak and Decline: Population and Settlement Dynamics in Southern Sweden Inferred from Summed Radiocarbon Dates

This article presents 6637 radiocarbon dates from archaeological sites in southernmost Sweden, from 9000 cal bc to the present. Based on summed probability distributions (SPDs) of the calibrated radiocarbon dates, the authors consider long-term trends in settlement and human population. Most dates are from the fertile and densely populated plains of south-western Scania, but coastal lowlands and forested uplands are also represented, allowing for a discussion of the relationship between central and peripheral areas. The authors distinguish between different types of archaeological contexts and features and between different types of dated material, so as to better understand the processes behind population and settlement change. They highlight three periods and phenomena revealed by the SPDs: a strong population increase at the onset of the Neolithic (4000–3700 cal bc), followed by a sharp decline; a steady and long-lasting expansion from the Early Bronze Age to the Roman Iron Age (1500 cal bc–cal ad 200); and a decrease in the Nordic Late Iron Age (seventh century ad), particularly in recently colonized upland areas. The SPDs presented provide a new framework for archaeology in southern Sweden and offer an empirical basis for discussion of long-term trends in settlement and population development.

New Edgeworth-type expansions with finite sample guarantees

We establish higher-order nonasymptotic expansions for a difference between probability distributions of sums of i.i.d. random vectors in a Euclidean space. The derived bounds are uniform over two classes of sets: the set of all Euclidean balls and the set of all half-spaces. These results allow to account for an impact of higher-order moments or cumulants of the considered distributions; the obtained error terms depend on a sample size and a dimension explicitly. The new inequalities outperform accuracy of the normal approximation in existing Berry-Esseen inequalities under very general conditions. Under some symmetry assumptions on the probability distribution of random summands, the obtained results are optimal in terms of the ratio between the dimension and the sample size. The new technique which we developed for establishing nonasymptotic higher-order expansions can be interesting by itself. Using the new higher-order inequalities, we study accuracy of the nonparametric bootstrap approximation and propose a bootstrap score test under possible model misspecification. The results of the paper also include explicit error bounds for general elliptic confidence regions for an expected value of the random summands, and optimality of the Gaussian anti-concentration inequality over the set of all Euclidean balls.

Ecosystem productivity affected the spatiotemporal disappearance of Neanderthals in Iberia

What role did fluctuations play in biomass availability for secondary consumers in the disappearance of Neanderthals and the survival of modern humans? To answer this, we quantify the effects of stadial and interstadial conditions on ecosystem productivity and human spatiotemporal distribution patterns during the Middle to Upper Palaeolithic transition (50,000–30,000 calibrated years before the present) in Iberia. First, we used summed probability distribution, optimal linear estimation and Bayesian age modelling to reconstruct an updated timescale for the transition. Next, we executed a generalized dynamic vegetation model to estimate the net primary productivity. Finally, we developed a macroecological model validated with present-day observations to calculate herbivore abundance. The results indicate that, in the Eurosiberian region, the disappearance of Neanderthal groups was contemporaneous with a significant decrease in the available biomass for secondary consumers, and the arrival of the first Homo sapiens populations coincided with an increase in herbivore carrying capacity. During stadials, the Mediterranean region had the most stable conditions and the highest biomass of medium and medium–large herbivores. These outcomes support an ecological cause for the hiatus between the Mousterian and Aurignacian technocomplexes in Northern Iberia and the longer persistence of Neanderthals in southern latitudes.

Tracing Maize History in Northern Iroquoia Through Radiocarbon Date Summed Probability Distributions

Abstract The evolution of maize as an organism, its spread as an agricultural crop, and the evolution of Native American maize-based agricultural systems are topics of research throughout the Western Hemisphere. Maize was adopted in Northern Iroquoia, comprising portions of present-day New York, Ontario, and Québec by 300 BC. By the fourteenth-century AD, maize accounted for >50 to >70% of ancestral Iroquoian diets. Was this major commitment to maize agriculture a gradual incremental evolution, or was there a rapid increase in commitment to maize-based agriculture around AD 1000 as traditional archaeological narratives suggest? Summed probability distributions of direct radiocarbon dates on maize macrobotanical remains and cooking residues containing maize phytoliths combined with maize macrobotanical maize densities at sites and previously published stable isotope values on human bone collagen used with Bayesian dietary mixing models and cooking residues show an initial increase in maize use at AD 1200–1250 and a subsequent increase at AD 1400–1450. These results indicate maize history in Northern Iroquoia followed an exponential growth curve, consistent with Rindos’ (1984) model of agricultural evolution.

Two thousand years of Landscape—Human interactions at a coastal peninsula in Norway revealed through pollen analysis, shoreline reconstruction, and radiocarbon dates from archaeological sites

Human impact on long-term vegetation and biodiversity changes is often discussed on a general level, connecting palynological data to archaeological time periods. In the present paper we present environmental change during the last 2,400 years on a coastal peninsula in Norway using pollen data from three sites: one lake and two bogs, in addition to 621 radiocarbon dates and in-context pollen samples from archaeological sites. Locally, a close relationship between palynological richness reflecting high landscape, habitat and floristic diversity, and the summed probability distribution of radiocarbon dates was found. During the settlement period 400 BCE–550 CE, concordant with maximum number of dates from archaeological contexts, a mosaic landscape containing infields and outfields developed. Cereals were cultivated and animals were grazing in heathlands that could provide both summer grazing and winter fodder. Additionally, seashores and wetlands were used for grazing. Settlement recession from 350 CE and abandonment following the 536 CE climate event, resulted in vegetation successions toward reforestation, abandonment of arable fields, and marshes turning into ombrotrophic peat. At the same time the distance to the sea, and to species rich shoreline meadows, continued to increase due to continuous postglacial land uplift in a flat landscape. A new increase in the summed probability distribution 900–1250 CE, is reflected in expansion of outfield pastures, heathlands in particular, a management that continued up into modern time. The local development is supported by the results on a regional scale, indicating overall climatic and social causes for observed vegetation changes. Both palynological richness and pollen-based landcover reconstructions indicate reforestation and less habitat diversity in the sixth century. On a regional scale, reforestation in the fifteenth century following the late medieval crises, is more pronounced than on the local scale, although both reflect exploitation of outfield resources.

Funerary Diversity and Cultural Continuity: The British Beaker Phenomenon Beyond the Stereotype

The Beaker phenomenon in Britain is typically represented by a particular form of pottery and its inclusion in graves with flexed or crouched inhumations referred to as Beaker burials. Analysis of the full range of burial evidence, however, reveals a high degree of variability in funerary rites including cremation and skeletal disarticulation. Summed probability distribution analysis of radiocarbon dates provides evidence for continuity of these other, atypical rites from the pre-Beaker Late Neolithic (c.3000–2450 calbc) through the Chalcolithic (c.2450–2200 calbc) and into the Early Bronze Age (afterc.2200 calbc). Regional diversity is apparent in Beaker period funerary treatments and grave good provision between these typical and atypical rites, as is differential selection of rites on the basis of age and biological sex. This evidence for within and between community funerary diversity has implications for understanding the large-scale processes of cultural and genomic transformation across this period of major transition in British prehistory.

The development and disintegration of a Classic Maya center and its climate context

Research in Southern Belize has produced a 1000-year record of coupled human and environmental relationships at the ancient Maya city Uxbenká. Located at the southeastern margin of the Maya Lowlands, this region has excellent agricultural land and some of the highest rainfall in the Maya region. Uxbenká was the founding political center in southern Belize after 100 BCE. After 850 years, Uxbenká experienced a long geopolitical disintegration ending in depopulation as part of broad regional collapse. We use kernel density and summed probability distributions of 167 high-precision AMS 14C dates to reconstruct relative changes in population and investments in the built environment throughout the growth and decline of the polity. Those data are compared to an annually resolved speleothem paleoclimate record from Yok Balum cave, located less than 3 km from Uxbenká’s civic ceremonial core. With no Classic Period wetland fields or evidence for large-scale landscape investments in agricultural intensification, food production would have been rainfall dependent as was water availability for household use. Using a 30 m SRTM DEM, we compute flow accumulation and the upvalley extents of river networks while varying the input precipitation to reflect hypothesized changes in paleorainfall over time. Our data suggest that Uxbenká experienced rapid growth following a severe drought at 200 CE, as well as cycles of growth and contraction until just after 750 CE. We find that geopolitical disintegration in southern Belize was already underway when a severe drought began at 830 CE. That six-decade drought likely contributed to the abandonment of Uxbenká and limited geopolitical reorganization.

Divergent population dynamics in the middle to late Holocene lower Fraser valley and mid-Fraser canyon, British Columbia

Modelling in demographic ecology offers insights into population stability and instability in village societies. In this study we explore the hypothesis that among storage dependent fisher-hunter-gatherers, access to high resource diversity favors reduced demographic volatility over time. To better understand this relationship, we generate summed probability distributions (SPDs) from legacy radiocarbon records to model the population histories of Middle to late Holocene groups residing in the Mid-Fraser Canyon and the Lower Fraser Valley, British Columbia. Our analysis indicates that Lower Fraser populations (with high subsistence resource diversity) were highly stable after 4000 years ago. In contrast, Mid-Fraser populations (with lower subsistence resource diversity) were very low 2000–4000 cal. BP, peaked at high densities by ca. 1200–1300 cal. BP, and were again low until the final centuries before first contacts with Europeans. We argue that climate related impacts on anadromous fish resources likely affected Mid-Fraser populations to a more substantial degree than those of the Lower Fraser. These results offer wider implications concerning demographic volatility and its effects on cultural stability and social change. Our study offers a means by which legacy radiocarbon data may be studied using a permutation-based statistical inference of SPDs.