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

2020 ◽  
Vol 376 (1816) ◽  
pp. 20190718 ◽  
Author(s):  
Erick Robinson ◽  
R. Kyle Bocinsky ◽  
Darcy Bird ◽  
Jacob Freeman ◽  
Robert L. Kelly
Keyword(s):  
Time Series ◽  
North America ◽  
Population Decline ◽  
American Southwest ◽  
Human Populations ◽  
Late Prehistoric ◽  
Population Declines ◽  
Sample Collection ◽  
Radiocarbon Dates ◽  
Radiocarbon Data

The northern American Southwest provides one of the most well-documented cases of human population growth and decline in the world. The geographic extent of this decline in North America is unknown owing to the lack of high-resolution palaeodemographic data from regions across and beyond the greater Southwest, where archaeological radiocarbon data are often the only available proxy for investigating these palaeodemographic processes. Radiocarbon time series across and beyond the greater Southwest suggest widespread population collapses from AD 1300 to 1600. However, radiocarbon data have potential biases caused by variable radiocarbon sample preservation, sample collection and the nonlinearity of the radiocarbon calibration curve. In order to be confident in the wider trends seen in radiocarbon time series across and beyond the greater Southwest, here we focus on regions that have multiple palaeodemographic proxies and compare those proxies to radiocarbon time series. We develop a new method for time series analysis and comparison between dendrochronological data and radiocarbon data. Results confirm a multiple proxy decline in human populations across the Upland US Southwest, Central Mesa Verde and Northern Rio Grande from AD 1300 to 1600. These results lend confidence to single proxy radiocarbon-based reconstructions of palaeodemography outside the Southwest that suggest post-AD 1300 population declines in many parts of North America. This article is part of the theme issue ‘Cross-disciplinary approaches to prehistoric demography’.

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

2020 ◽  
Author(s):  
Erick Robinson ◽  
R. Kyle Bocinsky ◽  
Darcy Bird ◽  
Jacob Freeman ◽  
Robert L. Kelly
Keyword(s):  
Time Series ◽  
Population Decline ◽  
American Southwest ◽  
Human Populations ◽  
Late Prehistoric ◽  
Population Declines ◽  
Sample Collection ◽  
Radiocarbon Dates ◽  
Anal Ysis ◽  
Radiocarbon Data

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 Amer- ica is unknown due to the lack of high-resolution palaeodemographic data from regions across and beyond the greater Southwest, where archaeological radiocarbon data is often the only avail- able proxy for investigating these palaeodemographic processes. Radiocarbon time series across and beyond the greater Southwest suggest widespread population collapses from AD 1300–1600. However, radiocarbon data have potential biases caused by variable radiocarbon sample preser- vation, sample collection, and the non-linearity of the radiocarbon calibration curve. In order to be confident in the wider trends seen in radiocarbon time series across and beyond the greater Southwest, here we focus on regions that have multiple palaeodemographic proxies and com- pare those proxies to radiocarbon time series. We develop a new method for time series anal- ysis and comparison between dendrochronological data and radiocarbon data. Results confirm a multiple proxy decline in human populations across the Upland US Southwest, Central Mesa Verde, and Northern Rio Grande from AD 1300–1600. These results lend confidence to single proxy radiocarbon-based reconstructions of paleodemography outside the Southwest that sug- gest post-AD 1300 population declines in many parts of North America.

Evaluating the Old Wood Problem in a Temperate Climate: A Fort Ancient Case Study

2014 ◽  
Vol 79 (04) ◽  
pp. 763-775 ◽  
Author(s):  
Robert A. Cook ◽  
Aaron R. Comstock
Keyword(s):  
North America ◽  
American Southwest ◽  
Wood Charcoal ◽  
Arid Climate ◽  
Temperate Climate ◽  
Radiocarbon Dates ◽  
Eastern Woodlands ◽  
Fort Ancient

Abstract Schiffer (1986) first identified the old wood problem for wood charcoal-based dates from archaeological contexts in the American Southwest. The potential for dates to be skewed toward excessively old calendar ages in this region has recently generated reticence in part of the archaeological community towards including wood charcoal dates in general. Some scholars have even begun to cleanse the radiocarbon databases of regions throughout North America, partly with this presumed limitation in mind. However, the issues that contribute to the old wood problem have not been closely examined outside the arid climate of the American Southwest, resulting in some studies excluding hundreds of radiocarbon dates. The present study fills that void by examining the radiocarbon record from four well-dated Fort Ancient sites in southwestern Ohio and southeastern Indiana. Specifically, we test whether or not there are significant differences between wood charcoal and non-wood charcoal assays. Our findings suggest that wood charcoal dates should not be excluded. We explore reasons for this difference in the Eastern Woodlands and propose an ideal dating regime.

scholarly journals Climate change, not human population growth, correlates with Late Quaternary megafauna declines in North America

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Mathew Stewart ◽  
W. Christopher Carleton ◽  
Huw S. Groucutt
Keyword(s):  
Climate Change ◽  
North America ◽  
North American ◽  
Human Population ◽  
Late Quaternary ◽  
Bayesian Regression ◽  
Population Declines ◽  
Radiocarbon Dates ◽  
Population Sizes ◽  
Do So

AbstractThe disappearance of many North American megafauna at the end of the Pleistocene is a contentious topic. While the proposed causes for megafaunal extinction are varied, most researchers fall into three broad camps emphasizing human overhunting, climate change, or some combination of the two. Understanding the cause of megafaunal extinctions requires the analysis of through-time relationships between climate change and megafauna and human population dynamics. To do so, many researchers have used summed probability density functions (SPDFs) as a proxy for through-time fluctuations in human and megafauna population sizes. SPDFs, however, conflate process variation with the chronological uncertainty inherent in radiocarbon dates. Recently, a new Bayesian regression technique was developed that overcomes this problem—Radiocarbon-dated Event-Count (REC) Modelling. Here we employ REC models to test whether declines in North American megafauna species could be best explained by climate changes, increases in human population densities, or both, using the largest available database of megafauna and human radiocarbon dates. Our results suggest that there is currently no evidence for a persistent through-time relationship between human and megafauna population levels in North America. There is, however, evidence that decreases in global temperature correlated with megafauna population declines.

scholarly journals Widespread population decline in South America correlates with mid-Holocene climate change

2018 ◽  
Author(s):  
Philip Riris ◽  
Manuel Arroyo-Kalin
Keyword(s):  
Climate Change ◽  
South America ◽  
Large Scale ◽  
Climatic Variability ◽  
Population Decline ◽  
Plant Management ◽  
Human Populations ◽  
Resource Base ◽  
Radiocarbon Dates ◽  
Middle Holocene

Quantifying the impacts of climate change on prehistoric demography is crucial for understanding the adaptive pathways taken by human populations. Archaeologists across South America have pointed to patterns of regional abandonment during the Middle Holocene (8200 to 4200 cal BP) as evidence of sensitivity to shifts in hydroclimate over this period. We develop a unified approach to investigate demography and climate in South America and aim to clarify the extent to which evidence of local anthropic responses can be generalised to large-scale trends. We achieve this by integrating archaeological radiocarbon data and palaeoclimatic time series to show that population decline occurred coeval with the transition to the initial mid-Holocene across South America. Through the analysis of radiocarbon dates with Monte Carlo methods, we find multiple, sustained phases of downturn associated to periods of high climatic variability. A likely driver of the duration and severity of demographic turnover is the frequency of exceptional climatic events, rather than the absolute magnitude of change. Unpredictable levels of tropical precipitation had sustained negative impacts on pre-Columbian populations lasting until at least 6000 cal BP, after which recovery is evident. Our results support the inference that a demographic regime shift in the second half of the Middle Holocene were coeval with cultural practices surrounding Neotropical plant management and early cultivation, possibly acting as buffers when the wild resource base was in flux.

scholarly journals Spatially explicit analysis sheds new light on the Pleistocene megafaunal extinction in North America

Paleobiology ◽  
2017 ◽  
Vol 43 (4) ◽  
pp. 642-655 ◽  
Author(s):  
Meaghan M. Emery-Wetherell ◽  
Brianna K. McHorse ◽  
Edward Byrd Davis
Keyword(s):  
North America ◽  
Great Lakes ◽  
Human Activity ◽  
Late Pleistocene ◽  
North American ◽  
Human Populations ◽  
Great Lakes Region ◽  
Radiocarbon Dates ◽  
The North ◽  
Primary Driver

AbstractThe late Pleistocene megafaunal extinctions may have been the first extinctions directly related to human activity, but in North America the close temporal proximity of human arrival and the Younger Dryas climate event has hindered efforts to identify the ultimate extinction cause. Previous work evaluating the roles of climate change and human activity in the North American megafaunal extinction has been stymied by a reliance on geographic binning, yielding contradictory results among researchers. We used a fine-scale geospatial approach in combination with 95 megafaunal last-appearance and 75 human first-appearance radiocarbon dates to evaluate the North American megafaunal extinction. We used kriging to create interpolated first- and last-appearance surfaces from calibrated radiocarbon dates in combination with their geographic autocorrelation. We found substantial evidence for overlap between megafaunal and human populations in many but not all areas, in some cases exceeding 3000 years of predicted overlap. We also found that overlap was highly regional: megafauna had last appearances in Alaska before humans first appeared, but did not have last appearances in the Great Lakes region until several thousand years after the first recorded human appearances. Overlap in the Great Lakes region exceeds uncertainty in radiocarbon measurements or methodological uncertainty and would be even greater with sampling-derived confidence intervals. The kriged maps of last megafaunal occurrence are consistent with climate as a primary driver in some areas, but we cannot eliminate human influence from all regions. The late Pleistocene megafaunal extinction was highly variable in timing and duration of human overlap across the continent, and future analyses should take these regional trends into account.

scholarly journals Climate change, not human population growth, correlates with late Quaternary megafauna declines in North America

2021 ◽  
Author(s):  
Mathew Stewart ◽  
Christopher Carleton ◽  
Huw Groucutt
Keyword(s):  
Climate Change ◽  
North America ◽  
North American ◽  
Human Population ◽  
Late Quaternary ◽  
Bayesian Regression ◽  
Human Populations ◽  
Population Densities ◽  
Radiocarbon Dates ◽  
The North

<p>The late Quaternary saw the extinction of a great number of the world’s megafauna (those animals >44 kg), an event unprecedented in 65 million-years of mammalian evolution. Extinctions were notably severe in North America where 37 genera (~80%) of megafauna disappeared by around the late Pleistocene/Holocene boundary (~11.7 thousand-years-ago, or ka). Scholars have typically attributed these extinctions to overhunting by rapidly expanding human populations (i.e., overkill), climate change, or some combination of the two. Testing human- and climate-driven extinctions hypotheses in North America, however, has proven difficult given the apparent concurrency of human arrival in the Americas—more specifically, the emergence of Clovis culture (~13.2–12.9 ka)—and terminal Pleistocene climate changes such as the abrupt warming of the Bølling-Allerød interstadial (B-A; ~14.7–12.9 ka) or near-glacial conditions of the Younger-Dryas stadial (YD; 12.9–11.7 ka). Testing these hypotheses will, therefore, require the analysis of through-time relationships between climate change and megafauna and human population dynamics. To do so, many researchers have used summed probability density functions (SPDFs) as a proxy for through-time fluctuations in human and megafauna population sizes. SPDFs, however, conflate process variation with the chronological uncertainty inherent in radiocarbon dates. Recently, a new Bayesian regression technique was developed that overcomes this problem—Radiocarbon-dated Event-Count (REC) modelling. Using the largest available dataset of megafauna and human radiocarbon dates, we employed REC models to test whether declines in North American megafauna species could be best explained by climate change (temperature), increases in human population densities, or both. On the one hand, we reasoned that if human overhunting drove megafauna extinctions, there would be a negative correlation between human and megafauna population densities. On the other hand, if climate change drove megafauna extinctions, there would be a correlation between our temperature proxy (i.e., the North Greenland Ice Core Project [NGRIP] δ<sup>18</sup>O record) and megafauna population densities. We found no correlation between our human and megafauna population proxies and, therefore, no support for simple models of overkill. While our findings do not preclude humans from having had an impact—for example, by interrupting megafauna subpopulation connectivity or performing a coup de grâce on already impoverished megafauna—they do suggest that growing populations of “big-game” hunters were not the primary driving force behind megafauna extinctions. We did, however, consistently find a significant, positive correlation between temperature and megafauna population densities. Put simply, decreases in temperature correlated with declines in North American megafauna. The timing of megafauna population declines and extinctions suggest that the unique conditions of the YD—i.e., abrupt cooling, increased seasonality and CO<sub>2</sub>, and major vegetation changes—played a key role in the North American megafauna extinction event.</p>

Alligator Mound: Geoarchaeological and Iconographical Interpretations of a Late Prehistoric Effigy Mound in Central Ohio, USA

2003 ◽  
Vol 13 (2) ◽  
pp. 147-167 ◽  
Author(s):  
Bradley T. Lepper ◽  
Tod A. Frolking
Keyword(s):  
North America ◽  
Late Woodland ◽  
Eastern North America ◽  
Late Prehistoric ◽  
Radiocarbon Dates ◽  
Archaeological Investigation ◽  
Fort Ancient ◽  
Effigy Mound

Alligator Mound is an animal effigy mound in central Ohio, USA. Since Ephraim Squier and Edwin Davis first recorded and mapped it in 1848, many have speculated regarding its age and meaning, but with remarkably little systematic archaeological investigation. Many scholars have assumed the Hopewell culture (c. 100 BC-AD 400) built the mound, based principally on its proximity to the Newark Earthworks. The Hopewell culture, however, is not known to have built other effigy mounds. Limited excavations in 1999 revealed details of mound stratigraphy and recovered charcoal embedded in mound fill near the base of the mound. This charcoal yielded radiocarbon dates that average between AD 1170 and 1270, suggesting that the Late Prehistoric Fort Ancient culture (c. AD 1000-1550) made the mound. This result coincides with dates obtained for Serpent Mound in southern Ohio and suggests that the construction of effigy mounds in eastern North America was restricted to the Late Woodland and Late Prehistoric traditions. Ethnographic and ethnohistoric analogies suggest that the so-called 'Alligator' might actually represent the Underwater Panther and have served as a shrine for invoking the aid of supernatural powers.

Water scarcity and sustainability in the arid area of North America: Insights gained from a cross border perspective

2017 ◽  
Vol 7 (1) ◽  
pp. 6-18 ◽  
Author(s):  
Alejandro Yáñez-Arancibia ◽  
John W. Day
Keyword(s):  
Climate Change ◽  
North America ◽  
Water Scarcity ◽  
Economic Change ◽  
American Southwest ◽  
Arid Area ◽  
Border Region ◽  
Cross Border ◽  
Sharp Focus ◽  
The Face

The arid border region that encompasses the American Southwest and the Mexican northwest is an area where the nexus of water scarcity and climate change in the face of growing human demands for water, emerging energy scarcity, and economic change comes into sharp focus.

Palaeolithic Big Game Hunting at HP766 in Wadi Umm Rahau, Northern Sudan

2012 ◽  
Vol 10 (2) ◽  
pp. 165-174 ◽  
Author(s):  
Achilles Gautier ◽  
Daniel Makowiecki ◽  
Henryk Paner ◽  
Wim Van Neer
Keyword(s):  
Late Prehistoric ◽  
Large Mammals ◽  
Radiocarbon Dates ◽  
Large Size ◽  
Animal Bone ◽  
Game Hunting ◽  
Big Game Hunting ◽  
Bone Remains

HP766, discovered by the Gdansk Archaeological Museum Expedition (GAME) in the region immediately upstream the Merowe Dam in North Sudan and now under water, is one of the few palaeolithic sites with animal bone remains in the country. The archaeological deposits, the large size of the site, the lithics and the radiocarbon dates indicate occupation of a silt terrace of the Nile in late MSA and perhaps LSA times. Large and very large mammals predominate markedly among the recovered bone remains and it would seem that the palaeolithic hunters focused on such game. They could corner these animals on the site which is partially surrounded by high bedrock outcrops. Moreover swampy conditions of the site after the retreat of the annual Nile flood may have rendered less mobile the prey animals. According to this scenario, HP766 would testify to the ecological skills and generational memory of late prehistoric man in Sudan.

scholarly journals The duration of the active phase on surge-type glaciers: contrasts between Svalbard and other regions

1991 ◽  
Vol 37 (127) ◽  
pp. 388-400 ◽  
Author(s):  
Julian A. Dowdeswell ◽  
Gordon S. Hamilton ◽  
Jon Ove Hagen
Keyword(s):  
Time Series ◽  
North America ◽  
Active Phase ◽  
Aerial Photographs ◽  
Polar Ice ◽  
Phase Duration ◽  
Field Surveys ◽  
The World ◽  
Glacier Surges ◽  
Fast Motion

AbstractMany glaciers in Svalbard and in other glacierized areas of the world are known to surge. However, the time series of observations required to assess the duration of fast motion is very restricted. Data on active-phase duration in Svalbard come from aerial photographs, satellite imagery, field surveys and airborne reconnaissance. Evidence on surge duration is available for eight Svalbard ice masses varying from 3 to 1250 km2. Worldwide, active-phase duration is recorded for less than 50 glaciers. Few observations are available on high polar ice masses. The duration of the active phase is significantly longer for Svalbard glaciers than for surge-type glaciers in other areas from which data are available. In Svalbard, the active phase may last from 3 to 10 years. By contrast, a surge duration of 1–2 years is more typical of ice masses in northwest North America, Iceland and the Pamirs. Ice velocities during the protracted active phase on Svalbard glaciers are considerably lower than those for many surge-type glaciers in these other regions. Mass is transferred down-glacier more slowly but over a considerably longer period. Svalbard surge-type glaciers do not exhibit the very abrupt termination of the active phase, over periods of a few days, observed for several Alaskan glaciers. The duration of the active phase in Svalbard is not dependent on parameters related to glacier size. The quiescent phase is also relatively long (50–500 years) for Svalbard ice masses. Detailed field monitoring of changing basal conditions through the surge cycle is required from surge-type glaciers in Svalbard in order to explain the significantly longer length of the active phase for glaciers in the archipelago, which may also typify other high polar ice masses. The finding that surge behaviour, in the form of active-phase duration, shows systematic differences between different regions and their environments has important implications for understanding the processes responsible for glacier surges.

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