Collapse and continuity: A multi-proxy reconstruction of settlement organization and population trajectories in the Northern Fertile Crescent during the 4.2kya Rapid Climate Change event

The rise and fall of ancient societies have been attributed to rapid climate change events. One of the most discussed of these is the 4.2kya event, a period of increased aridity and cooling posited as the cause of societal changes across the globe, including the collapse of the Akkadian Empire in Mesopotamia. Studies seeking to correlate social and climatic changes around the 4.2kya event have tended to focus either on highly localized analyses of specific sites or surveys or more synthetic overviews at pan-continental scales, and temporally on the event and its aftermath. Here we take an empirical approach at a large spatial scale to investigate trends in population and settlement organization across the entirety of Northern Fertile Crescent (Northern Mesopotamia and the Northern Levant) from 6,000 to 3,000 cal BP. We use Summed Probability Distributions of radiocarbon dates and data from eighteen archaeological surveys as proxies for population, and a dataset of all settlements over ten hectares in size as a proxy for the degree of urbanization. The goal is to examine the spatial and temporal impact of the 4.2kya event and to contextualize it within longer term patterns of settlement. We find that negative trends are visible during the event horizon in all three proxies. However, these occur against a long-term trend of increased population and urbanization supported through unsustainable overshoot and the exploitation of a drier zone with increased risk of crop failure. We argue that the 4.2kya event occurred during a period of unprecedented urban and rural growth which may have been unsustainable even without an exogenous climate forcing

Holocene regional population dynamics and climatic trends in the Near East: a first comparison using archaeo-demographic proxies

This paper illustrates long-term trends in human population and climate from the Late Pleistocene to the Late Holocene (14,000-2500 cal. yr. BP) in order to assess to what degree climate change impacted human societies in the Near East. It draws on a large corpus of archaeodemographic data, including anthropogenic radiocarbon dates (n=10,653) and archaeological site survey (n=22,533), and 16 hydro-climatic records from cave speleothems and lake sediments. Where possible, inferred population dynamics and climatic trends have been made spatially congruent, and their relationships have been statistically tested. Demographic proxies and paleoclimatic records have been compared for the greater Near East as a whole and for seven major geo-cultural regions (Anatolia, Arabia, Cyprus, Iran, Levant, Mesopotamia, and South Caucasus). This approach allows us to identify regionalised patterns in population and climate trends. The results suggest a clear relationship between population and climate in the Late Pleistocene and Early Holocene (14,000-8326 cal. yr. BP) with population increasing in concomitance with wetter climatic conditions. During the Middle Holocene (8326-4200 cal. yr. BP) there is an increased regionalisation of demographic patterns, followed by marked interregional contrasts in the Late Holocene (4200-2500 cal. yr. BP). We identify a decoupling of demographic and climatic trends from the Middle Holocene onwards, and relate this to the existence of more complex societies. These were less vulnerable to gradual climatic shifts due to their logistical infrastructure, social organisation and technological capacity. We also assess the impact of five Rapid Climate Changes (RCC) which occurred during the study period on population levels. Although all five RCC (the so-called 10.2 k, 9.2 k, 8.2 k, 4.2 k, and 3.2 k cal. yr. BP events) are visible to some degree in our palaeoclimatic and demographic proxies, there are marked regional variations in magnitude and duration

Long-term trends in settlement persistence in Southwest Asia: Implications for sustainable urbanism, past, present and future

Southwest Asia saw the emergence of large settlements in the Early Holocene, and the world’s first urban communities around 6000 years ago, with cities a feature of the region ever since. These developed in diverse environmental settings, including the dry-farming plains of Northern Mesopotamia, the irrigated alluvium of Southern Mesopotamia and the more variegated landscapes of the Levant. In this paper we use a dataset of several hundred sites dating from the earliest large sites around 12,000 years ago to the Classical period (2000 BP), to examine trends in settlement sustainability through time. We use persistence of occupation as a proxy for sustainability and compare settlement trajectories in different land use zones. Comparing cities and settlements at these spatial and temporal scales allows us to address a key question in the New Urban Agendas framework: how urban development can best be supported by sustainable use of land. We find that the highest levels of persistence were not uniformly associated with high agricultural productivity regions, and some of the longest-lived settlements are located in marginal environments, likely at critical points in transport networks. We also find that persistence is enhanced in landscapes which do not require large-scale capital investment or specific forms of economic and social organisation to maintain high levels of agricultural productivity, and that sustainability is inversely correlated with social complexity. Our results show that the millennial timescales available through archaeology can enable us to identify the political, social and ecological conditions required for large centres to persist through time