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Was the spread of agropastoralism from the Fertile Crescent throughout Europe influenced by extreme climate events, or was it independent of climate? We here generate idealized climate events using palaeoclimate records. In a mathematical model of regional sociocultural development, these events disturb the subsistence base of simulated forager and farmer societies. We evaluate the regional simulated transition timings and durations against a published large set of radiocarbon dates for western Eurasia; the model is able to realistically hindcast much of the inhomogeneous space-time evolution of regional Neolithic transitions. Our study shows that the consideration of climate events improves the simulation of typical lags between cultural complexes, but that the overall difference to a model without climate events is not significant. Climate events may not have been as important for early sociocultural dynamics as endogenous factors., Revised version submitted to the Journal of Archaeological Science, special issue on The World Reshaped: impacts of the Neolithic transition. 10 pages, 4 figures, 1 table + supplementary material

Despite the fact that Europe and Eastern North America both have similar woodland environments, the emergence of agriculture in these areas proceeded very differently varying in timing, speed, and mechanism. To analyze the different subsistence paths the Global Land Use and Technological Evolution Simulator was used, a numerical model for simulating demography, innovation, domestication, migration and trade within the geoenvironmental context. I demonstrate how Europe receives a large package of foreign domesticates and converts rapidly. In contrast, trajectories relating to Eastern North America exhibit a gradual transition in which hunting and gathering and agropastoralism coexist for a long period of time, and agriculture is integrated slowly into the existing subsistence scheme. I deduce from this a qualitative economic difference in the two regional transitions: limited population size in Europe, limited resources in Eastern North America.

Was the spread of agropastoralism from the Eurasian founder regions dominated by demic or by cultural diffusion? This study employs a mathematical model of regional sociocultural development that includes different diffusion processes, local innovation and societal adaptation. Simulations hindcast the emergence and expansion of agropastoral life style in 294 regions of Eurasia and North Africa. Different scenarios for demic and diffusive exchange processes between adjacent regions are contrasted and the spatiotemporal pattern of diffusive events is evaluated. This study supports from a modeling perspective the hypothesis that there is no simple or exclusive demic or cultural diffusion, but that in most regions of Eurasia a combination of demic and cultural processes were important. Furthermore, we demonstrate the strong spatial and temporal variability in the balance of spread processes. Each region shows sometimes more demic, and at other times more cultural diffusion. Only few, possibly environmentally marginal, areas show a dominance of demic diffusion. This study affirms that diffusion processes should be investigated in a diachronic fashion and not from a time-integrated perspective., 9 pages, 3 figures, revised version submitted to Documenta Prehistoric

During the Holocene strong gradients in the distribution of technologyincluding subsistence ways emerged on a global scale.These patterns were further amplified in historic times and are stillvisible through worldwide differences in national wealth.In order to evaluate major factors responsible for the shift fromforaging to food production we here employ quantitative methods bydeveloping a deterministic but simple model. After compiling existing maps of potential vegetation at 5000 BP theinhabited world is split into 197 regions with homogeneous environmentalconditions. Suitable variables for the macro-economic and culturaldevelopment in the Neolithic period are found to be farming to hunting-gatheringratio, number of agricultural economies and a technological development index.The model explicitly describes economic adaptation, growth and migrationof human populations together with the spread of their cultural characteristics; it accounts for over-exploitation of natural resources, crowdingmortality and the climate variability on a millennium scale.In a thorough model validation region specific trajectories are compared toarchaeological evidence revealing a high correspondence. Major parts of the knownsequence of Neolithic centers including the timing differences are robustlyreproduced. A series of known problems in prehistory is discussedcomprising the lag between domestication and full scale farming, the off-levelingof the technological boost following the transition, the emergence ofdistinct migration waves and sensitivity to climate fluctuations.Not mere population pressure but continuous innovation and competition betweensubsistence strategies is identified as a prime mover of agricultural development.The results suggest that few aspects of biogeography may have determined theobserved continental gradients in the number of domesticable species ultimatelyleading to an increasing differentiation in technology and demography.

The relationship between humans and their environment underwent a radical change during the last 10,000 years: from mobile and small groups of foragers to sedentary extensive cultivators and on to high-density intensive agriculture-based modern society; these transitions fundamentally transformed the formerly predominantly passive human user of the environment into an active component of the Earth system. The most striking impacts of these global transitions have only become visible and measurable during the last 150 years (Crutzen, Nature 415:23, 2002; Crutzen and Stoermer, IGBP Newsletter 41(1):17–18, 2000). Prior to this time frame, the use of forest resources for metal smelting in early Roman times and the extensive medieval agricultural system had already changed the landscape (Barker, Nature 473:163–164, 2011; Kaplan et al., Quaternary Science Reviews 28(27/28):3016–3034, 2009); the global climate effects of these early extensive cultivation and harvesting practices are still under debate (Kaplan et al., The Holocene 21(5):775–791, 2011; Lemmen, Géomorphologie: relief, processus, environnement 2009(4):303–312, 2010; Ruddiman, Climatic Change 61(3):261–293, 2003; Stocker et al., Biogeosciences 8:69–88, 2011).

The Indus Valley Civilization (IVC) was one of the first great civilizations in prehistory. This bronze age civilization flourished from the end of the fourth millennium BC. It disintegrated during the second millennium BC; despite much research effort, this decline is not well understood. Less research has been devoted to the emergence of the IVC, which shows continuous cultural precursors since at least the seventh millennium BC. To understand the decline, we believe it is necessary to investigate the rise of the IVC, i.e., the establishment of agriculture and livestock, dense populations and technological developments 7000--3000 BC. Although much archaeological information is available, our capability to investigate the system is hindered by poorly resolved chronology, and by a lack of field work in the intermediate areas between the Indus valley and Mesopotamia. We thus employ a complementary numerical simulation to develop a consistent picture of technology, agropastoralism and population developments in the IVC domain. Results from this Global Land Use and technological Evolution Simulator show that there is (1) fair agreement between the simulated timing of the agricultural transition and radiocarbon dates from early agricultural sites, but the transition is simulated first in India then Pakistan; (2) an independent agropastoralism developing on the Indian subcontinent; and (3) a positive relationship between archeological artifact richness and simulated population density which remains to be quantified.

The role of Pre- and Protohistoric anthropogenic land cover changes needs to be quantified i) to establish a baseline for comparison with current human impact on the environment and ii) to separate it from naturally occurring changes in our environment. Results are presented from the simple, adaptation-driven, spatially explicit Global Land Use and technological Evolution Simulator (GLUES) for pre-Bronze age demographic, technological and economic change. Using scaling parameters from the History Database of the Global Environment as well as GLUES-simulated population density and subsistence style, the land requirement for growing crops is estimated. The intrusion of cropland into potentially forested areas is translated into carbon loss due to deforestation with the dynamic global vegetation model VECODE. The land demand in important Prehistoric growth areas - converted from mostly forested areas - led to large-scale regional (country size) deforestation of up to 11% of the potential forest. In total, 29 Gt carbon were lost from global forests between 10 000 BC and 2000 BC and were replaced by crops; this value is consistent with other estimates of Prehistoric deforestation. The generation of realistic (agri-)cultural development trajectories at a regional resolution is a major strength of GLUES. Most of the pre-Bronze age deforestation is simulated in a broad farming belt from Central Europe via India to China. Regional carbon loss is, e.g., 5 Gt in Europe and the Mediterranean, 6 Gt on the Indian subcontinent, 18 Gt in East and Southeast Asia, or 2.3 Gt in subsaharan Africa. Le rôle de l’Homme dans l’évolution des états de surface de la Terre au cours de la Pré- et Protohistoire doit être estimé afin de répondre à deux objectifs : 1) établir une base de données qui permette de comparer les différentes actions anthropiques sur l’environnement et 2) bien distinguer les causes « naturelles » des causes d’origine anthropique dans l’évolution des dynamiques environnementales. L’utilisation d’un logiciel intitulé « Global Land Use and technological Evolution Simulator (GLUES) » a permis de modéliser les changements démographiques, technologiques et économiques antérieurs à l’Âge du Bronze. La démarche a consisté à estimer le besoin en terres pour répondre à la croissance continue de mises en culture en se basant sur les données de la « History Database of the Global Environment » et sur la modélisation des densités de population et des types de subsistance estimées d’après GLUES. Les défrichements forestiers se sont traduits par une perte de carbone estimée grâce au modèle VECODE. Le besoin en terres dans les foyers d’expansion préhistoriques - développés principalement dans des secteurs forestiers - a conduit à des déforestations massives, représentant jusqu’à 11 % de l’ensemble des forêts potentielles. Sur la période 10 000-2000 av. J.-C., ce sont au total environ 29 Gt de carbone qui ont été perdues en raison de la substitution des champs cultivés aux forêts. GLUES a permis la visualisation d’axes d’expansion agricole à une échelle régionale. La plupart des défrichements observés avant l’Age du Bronze ont affecté un vaste territoire qui s’étend depuis l’Europe centrale jusqu’à la Chine, en passant par l’Inde. Les valeurs régionales de perte en carbone sont estimées à 5 Gt en Europe et en Méditerranée, à 6 Gt en Inde, à 18 Gt en Asie du sud et du sud-est et à 2,3 Gt pour l’Afrique subsaharienne.

We integrate 130 globally distributed proxy time series to refine the understanding of climate variability during the Holocene. Cyclic anomalies and temporal trends in periodicity from the Lower to the Upper Holocene are extracted by combining Lomb-Scargle Fourier-transformed spectra with bootstrapping. Results were cross-checked by counting events in the time series. Main outcomes are: First, the propensity of the climate system to fluctuations is a region specific property. Many records of adjacent sites reveal a similar change in variability although they belong to different proxy types (e.g., δ18O, lithic composition). Secondly, at most sites, irreversible change occured in the Mid-Holocene. We suggest that altered ocean circulation together with slightly modified coupling intensity between regional climate subsystems around the 5.5 kyr BP event (termination of the African Humid Period) were responsible for the shift. Fluctuations especially intensified along a pan-American corridor. This may have led to an unequal crisis probability for early human civilizations in the Old and New World. Our study did not produce evidence for millennial scale cyclicity in some solar activity proxies for the Upper Holocene, nor for a privileged role of the prominent 250, 550, 900 and 1450 yr cycles. This lack of global periodicities corroborates the regional character of climate variability.