Los modos de vida marítimos que caracterizaron a los archipiélagos occidentales de Patagonia comenzaron su desarrollo a mediados del Holoceno medio. El registro arqueológico sugiere posibles orígenes tanto en el extremo sur como en el extremo norte del territorio insular. La propuesta de un núcleo ecotonal septentrional de maritización se fundamentó en el hallazgo de sitios con tempranas ocupaciones de especialización litoral, entre los que destacó el conchal de Puente Quilo-1. Este artículo presenta resultados de nuevas excavaciones realizadas con el objeto de precisar su cronología, historia ocupacional y relevancia en la comprensión del proceso de maritización y colonización de los archipiélagos. A través de su integración con investigaciones previas en el sitio, los nuevos datos muestran una secuencia de reocupación estrechamente ligada a cambios en el paisaje producto de la variación en los niveles marinos, y caracterizan un campamento con diversidad funcional y diferenciación de áreas de actividad, inserto en un contexto de expansión regional de grupos cazadores-recolectores marinos. Los atributos culturales y su cronología permiten robustecer la hipótesis de un núcleo de maritización en el norte de la franja archipelágica.

Se presentan los resultados de las investigaciones llevadas a cabo en dos sitios del Holoceno medio ubicados en la cuenca superior del Río Loa (norte de Chile), conocidos como Alero Huiculunche y Corte de La Damiana. Los trabajos desarrollados incluyeron excavaciones estratigráficas, obtención y análisis de dataciones radiocarbónicas y análisis del material lítico y arqueofaunístico recuperado. Las dataciones obtenidas hicieron posible desarrollar un modelo cronológico bayesiano, el que permite definir los límites temporales más probables de ocupación para cada asentamiento y para sus unidades estratigráficas. La ocupación de Alero Huiculunche se muestra más temprana que en Corte de La Damiana, si bien el modelo revela alta probabilidad de una coexistencia breve entre las poblaciones de ambos sitios. Los análisis líticos y arqueofaunísticos sugieren que se trata en ambos casos de campamentos base de ocupación reiterada pero posiblemente intermitente, con ocupaciones menos intensas y/o recurrentes en Alero Huiculunche en relación con Corte de La Damiana. El conjunto de evidencias apunta a la existencia de un proceso de intensificación económica creciente entre aproximadamente 8000 y 5500 cal aP, el cual decanta en un sistema de asentamiento de mayor estabilidad y densidad ocupacional, en especial a partir de 6500 cal aP.

Past 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.

Seasonal climate variability is an important component of Earth's climate system, and has a significant impact on ecosystems and social systems. However, the temporal resolution of most proxy-based paleoclimate records is limiting to fully understand the past seasonal changes. Here, we used high-precision monthly resolution Sr/Ca records of three Tridacna squamosa specimens from the northern South China Sea (SCS) to reconstruct the sea surface temperature (SST) seasonality during three time periods from the middle Holocene. The results suggested that SST seasonality in the northern SCS during the middle Holocene (3.21 ± 0.98°C) was smaller than that for recent decades (AD 1994–2004, 4.32 ± 0.59°C). Analysis of modern instrumental data showed that the SST seasonality in the northern SCS was dominated by the winter SST, which was deeply influenced by the intensity of East Asian winter monsoon (EAWM). A strong EAWM usually resulted in cooler winter SST and a larger SST seasonality in the northern SCS. The reconstructed Holocene EAWM records showed that the EAWM strengthened from the middle to late Holocene, which was seen in our reconstruction of less SST seasonality changes during the middle Holocene in the northern SCS. This study highlighted that the Sr/Ca ratios from Tridacna shells can be used as a potential high-resolution indicator of past seasonal climate changes.

North-western Arabia is marked by thousands of prehistoric stone structures. Of these, the monumental, rectilinear type known as mustatils has received only limited attention. Recent fieldwork in AlUla and Khaybar Counties, Saudi Arabia, demonstrates that these monuments are architecturally more complex than previously supposed, featuring chambers, entranceways and orthostats. These structures can now be interpreted as ritual installations dating back to the late sixth millennium BC, with recent excavations revealing the earliest evidence for a cattle cult in the Arabian Peninsula. As such, mustatils are amongst the earliest stone monuments in Arabia and globally one of the oldest monumental building traditions yet identified.

Se presenta el análisis de 21 puntas de proyectil San Martín provenientes de la cuenca de Salinas Grandes (Salta, Argentina), asignables a finales del Holoceno temprano e inicios del Holoceno medio. Se obtuvo información novedosa mediante el examen de (1) variedad de rocas, (2) inversión de trabajo en manufactura, y (3) sistemas de armas. Se plantea la selección de rocas locales y de tenacidad intermedia, la aplicación de diferentes modalidades de formatización y un mayor sustento como armas de mano y lanza arrojadiza. En conjunto con la evidencia regional, las piezas analizadas serían consecuencia de un proceso de diversificación de clases de puntas de proyectil ocurrido en un contexto de cambio ambiental.

We present a continuous, sediment core-based record of paleohydroclimate spanning ~5800 cal yr BP to recent from Lower Pahranagat Lake (LPAH), a shallow, alkaline lake in southern Nevada. We apply stable isotopes (δ18O and δ13C) from fine-fraction authigenic carbonate, which are sensitive recorders of hydroclimatic variability in this highly evaporative region. Additional geochemical proxies (total organic carbon, C/N, and total inorganic carbon) provide supporting information on paleoecological change in and around the lake. Our data suggest progressively wetter conditions starting at the later part of the middle Holocene and extending into the late Holocene (~5500–3350 cal yr BP) followed by a millennial-scale dry period from ~3150 to 1700 cal yr BP. This latter interval encompasses the ‘Late Holocene dry period’ (LHDP) reported by other investigators, and our data help refine the area affected in this episode. Our data also show evidence for a series of century-scale fluctuations in regional hydroclimate, including wet and dry intervals between 2350 and 1600 cal yr BP, and drier conditions over the past few centuries. Paleohydroclimate trends in the LPAH record show correspondence with those from the central Great Basin to the north, suggesting that both areas were subject to similar climatic forcings.

Archaeological investigations in Camels Back Cave, western Utah, recovered a series of small-mammal bone assemblages from stratified deposits dating between ca. 12,000 and 500 14C yr B.P. The cave's early Holocene fauna includes a number of species adapted to montane or mesic habitats containing grasses and/or sagebrush (e.g., Lepus townsendii, Marmota flaviventris, Reithrodontomys megalotis, and Brachylagus idahoensis) which suggest that the region was relatively cool and moist until after 8800 14C yr B.P. Between ca. 8600 and 8100 14C yr B.P. these mammals became locally extinct, taxonomic diversity declined, and there was an increase in species well-adapted to xeric, low-elevation habitats, including ground squirrels, Lepus californicus and Neotoma lepida. The early small-mammal record from Camels Back Cave is similar to the 11,300–6000 14C yr B.P. mammalian sequence from Homestead Cave, northwestern Utah, and provides corroborative data on Bonneville Basin paleoenvironments and mammalian responses to middle Holocene desertification.

The climate of the Great Plains during the middle Holocene varied considerably, but overall it was marked by a north–south gradient of increasingly warmer and drier conditions, with a reduction in effective moisture, surface water, and resource abundance, and an increase in resource patchiness, sediment weathering, erosion, and aeolian activity. Pronounced drought conditions were most evident on the Southern High Plains. Understanding the human responses to middle Holocene climates is complicated by a lack of archaeological data, which is partly a result of geomorphic processes that removed or deeply buried sites of this age, and by the varying adaptive responses of hunter-gatherers during this period. On the Southern High Plains, where drought was most severe, surface and groundwater sources dried and bison populations were diminished, prompting substantial adaptive changes, including local abandonment, well-digging to tap underground water, and a widening of the diet breadth to incorporate higher-cost, lower-return seed and plant resources. Sites of this age on the Central and Northern Plains also show a possible increase in diet breadth (with the incorporation of plant foods in the diet), and perhaps changes in settlement mobility (including possible shift into higher elevation areas, or mapping-on to extant rivers and springs). But linking those changes to middle Holocene drought is less straightforward.

During the Holocene, bison (Bison bison) were key components of the Great Plains landscape. This study utilizes serial stable isotope analyses (tooth enamel carbonate) of 29 individuals from five middle Holocene (∽ 7–8.5·ka) archaeological sites to address seasonal variability in movement patterns and grazing behavior of bison populations in the eastern Great Plains. Stable carbon isotopes (δ13C) indicate a bison diet that is similar to the C3/C4 composition of modern tallgrass prairies, while 87Sr/86Sr values generally indicate very little seasonal movement (b50 km) and relatively limited inter-annual movement (b500 km) over the course of 4–5 yr. Analyses of variability in serial stable oxygen isotope samples (δ18O) further substantiate a model of localized bison herds that adhered to upland areas of the eastern Plains and prairie–forest border.

The hydrogeochemical characteristics of the Cabo de Gata coastal aquifer (southeastern Spain) were studied in an attempt to explain the anomalous salinity of its groundwater. This detritic aquifer is characterised by the presence of waters with highly contrasting salinities; in some cases the salinity exceeds that of seawater. Multivariate analysis of water samples indicates two groups of water (G1 and G2). Group G1 is represented in the upper part of the aquifer, where the proportion of seawater varies between 10 and 60%, whilst G2 waters, taken from the lower part of the aquifer, contain 60−70% seawater. In addition, hydrogeochemical modelling was applied, which reveals that the waters have been subject to evaporation between 25 and 35%. There was a good agreement between the modelled results and the observed water chemistry. This evaporation would have occurred during the Holocene, in a coastal lagoon environment; the resulting brines would have infiltrated into the aquifer and due to their greater density, sunk towards the impermeable base. The characteristics of this water enabled us to reconstruct the interactions that must have occurred between the coastal aquifer and the lagoon, and to identify the environmental conditions that prevailed in the study area during the Middle Holocene.

Approximately 70 km of new decimeter-resolution seismic reflection profile data from Owasco Lake, New York define a middle Holocene (∼4600 14C yr B.P.) erosion surface in the north end of the lake at water depths as great as 26 m. Beneath the lake, post-glacial sediments are up to 9 m thick and represent about 10% of the total sediment fill. Early to middle Holocene sediments, ∼6 m thick, contain biogenic gas at the south end of the basin and a large (4 km × 300 m × 15 m) subaqueous slide deposit along the east-central portion of the lake. Late Holocene sediments are thinner or absent, particularly at the north end of the lake. The middle Holocene erosion surface may have been produced by a drop in lake level. Alternatively, it may represent a change in climate during the transition between the relatively warm Holocene hypsithermal and cool neoglacial. At this time (∼4600 14C yr B.P.) circulation in Owasco Lake appears to have evolved from sluggish to active. The increased circulation, which persists today, probably resulted from atmospheric cold fronts with strong southwesterly winds that piled up water at the north end of the lake. The increased water circulation may have been ultimately driven by decreasing insolation, which produced an increased pole-to-equator thermal gradient and thus, stronger global winds that began at the transition between the hypsithermal and neoglacial.

Using a detailed excavated sequence and a broad range of south Andean sites, the authors show that changes in the bones of camelids and in the lithic assemblages offer an account of how animals were intensively exploited and ultimately domesticated between the sixth and fourth millennia BP.