Coping with arid environments: A critical threshold for human expansion in Europe at the Marine Isotope Stage 12/11 transition? The case of the Iberian Peninsula.

Archaeological remains have highlighted the fact that the interglacial Marine Isotope Stage (MIS) 11 was a threshold from the perspective of hominin evolution in Europe. After the MIS 12 glaciation, considered one of the major climate-driven crises experienced by hominins, the archaeological records show an increasing number of occupations, evidence of new subsistence behaviors, and significant technical innovations. Here, we used statistical and geographic techniques to analyze the amphibian- and reptile-based paleoclimate and habitat reconstructions generated from a large data set of the Iberian Peninsula to (1) investigate if temperature, precipitation, and/or forest cover may have impacted the hominin occupation of the territory during the Early and Middle Pleistocene, (2) propose an 'Iberian' ecological model before and after the MIS 12/11 transition, and (3) evaluate, based on this model, the potential hominin occupation at a European scale. The results indicate the existence of climatic constraints on human settlement related to rainfall and environmental humidity. The Early Pleistocene and the first half of the Middle Pleistocene are dominated by the occupation of relatively humid wooded areas, whereas during the second part of the Middle Pleistocene, a broadening of the earlier ecological niche is clearly observed toward the occupation of more open arid areas. Based on the estimated occupational niche for hominins, a maximum potential distribution for early hominins is proposed in Europe before and after 426 ka. Results also indicate that parts of the Iberian Peninsula may not have been suitable for early hominin occupation. Our ecological model is consistent with the pattern of hominin occupation observed in northern and central Europe, where the earliest evidence reflects only pioneering populations merely extending their ranges in response to the expansion of their preferred habitats, as compared with a more sustained occupation by 400 ka.

Geochemical and sedimentary constraints on the formation of the Venta Micena early Pleistocene site (Guadix-Baza Basin, Spain).

Despite the paleontological relevance of the terrestrial Early Pleistocene Venta Micena bonebed (Baza Basin, Spain), it lacks a comprehensive geochemical/sedimentological study. Here, we demonstrate that the 1.5-m-thick Venta Micena limestone formed in a relatively small freshwater wetland/pond located at the periphery of the large saline Baza paleolake. Two microfacies are observed, with high and low contents of invertebrate fossils, and which originated in the centre and margin of the wetland, respectively. X-ray diffraction (XRD) mineralogy and paleohydrological characterization based on ostracod and bulk-rock geochemistry (δ13C and δ18O) indicate that the limestone reflects a general lowstand of the Baza lake, permitting the differentiation of freshwater wetlands that were fed by adjacent sources. Conversely, during highstands, the Baza lake flooded the Venta Micena area and the freshwater fauna was replaced by a saline one. Bulk-rock isotopic data indicate that the lower interval C1 of the limestone (bone-rich in marginal settings) displays general negative values, while the upper interval C2 (bone free) displays less negative values. The bones of predated mammals accumulated in the marginal areas, which were flooded and buried by recurring water-table fluctuations. Lake dynamics played a critical role in bone accumulation, which was previously considered as representing a hyena den.

Taphonomic and spatial analyses from the Early Pleistocene site of Venta Micena 4 (Orce, Guadix-Baza Basin, southern Spain).

Venta Micena is an area containing several palaeontological sites marking the beginning of the Calabrian stage (Early Pleistocene). The richness of the fossil accumulation including species of Asian, African and European origin, makes Venta Micena a key site for the the palaeoecological and palaeoenvironmental study of southern Europe during the Early Pleistocene. Thus, research has been focused on Venta Micena 3, which was originally interpreted as a single palaeosurface associated with a marshy context, in which most of the fauna was accumulated by Pachycrocuta brevirostris. Recent excavations have unearthed a new site, Venta Micena 4, located in the same stratigraphic unit (Unit C) and in close proximity to Venta Micena 3. Here we show the first analyses regarding the taphonomic and spatial nature of this new site, defining two stratigraphic boundaries corresponding to two different depositional events. Furthermore, the taphonomic analyses of fossil remains seem to indicate a different accumulative agent than Pachycrocuta, thus adding more complexity to the palaeobiological interpretation of the Venta Micena area. These results contribute to the discussion of traditional interpretations made from Venta Micena 3.

Subspheroids in the lithic assemblage of Barranco León (Spain): Recognizing the late Oldowan in Europe.

The lithic assemblage of Barranco León (BL), attributed to the Oldowan techno-complex, contributes valuable information to reconstruct behavioral patterning of the first hominins to disperse into Western Europe. This archaic stone tool assemblage comprises two, very different groups of tools, made from distinct raw materials. On the one hand, a small-sized toolkit knapped from Jurassic flint, comprising intensively exploited cores and small-sized flakes and fragments and, on the other hand, a large-sized limestone toolkit that is mainly linked to percussive activities. In recent years, the limestone macro-tools have been the center of particular attention, leading to a re-evaluation of their role in the assemblage. Main results bring to light strict hominin selective processes, mainly concerning the quality of the limestone and the morphology of the cobbles, in relation to their use-patterning. In addition to the variety of traces of percussion identified on the limestone tools, recurrences have recently been documented in their positioning and in the morphology of the active surfaces. Coupled with experimental work, this data has contributed to formulating hypothesis about the range of uses for these tools, beyond stone knapping and butchery, for activities such as: wood-working or tendon and meat tenderizing. The abundance of hammerstones, as well as the presence of heavy-duty scrapers, are special features recognized for the limestone component of the Barranco León assemblage. This paper presents, for the first time, another characteristic of the assemblage: the presence of polyhedral and, especially, subspheroid morphologies, virtually unknown in the European context for this timeframe. We present an analysis of these tools, combining qualitative evaluation of the raw materials, diacritical study, 3D geometric morphometric analysis of facet angles and an evaluation of the type and position of percussive traces; opening up the discussion of the late Oldowan beyond the African context.

The genomic history of the Iberian Peninsula over the past 8000 years.

We assembled genome-wide data from 271 ancient Iberians, of whom 176 are from the largely unsampled period after 2000 BCE, thereby providing a high-resolution time transect of the Iberian Peninsula. We document high genetic substructure between northwestern and southeastern hunter-gatherers before the spread of farming. We reveal sporadic contacts between Iberia and North Africa by ~2500 BCE and, by ~2000 BCE, the replacement of 40% of Iberia's ancestry and nearly 100% of its Y-chromosomes by people with Steppe ancestry. We show that, in the Iron Age, Steppe ancestry had spread not only into Indo-European-speaking regions but also into non-Indo-European-speaking ones, and we reveal that present-day Basques are best described as a typical Iron Age population without the admixture events that later affected the rest of Iberia. Additionally, we document how, beginning at least in the Roman period, the ancestry of the peninsula was transformed by gene flow from North Africa and the eastern Mediterranean.

Neurocranium versus Face: A Morphometric Approach with Classical Anthropometric Variables for Characterizing Patterns of Cranial Integration in Extant Hominoids and Extinct Hominins.

The relative importance of the two main cranial complexes, the neurocranium and the splanchnocranium, has been examined in the five species of extant hominoids and in a huge sample of extinct hominins using six standard craniometric variables that measure the length, width and height of each cranial module. Factor analysis and two-block partial least squares were used for establishing the major patterns of developmental and evolutionary integration between both cranial modules. The results obtained show that all extant hominoids (including the anatomically modern humans) share a conserved pattern of developmental integration, a result that agrees with previous studies. The pattern of evolutionary integration between both cranial modules in australopiths runs in parallel to developmental integration. In contrast, the pattern of evolutionary and developmental integration of the species of the genus Homo is the opposite, which is probably the consequence of distinctive selective regimes for both hominin groups.

On the relationships of postcanine tooth size with dietary quality and brain volume in primates: implications for hominin evolution.

Brain volume and cheek-tooth size have traditionally been considered as two traits that show opposite evolutionary trends during the evolution of Homo. As a result, differences in encephalization and molarization among hominins tend to be interpreted in paleobiological grounds, because both traits were presumably linked to the dietary quality of extinct species. Here we show that there is an essential difference between the genus Homo and the living primate species, because postcanine tooth size and brain volume are related to negative allometry in primates and show an inverse relationship in Homo. However, when size effects are removed, the negative relationship between encephalization and molarization holds only for platyrrhines and the genus Homo. In addition, there is no general trend for the relationship between postcanine tooth size and dietary quality among the living primates. If size and phylogeny effects are both removed, this relationship vanishes in many taxonomic groups. As a result, the suggestion that the presence of well-developed postcanine teeth in extinct hominins should be indicative of a poor-quality diet cannot be generalized to all extant and extinct primates.

Comparing two methods of univariate discriminant analysis for sex discrimination in an Iberian population.

This study assesses the performance of two analytical approaches to sex discrimination based on single linear variables: discriminant analysis and the Lubischew's test. Ninety individuals from an archaeological population (La Torrecilla-Arenas del Rey, Granada, southern Spain) and 17 craniometrical variables were included in the analyses. Most craniometrical variables were higher for men. The bizygomatic breadth enabled the highest level of discrimination: 87.5% and 88.5%, using discriminant analysis and Lubischew's test, respectively. Bizygomatic breadth proved highly dimorphic in comparison to other populations reported in the literature. Lubischew's test raised the discrimination percentage in specific craniometrical variables, while others showed a superior performance by means of the discriminant analysis. The inconsistent results across statistical methods resulted from the specific formulation of each procedure. Discriminant analysis accounts both for within-group and between-group variance, while Lubischew's test emphasizes between-group variation only. Therefore, both techniques are recommended, as they provide different means of achieving optimal discrimination percentages.

Tooth size and metabolic requirements in primates: the 'equivalence between exponents' under discussion / Tamaño de la dentición y requerimientos metabólicos en primates: la 'equivalencia entre exponentes' bajo discusión

The functional significance of teeth size, specifically postcanine tooth size has contributed a vast amount of scientific literature. Nevertheless, these studies have been based on 'equivalence between exponents'. That is, when the tooth size scales to the 0.75 power of body size exponent is interpreted as reflecting differences in metabolic requirements. On the contrary, if the obtained exponent is close to isometry, such slope is interpreted as that variation in teeth size is an incidental consequence of body size variation. In this paper, we show the results of a study in which the relationship between postcanine tooth occlusal area (PCOA) and basal metabolic rate (BMR) has been evaluated in 28 primate species. On one hand, the results obtained indicate that there is a high correlation between the BMR and the size of the PCOA, even when phylogenetic control tests are used, and that isometry cannot be discarded in both cases. However, if the effects of body mass are removed, a null slope cannot be discarded. On the other hand, when body mass (BM) is taken as the independent variable and PCOA as the dependent one, the slope obtained evidences a negative allometry, and this holds also when phylogenetic control is used. Given these contradictory results, we suggest that the rule of 'equivalence between exponents' is not a good approach for obtaining inferences on the function of postcanine teeth...

El significado funcional del tamaño de los dientes, y más concretamente del tamaño de la dentición poscanina, ha contribuido al desarrollo de una vasta literatura científica. No obstante, casi todos estos trabajos se han centrado en la 'equivalencia entre exponentes'. Así, cuando el tamaño de los dientes escala siguiendo una pendiente de 0,75 respecto al tamaño corporal se interpreta que las diferencias en tamaño reflejan los cambios en los requerimientos metabólicos. Si, por el contrario, el exponente obtenido es cercano a la isometría, la inferencia que se establece es que el cambio en el tamaño de la dentición es una consecuencia incidental del cambio en el tamaño corporal. En este artículo mostramos los resultados de un estudio en el que se han evaluado las relaciones entre el área de la dentición poscanina (PCOA) y la tasa metabólica basal (BMR) en 28 especies de primates. Los resultados obtenidos indican, en primer lugar, que existe una fuerte correlación entre BMR y PCOA, incluso cuando el efecto de la filogenia es controlado. Sin embargo, cuando se evita el efecto del tamaño no se puede descartar que la pendiente sea igual a cero. En segundo lugar, cuando se realiza una regresión usando el tamaño corporal (BM) como variable independiente y PCOA como dependiente, la pendiente obtenida es alométricamente negativa, lo que se mantiene cuando se controla para la filogenia. Dado que los resultados son contradictorios, sugerimos que la regla de la 'equivalencia entre exponentes' no es una buena aproximación para obtener inferencias sobre la función de la dentición poscanina...

Discriminación de sexo en una población medieval del sur de la Península Ibérica mediante el uso de variables simples / Sex discrimination in a middle age population of the Southern Iberian Peninsula by the use of simple variables

Las asignaciones de sexo a los restos osteológicos es fundamental puesto que suponen el primer paso hacia el establecimiento de otros tipos de inferencias biológicas y culturales. Aunque la determinación del sexo es relativamente fácil cuando se recuperan determinadas partes esqueléticas, especialmente la pelvis y el cráneo, resulta más problemática a partir de otros huesos, sobre todo si se trata de fragmentos. En este trabajo se presenta un estudio de discriminación del sexo de los individuos a partir del húmero utilizando variables simples. Los resultados muestran cómo, utilizando la prueba de Lubischew, cada una de las principales partes del húmero aporta, al menos, una variable con porcentajes de discriminación cercanos al 90 por ciento. Estos resultados se comparan con los obtenidos mediante análisis discriminantes. Desde el punto de vista de la aplicación en Arqueología, la prueba de Lubischew se presenta como una herramienta muy útil para la asignación de sexo a individuos de sexo desconocido pertenecientes a muestras suficientemente amplias, siempre y cuando existan asignaciones sexuales previas fiables para un porcentaje alto de los individuos de cada una de aquéllas.

Sex determination on osteological remains is key since it is the initial step to establish another kind of biological and cultural inferences. Though sex determination arises easily when some particular parts of the skeleton are collected, specifically the pelvis and the skull, this target is more difficult from other bones, specifically when they are fragmented. In the present paper a study on sex discrimination based on simple humeral variables is shown. The use of the Lubischew's test show that at least one variable in each part of the humerus provides a discriminant percentage close to 90 percent. These results are compared with those obtained by discriminanting analysis. From an archaeological point of view, the Lubischew's test is a useful tool to infer the sex of the uncertain individuals belonging to large enough samples with previous reliable sex assigments.