Understanding Fossil Phytolith Preservation: The Role of Partial Dissolution in Paleoecology and Archaeology

Opaline phytoliths are important microfossils used for paleoecological and archaeological reconstructions that are primarily based on relative ratios of specific morphotypes. Recent studies have shown that phytolith assemblages are prone to post-depositional alteration involving partial dissolution, however, the manner in which partial dissolution affects morphotype composition is poorly understood. Here we show that morphotype assemblages from four different plant species subjected to controlled partial dissolution are significantly different from the original assemblages, indicating that the stability of various morphotypes differs, mainly depending on their surface area to bulk ratios. This underlying mechanism produces distorted morphotype compositions in partially dissolved phytolith assemblages, bearing vast implications for morphotype-based paleoecological and archaeological interpretation. Together with analyses of phytolith assemblages from a variety of archaeological sites, our results establish criteria by which well-preserved phytolith assemblages can be selected for accurate paleoecological and archaeological reconstructions

Phytolith evidence for the pastoral origins of multi-cropping in Mesopotamia (ancient Iraq)

Multi-cropping was vital for provisioning large population centers across ancient Eurasia. In Southwest Asia, multi-cropping, in which grain, fodder, or forage could be reliably cultivated during dry summer months, only became possible with the translocation of summer grains, like millet, from Africa and East Asia. Despite some textual sources suggesting millet cultivation as early as the third millennium BCE, the absence of robust archaeobotanical evidence for millet in semi-arid Mesopotamia (ancient Iraq) has led most archaeologists to conclude that millet was only grown in the region after the mid-first millennium BCE introduction of massive, state-sponsored irrigation systems. Here, we present the earliest micro-botanical evidence of the summer grain broomcorn millet (Panicum miliaceum) in Mesopotamia, identified using phytoliths in dung-rich sediments from Khani Masi, a mid-second millennium BCE site located in northern Iraq. Taphonomic factors associated with the region’s agro-pastoral systems have likely made millet challenging to recognize using conventional macrobotanical analyses, and millet may therefore have been more widespread and cultivated much earlier in Mesopotamia than is currently recognized. The evidence for pastoral-related multi-cropping in Bronze Age Mesopotamia provides an antecedent to first millennium BCE agricultural intensification and ties Mesopotamia into our rapidly evolving understanding of early Eurasian food globalization

L'estudi dels processos de formació dels sediments arqueòlogics i dels paleosòls a partir de l'analisi dels fitòlits , els minerals i altres microrestes

L'estudi dels processos de formació és una peça clau per entendre el significat de les restes arqueològiques recuperades. En aquesta tesi s'aborda el problema dels processos de formació a partir dels fitòlits, la mineralogia (IR-FT) i les altres microrestes. A partir d'aquesta aproximació s'han pogut determinar els agents responsables dels processos de formació, s'han diferenciat els límits i avantatges en aquest camp i, finalment, s'han definit una sèrie d'aspectes metodològics necessaris per entendre la formació d'un jaciment a través dels fitòlits. Els jaciments estudiats (La Gorja d'Olduvai, El Abric Romaní, El Mirador i Tel Dor) formen part d'una escala on els diferents graus d'antropització permeten distingir els processos culturals dels naturals, però també ens aporten dades d'alta resolució d'esdeveniments de curta durada, així com ens ajuden a comprendre els processos tafonòmics que poden sofrir els fitòlits.El estudio de los procesos de formación es una pieza clave para entender el significado de los restos arqueológicos recuperados. En esta tesis se aborda el problema de los procesos de formación a partir de los fitolitos, la mineralogía (IR-FT) y los otro microrestos. A partir de esta aproximación se ha podido determinar los agentes responsables de los procesos de formación, se han diferenciado los límites y ventajas en este campo y, finalmente, se han definido una serie de aspectos metodológicos necesarios para entender la formación de un yacimiento a través de los fitolitos.Los yacimientos estudiados (La Garganta de Olduvai, El Abric Romaní, El Mirador y Tel Dor) forman parte de una escala donde los diferentes grados de antropización permiten diferenciar los procesos culturales de los naturales, pero también nos aportan datos de alta resolución de eventos de corta durada, así como nos ayudan a comprender los procesos tafonómicos que pueden sufrir los fitolitos.The study of site formation processes is a key point to understand the meaning of the recovered archaeological remains. In this thesis we approach to the subject of the archaeological formation processes through the phytolith analyses, the mineralogy (FTIR) and, other micro-remains. Using this approach we have determined the agents responsible of the formation processes, the limitations and advantages have been differentiated, and, finally, we have defined a set of methodological aspects necessary to understand the formation of archaeological sites through the phytolith analyses.The studied sites (Olduvai Gorge, Abric Romaní, El Mirador and Tel Dor) form part of a scale where the different degrees of human impacts allow us to differentiate the natural and cultural formation processes. In addition, we have obtained high resolution data of short-term events, and also it has been possible to understand the taphomomic processes that phytoliths may experience

Phytoliths as an indicator of early modern humans' plant gathering strategies, fire fuel and site occupation intensity during the Middle Stone Age at Pinnacle Point 5-6 (south coast, South Africa)

The study of plant remains in archaeological sites, along with a better understanding of the use of plants by prehistoric populations, can help us shed light on changes in survival strategies of hunter-gatherers and consequent impacts on modern human cognition, social organization, and technology. The archaeological locality of Pinnacle Point (Mossel Bay, South Africa) includes a series of coastal caves, rock-shelters, and open-air sites with human occupations spanning the Acheulian through Middle Stone Age (MSA) and Later Stone Age (LSA). These sites have provided some of the earliest evidence for complex human behaviour and technology during the MSA. We used phytoliths¿amorphous silica particles that are deposited in cells of plants¿as a proxy for the reconstruction of past human plant foraging strategies on the south coast of South Africa during the Middle and Late Pleistocene, emphasizing the use and control of fire as well as other possible plant uses. We analysed sediment samples from the different occupation periods at the rock shelter Pinnacle Point 5-6 North (PP5-6N). We also present an overview of the taphonomic processes affecting phytolith preservation in this site that will be critical to conduct a more reliable interpretation of the original plant use in the rock shelter. Our study reports the first evidence of the intentional gathering and introduction into living areas of plants from the Restionaceae family by MSA hunter-gatherers inhabiting the south coast of South Africa. We suggest that humans inhabiting Pinnacle Point during short-term occupation events during Marine Isotope Stage (MIS) 5 built fast fires using mainly grasses with some wood from trees and/or shrubs for specific purposes, perhaps for shellfish cooking. With the onset of MIS 4 we observed a change in the plant gathering strategies towards the intentional and intensive exploitation of dry wood to improve, we hypothesise, combustion for heating silcrete. This human behaviour is associated with changes in stone tool technology, site occupation intensity and climate change

Synthesis and Characterization of Ethylenedithio-MPTTF-PTM Radical Dyad as a Potential Neutral Radical Conductor

During the last years there has been a high interest in the development of new purely-organic single-component conductors. Very recently, we have reported a new neutral radical conductor based on the perchlorotriphenylmethyl (PTM) radical moiety linked to a monopyrrolotetrathiafulvalene (MPTTF) unit by a π-conjugated bridge (1) that behaves as a semiconductor under high pressure. With the aim of developing a new material with improved conducting properties, we have designed and synthesized the radical dyad 2 which was functionalized with an ethylenedithio (EDT) group in order to improve the intermolecular interactions of the tetrathiafulvalene (TTF) subunits. The physical properties of the new radical dyad 2 were studied in detail in solution to further analyze its electronic structure.This work was supported by the EU ITN iSwitch 642196 and “Nano2Fun” 607721 DGI grant (BeWell; CTQ2013-40480-R), the Networking Research Center on Bioengineering, Biomaterials, and Nanomedicine (CIBER-BBN), and the Generalitat de Catalunya (grant 2014-SGR-17). ICMAB acknowledges support from the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV-2015-0496). In Denmark, this work was supported by the Danish Council for Independent Research | Natural Sciences (#11-106744). M.S. is grateful to Spanish Ministerio de Educación, Cultura y Deporte for a FPU grant. We thank Vega Lloveras for ESR spectroscopy and Amable Bernabé for MALDI spectroscopy.Peer reviewe

Early evidence of fire in south-western Europe: the Acheulean site of Gruta da Aroeira (Torres Novas, Portugal)

The site of Gruta da Aroeira (Torres Novas, Portugal), with evidence of human occupancy dating to ca. 400 ka (Marine Isotope Stage 11), is one of the very few Middle Pleistocene localities to have provided a fossil hominin cranium associated with Acheulean bifaces in a cave context. The multi-analytic study reported here of the by-products of burning recorded in layer X suggests the presence of anthropogenic fires at the site, among the oldest such evidence in south-western Europe. The burnt material consists of bone, charcoal and, possibly, quartzite cobbles. These finds were made in a small area of the cave and in two separate occupation horizons. Our results add to our still-limited knowledge about the controlled use of fire in the Lower Palaeolithic and contribute to ongoing debates on the behavioural complexity of the Acheulean of Europe.Financial support for the archaeological fieldwork undertaken at the Almonda karst sites was provided by the Municipality of Torres Novas and by projects PTDC/HIS-ARQ/098164/2008 and PTDC/HAR-ARQ/30413/2017, funded by FCT (Fundação para a Ciência e a Tecnologia, Portugal). This study was supported by the Governments of Spain—projects HAR2017-86509 and PGC2018-093925-B-C33 (MCI/AEI/FEDER, UE), Catalonia—project 2017SGR-00011- and France—the International Research Network (IRN 0871 CNRS-INEE): Taphonomy European Network (TaphEN). M. Sanz and J. Daura were supported by Juan de la Cierva (IJCI-2017–33908) and Ramon y Cajal (RYC-2015–17667) postdoctoral grants, respectively. Á. Carrancho gratefully acknowledges financial support from the Junta de Castilla y León (project BU235P18) as well as FEDER funding and project AEI/10.13039/501100011033

Modern soil phytolith assemblages used as proxies for paleoscape reconstruction on the South Coast of South Africa

South Africa continues to receive substantial attention from scholars researching modern human origins. The importance of this region lies in the many caves and rock shelters containing well preserved evidence of human activity, cultural material complexity and a growing number of early modern human fossils dating to the Middle Stone Age (MSA). South Africa also hosts the world's smallest floral kingdom, now called the Greater Cape Floristic Region (GCFR), with high species richness and endemism. In paleoanthropological research, improving our capacity to reconstruct past climatic and environmental conditions can help us to shed light on survival strategies of hunter-gatherers. To do this, one must use actualistic studies of modern assemblages from extant habitats to develop analogies for the past and improve paleoenvironmental reconstructions. Here, we present a phytolith study of modern surface soil samples from different GCFR vegetation types of the south coast of South Africa. In this study, the phytolith concentration and morphological distribution are related to the physicochemical properties of soils, the environmental conditions and the characterization of the vegetation for the different study areas. Our results show that phytolith concentration relates mostly to vegetation types and the dominant vegetation rather than to the type of soils. More abundant phytoliths from Restionaceae and woody/shrubby vegetation are also noted from fynbos vegetation and grass phytoliths are a recurrent component in all the vegetation types in spite of being a minor component in the modern vegetation. The grass silica short cells from these plants, however, suggest a mix of C3 and C4 grasses in most of the vegetation types with a major presence of the rondels ascribed to C3 grasses. The exceptions are riparian, coastal thicket and coastal forest vegetation, which are characterized by the dominance of C4 grass phytoliths

Atlantic overturning in decline?

Global ocean circulation is an important factor in climate variability and change. In particular, changes in the strength of the Atlantic meridional overturning circulation (AMOC) have been implicated in ancient climate events, as well as in recent climate anomalies such as the rapid warming of the North Atlantic Ocean in the mid-1990s. A series of moored current meters and temperature sensors deployed in the Atlantic at 26° N known as the RAPID-MOCHA array has been used to monitor the strength of meridional overturning since 2004. The data indicate a decline in this strength over the period 2004–20123. Here, using additional observations and climate model simulations we suggest that this measured decline is not merely a short-term fluctuation, but is part of a substantial reduction in meridional overturning occurring on a decadal timescale

A new chronological framework and site formation history for Cova del Gegant (Barcelona): Implications for Neanderthal and Anatomically Modern Human occupation of NE Iberian Peninsula

The chronological framework for Neanderthal occupation and demise across Europe continues to be debated. In particular, there is still uncertainty regarding the nature, timing and regional expressions of the Middle to Upper Palaeolithic transition associated with the disappearance of Neanderthals and the broader expansion of modern human populations in Europe around 42e40 thousand years ago (ka). The geographical and chronological distribution of Neanderthal populations also remains difficult to evaluate owing to the practical challenges of directly dating human fossils at many sites, and the fact that a large proportion of Neanderthals sites lie close to, or well-beyond, the limits of radiocarbon dating. Cova del Gegant e one of the few sites in north-eastern Iberian Peninsula to yield Neanderthal fossil remains, associated Mousterian archaeological layers, and occupations related to the Middle and Upper Palaeolithic transition e is a key locality for informing these ongoing debates. Here we provide a comprehensive chronological framework for the Cova del Gegant site using multiple radiometric dating techniques (uranium-thorium (UeTh), radiocarbon and luminescence dating), sedimentological and micromorphological analyses, and Bayesian modelling. This integrated chronostratigraphic approach enables us to reliably reconstruct site formation processes and history, and undertake improved correlations with other sites regionally. The results allow us to sub-divide the Cova del Gegant sequence into three sections spanning ~94 ka to ~32 ka, namely: a Middle Palaeolithic sequence covering ~94e59 ka, a Châtelperronian/Aurignacian section spanning ~43e39 ka, and a Late Aurignacian/Gravettian section spanning ~34e32 ka. The Neanderthal fossil remains accumulated in the cave between the end of Marine Isotope Stage (MIS) 5/MIS 4 and the beginning of MIS 3, during two different events dated to ~72e67 ka and ~60e52 ka. The chronological framework for Cova del Gegant is in accordance with that reported for other Middle and Upper Palaeolithic sites in north-eastern Iberian Peninsula, and reveals a record of successive human occupation coinciding with a period of progressive global cooling and lowering sea levels (end of MIS 5 through to MIS 2). Sedimentological evidence points to the emergence of a coastal platform in front of the cave and indicates that local palaeoenvironmental conditions likely benefited human displacements along the littoral margin, and favoured repeated occupation of the cave during the Late Pleistocene

The Mas del Pepet experimental programme for the study of prehistoric livestock practices: Preliminary data from dung burning

The research for referential data on current livestock contexts is essential for correctly interpreting archaeological records documented in prehistoric livestock spaces. Experimental programmes such as the one begun in 2014 in the Mas del Pepet pen (Rojals, Tarragona) has permitted an understanding, among other matters, of fold characteristics according to the type of livestock, the seasonality of occupations and herd management. This study also contributes to the identification of taphonomic processes that have taken place and to determine the representativeness of the botanical content in the deposit, in relation to the environment and pasture areas. Finally, the dung burning experiments conducted have provided data that will help to reveal the way manure was treated in prehistoric fold caves.MINECO project (CGL2012- 38434-C0303) and the Generalitat de Catalunya (2014SGR900; 2014SGR899