The use of wood in funerary pyres: random gathering or special selection of species? Case study of three necropolises from Poland

In this study, the analysis of charcoal remains from three prehistoric necropolises is presented. This botanical material formed part of funerary pyres and thus represents purposely gathered wood used for cremation ceremonies. Therefore, its anthracological analysis may indicate a special selection of wood, which may be a source of palaeoethnographic information about past rituals. However, a question remains as to whether or not the charcoal assemblages that originated from graves may also provide some palaeoecological information. In order to test both hypotheses, analysis of three Polish necropolises dating to the Bronze and the Iron Age were performed. In all charcoal assemblages, a taxonomic diversity among charcoals was detected, which may suggest that the wood was collected based on availability. This may also be inferred after observing that the presence of the most ubiquitous and frequently found taxa may be strongly correlated with present-day vegetation growing in the vicinity of the necropolises.     

Preservation potential of charcoal in alkaline environments: an experimental approach and implications for the archaeological record

Charcoalified plant material (usually wood) has been described as being inert with a high preservation potential. Although usually black on both the outside and inside, the physical and chemical properties differ as a function of temperature and time of exposure to a heat source. Post-depositional processes however may exert additional affects on charcoalified material and introduce bias into the archaeological record. This work explores the influence of alkaline conditions, often encountered in the soil environment, on the preservation potential of charcoalified material. Charcoal, experimentally produced at different temperatures, was exposed to a number of solutions of potassium hydroxide and calcium hydroxide with different pHs, to simulate exposure to alkaline soil conditions. Under these conditions chemically mediated physical interactions occur resulting in fragmentation of the charcoal samples into (very) small pieces the size of which depends upon the initial temperature of charcoalification. Moreover further interactions result in a decrease in reflectance relative to samples not exposed to alkaline conditions. Although experimentally driven the potential for physical loss of charcoal from a particular site coupled with the reduction in (expected) reflectance of any resident material, has important implications for any conclusions drawn regarding the archaeological record.     

Modeling wood acquisition strategies from archaeological charcoal remains

Archaeological charcoal remains are often used to reconstruct local woodland composition in the past, but rarely address how and why people may have selected specific woody taxa for particular purposes. Models from the field of human behavioral ecology predict that people forage for wood resources by taking into account the relative usefulness, abundance, and handling time related to procuring different wood types. Archaeological and ecological data from the site of Gordion, in Central Anatolia (modern Turkey), were used to test expectations associated with such models. Results suggest that inhabitants of Gordion used wood types for fuel in proportion to their local availability, but that they selected specific, more distant woods for construction. In most occupation periods pine was preferred for construction, perhaps because it produces long, straight timbers for roofing, despite the distance at which it grows from the site. This case study demonstrates that behavioral ecology modeling can help to distinguish between multiple wood acquisition strategies potentially used in the past and improve our understanding of wood use from archaeological charcoal remains.     

Fire and ritual: bark hearths in South-American Tupiguarani mortuary rites

High proportions of bark pieces (up to 85% of the charcoal content) were found in several hearths from Morro Grande archaeological site (Southeastern Brazil). This site, dated between 3220–2840 and 1820–1390 yrs cal BP, is associated to the Tupiguarani Tradition, attributed to supposed ancestors of Tupinambá native populations, who occupied the major part of the Brazilian coast in the XVIth century. Bark hearths, archaeologically associated with the mortuary ritual, were found encircling a funerary urn and associated with ceramic fragments painted with elaborated patterns in black, white, and red. Other hearths, spatially isolated from the funerary area, were associated to fragments of utilitarian non-painted ceramics and therefore attributed to domestic contexts. These ones presented few or no bark fragments. It is clear that bark was intentionally selected as fuel for the funerary hearths. Although bark is related, in historic accounts, as a specialized firewood for ceramics firing, its presence in ritual context has not been previously recorded. In this paper, the anthracological record is discussed in the light of ethnographic and historic accounts. A possible explanation for the presence of bark hearths in funerary context is proposed, suggesting it might be a symbolic parallel with the quotidian: the potency and power of transformation of bark as a fuel would be regarded in a spiritual level, achieving the transformation of the body soul in the revered soul – an Ancestor.     

The phytolith archaeological record: strengths and weaknesses evaluated based on a quantitative modern reference collection from Greece

The phytolith record from archaeological strata is a powerful tool for reconstructing aspects of past human behaviour and ecology. Considerable insights into the problems and potentials of this record can be obtained by studying phytoliths in modern plants. We prepared a phytolith reference collection of modern plants mostly from northern Greece that includes quantitative information on phytolith concentrations (number of phytoliths per gram dry organic material) and morphological assemblages. Here we analyse this reference collection with the aim of evaluating the strengths and weaknesses of the archaeological phytolith record. The reference collection comprises 62 different plant taxa. Of them, 28 are trees, 1 conifer, 10 shrubs and 1 herb, 3 domesticated annual legumes and 19 monocotyledons. We demonstrate quantitatively the extent to which woody species, legumes and fruits of dicots contribute only small amounts of phytoliths to the sediments per unit tissue dry weight, while leaves of trees and shrubs produce significant amounts of phytoliths and grasses are prolific phytolith producers. We compare the data of this reference collection with a similar reference collection from another Mediterranean ecosystem (Israel). The comparison indicates that some aspects of phytolith production are probably genetically controlled, whereas others are environmentally controlled. We note that despite the fact that woody species produce few phytoliths per gram of tissue, their record can be most informative when taking into account other properties of the sediments. We also note that jigsaw puzzle-shaped phytoliths normally form in plants that grow in humid conditions, but may form in arid environments when the plants are irrigated. This study clearly shows the extent to which some plants can be under-represented and others over-represented in the phytolith record. Knowing the extent of this bias can greatly improve our interpretation of the phytolith record.     

The use of forest resources in central Iberia during the Late Iron Age. Insights from the wood charcoal analysis of Pintia,a Vaccaean oppidum

Charred woods may be used to effectively reconstruct past wood acquisition strategies. We used anthracological data from the pre-Roman settlement of Pintia (Padilla de Duero, Valladolid) to examine the use of forest resources at the local scale. Palaeoecological data revealed heterogeneous landscapes in the inland northern meseta with environments that offered diverse sources of wood for the inhabitants of Pintia, one of the first cities of inland Iberia. Pines (Pinus pinea/pinaster and Pinus sylvestris/nigra) and both evergreen and deciduous Quercus L. and Juniperus L. were the main taxa identified as both fuelwood and construction elements, but the assemblages and frequencies of these taxa differed depending on their use. We also examined the potential of models from human ecology by considering the frequency, handling time and the relative technological value of each taxon to model how people gathered wood resources. The results suggest that although local availability affected the forest resources that were used by the Vaccaei people, specific taxa were positively selected for specific uses.     

An investigation of climatic change in the holocene epoch using archaeological charcoal from Swaziland, Southern Africa

A methodology is described for the analysis of Holocene charcoals excavated from a rock shelter in the Lubombo Mountains of northeast Swaziland. Scanning electron microscopy was used to compare these with modern reference woods. Of the ancient material 96·6% could be identified, in some cases at specific level. It is in such a subtropical area, where the woody flora is so rich, that assemblages of local taxa can be used in palaeoclimatic reconstructions. The changing taxa indicated by the charcoal fragments from the rock shelter clearly reflect minor shifts in Holocene climate, from moist to dry and back to moist in recent times. This is of relevance to the fluctuations in Stone Age populations in southern Africa. The wider use of such evidence to complement other palaeoenvironmental and archaeological data is advocated.     

Fuel, Fire and Heat: an experimental approach to highlight the potential of studying ash and char remains from archaeological contexts

As in traditional societies today ancient societies probably selected different fuels to meet specific heat requirements. Char and ash, the end products of fire, are often found in abundance in archaeological contexts. These end products can provide information regarding (i) the original fuel resource and type, (ii) the characteristics of the fire and (iii) combined with other archaeological evidence shed further light on possible socio-economic activity(-ies) associated with that fire. The three main fuel resources would have been (i) modern vegetation, (ii) fossil fuel and (iii) animal by-products. Local availability and abundance would have influenced the choice made.In this study an experimental approach was adopted to try and distinguish between the three different fuel resources that are known to have been used by ancient societies (and continue to be used by traditional societies today) from their char and ash remains to help determine original fuel-type and understand the relative heating properties. For this end one fuel-type from each fuel resource listed above, namely wood, peat and cow dung, was chosen.     

Morphological,chemical and physical changes during charcoalification of wood and its relevance to archaeological contexts

Wood exposed to a heat source can be transformed into charcoal if subject to conditions of carbonisation (in the absence of air) or charring (in restricted air). Charcoal recovered from archaeological sites can yield fundamental information to our understanding of human economic and cultural development over time and (ecological) setting. This work describes the morphological (anatomy, degree of shrinkage), physical (reflectance) and chemical (elemental, molecular composition) properties of charcoal in relation to heat source and wood variables. In this study charcoal and charcoal fuel were experimentally produced whereby temperature (160–1200 °C), time of exposure (2–1440 min), heating rate (high and low) and wood type (angiosperm and conifer) were varied. The results show that charcoal, often described as an inert, black material, has different chemical and physical properties in relation to the investigated variables. By using these different properties it is possible to distinguish between the different types of fires (domestic and industrial) exploited by humans in the past. Morphological analyses and reflectance measurements are effective tools for this purpose and can be used in wood exposed to temperatures of 300 °C and above—temperatures which are relevant to archaeological research. Angiosperm and conifer wood react in different ways when exposed to heat and thus the taxonomic identity of archaeological material needs to be known. Chemical analyses can be used for wood exposed to temperatures below 400 °C whereas elemental analyses of the carbon content can be used for wood exposed to temperatures up to a maximum of 650 °C.     

Late Holocene human impact on the vegetation around Mizorogaike Pond in northern Kyoto Basin,Japan: a comparison of pollen and charcoal records with archaeological and historical data

Pollen and macroscopic charcoal analyses of AMS radiocarbon-dated sediment from Mizorogaike Pond, located near Japan’s ancient capital established in AD 794, were used along with archaeological and historical data to reconstruct vegetation change in the northern Kyoto Basin since 7300 cal yr B.P. Between ca. 7300 and 3400 cal yr B.P. (Early to Late Jomon period), the site was surrounded by warm-temperate forest composed of Quercus subgenus Lepidobalanus and Q. subgenus Cyclobalanopsis with Celtis/Aphananthe trees. With the occurrence of fire disturbance, Q. subgenus Lepidobalanus increased from ca. 3400 to 1400 cal yr B.P. (Late Jomon to Kofun periods). In the early seventh century (Asuka period), Pinus started to increase, coinciding with a significant charcoal peak, probably related to the operation of roof tile kilns near the site. Pinus continued to increase and Q. subgenus Cyclobalanopsis decreased through the seventh to tenth centuries (Asuka to Heian periods). Further increase of Pinus occurred in the eleventh century, possibly reflecting the establishment of the manor of Kamigamo Shrine. From the eleventh to seventeenth centuries (Heian to medieval periods), no significant vegetational change or fire disturbance took place. In the eighteenth century, the landscape became totally open, with poor vegetation and sparse Pinus woodland. The medieval and early modern landscapes reconstructed from the palaeoecological record are rather similar to those described from studies of ancient artwork and historical documents. This study demonstrates that late Holocene vegetation change in the northern Kyoto Basin was closely tied to anthropogenic activities, such as the pottery industry and fuel wood collection.     

Species identification of archaeological dung remains: A critical review of potential methods

Abstract

Dung, macroscopically recognisable as such or not, can more commonly be found in archaeological contexts than is perhaps realised. Up to now, identification of dung to the species which produced it is usually either tenuous, or is not possible. However, species identification can be very informative and is necessary before any further studies can be conducted on the dung, for example on health and hygiene in the past and palaeoecology. This study presents a review of potential methods by which species identifications of archaeological dung can be undertaken. Criteria for identification can be divided into three broad categories: morphometric features of the dung; the content of dung and contextual evidence. Overall, the chances of a precise identification are high; however, a combination of different criteria and techniques will often be necessary to establish a secure identification. Moreover, preservation issues may exclude the application of some criteria while several criteria require more research and the expansion of reference collections of recent material. The overall aim is to move towards standardised methods for species identification of archaeological dung.     

New trials in the consolidation of waterlogged archaeological wood with different acetone-carried products

Some acetone-carried consolidants for waterlogged archaeological wood were tested in order to evaluate treatments able to save time and energy. In details, colophony (rosin), two esterified colophonies (Rosin 100^® and Rosin 459^®), a mixture of colophony with PEG 3400 and a vinyl acetate - vinyl versate copolymer (Vinavil 8020S^®) were tested. The treatments were carried out at temperatures of 20 and 35 °C on waterlogged maritime pine, elm, oak and beech. The materials came from the archaeological site of the ancient ships of Pisa (Tuscany, Italy) and were dated back to VII cent. BC – II cent. AD. To evaluate the processes, equilibrium moisture content and dimensional stability of treated wood samples at different relative humidity, and retention of impregnating products were measured; moreover macroscopic and microscopic examination were also run to respectively assess the shape and appearance of treated wood and the way of deposition of consolidants. The results highlighted that natural and modified colophony treatments gave the most satisfactory results both in the maintenance of shape and dimensions of samples and in the stabilization with respect to RH variations. Moreover, the equilibrium moisture contents of samples treated with R100 and R459 were much reduced in comparison to the other consolidants and to untreated archaeological wood. This fact was related to the high retention values of those products that occluded most of the porosity including the microporosity of cell walls. Therefore, in terms of higroscopicity treated wood was more similar to impregnating substances rather than to decayed wood. This fact was considered helpful in contrasting the moisture-related negative effects in cases of eventual faults in the climate control during e.g. exhibition and in protecting treated wood from the risks of new fungal attacks.     

Starch grain characterization of Prosopis chilensis (Mol.) Stuntz and P. flexuosa DC,and the analysis of their archaeological remains in Andean South America

The fruit (pods) of Prosopis (Fabaceae) are frequently recovered from pre-Hispanic Argentinian archaeological sites, suggesting that this genus was of importance in ancient economies in this region. Yet it is only recently that archaeobotanists have begun to carry out systematic research into this genus. Therefore many questions remain to be addressed concerning the food value of Prosopis fruit, and its potential contribution. This paper examines starch from the pods of two species, Prosopis flexuosa and Prosopis chilensis, for the purposes of describing and classifying their morphological features and biometrical parameters. Pods of both species were gathered from two extremes (northern and southern) of the Hualfín Valley, Catamarca, Argentina. Starch abundance is estimated and compared with that of Zea mays, an economically important plant with high concentrations of starch. This paper reveals that Prosopis pods contain very low amounts of starch compared to starch-rich edible species. Despite this, the recovery of Prosopis starch grains can be successfully used to assess archaeological tool uses. Prosopis starch grains were found to be highly variable in shape. Grain size ranged between 10 and 20 μm. Granule irregularity and the high birefringence under polarized light are two of the most important diagnostic features. No significant statistical differences were found in the structure (morphology, size and hilum) of the starch of the same species from both localities. Finally, the implications for the role of this plant in past societies are discussed.     

Study of interactions between polyethylene glycol and archaeological wood components by C high-resolution solid-state CP-MAS NMR

While use of polyethylene glycols, PEG, polymers for archaeological wood conservation has been well established, there is almost no study of such composite materials with carbon thirteen high-resolution solid-sate NMR. We demonstrate that NMR is an useful analytical tool to characterize rapidly samples of conserved wooden objects. By choosing an appropriate value of the contact time (from 3 to 5 ms) for which the PEG component gives only a small residual NMR signal in the CP-MAS experiment, it is possible to edit selectively the spectra of the wood components. It allows one to visualize the degradation extent of the archaeological wood even when the conservation processes have been already applied. Moreover, by studying the kinetics of CP-MAS experiments, the time constants, T_1ρH and T_CH values for PEG moiety were computed. From these data, it is shown that either in the crude commercial product or in incorporated in archaeological woods, two components are present and they are the signatures of crystalline (or ordered) and amorphous (or disordered) molecular domains. Moreover, it was shown in the archaeological woods that almost 30% of PEG was in close molecular interactions with lignins. This study is the first evidence that the PEG in conserved wood can interact at a molecular level with wood components. It also demonstrates that the PEG diffuses inside the residual cell walls of archaeological wood. This data are important for scientists in charge of process development for the conservation of wooden artifacts.     

Alkali extraction of archaeological and geological charcoal: evidence for diagenetic degradation and formation of humic acids

Charcoal forms a crucial source of archaeological and palaeoenvironmental data, providing a record of cultural activities, past climatic conditions and a means of chronological control via radiocarbon (¹⁴C) dating. Key to this is the perceived resistance of charcoal to post-depositional alteration, however recent research has highlighted the possibility for alteration and degradation of charcoal in the environment. An important aspect of such diagenesis is the potential for addition of exogenous “humic acids’ (HAs), to affect the accuracy of archaeological and palaeoenvironmental reconstructions based upon chemical analyses of HA-containing charcoal. However the release of significant quantities of HA from apparently pristine charcoals raises the question whether some HA could be derived via diagenetic alteration of charcoal itself. Here we address this question through comparison of freshly produced charcoal with samples from archaeological and geological sites exposed to environmental conditions for millennia using elemental (C/H/O) and isotopic (δ¹³C) measurements, Fourier Transform Infrared Spectroscopy (FTIR) and proton Liquid-State Nuclear Magnetic Resonance (¹H NMR). The results of analyses show that the presence of highly carboxylated and aromatic alkali-extractable HA in charcoal from depositional environments can often be attributable to the effects of post-depositional processes, and that these substances can represent the products of post-depositional diagenetic alteration in charcoal.     

Stable carbon and oxygen isotopic compositions of wood ash: an experimental study with archaeological implications

Wood ash, composed mainly of the mineral calcite, is an important component in many archaeological sites. Identification of wood ash in the archaeological record is often difficult due to mixing of ash with other calcitic components of geogenic origin and/or due to diagenetic changes. A recent empirical study using the stable isotope compositions of carbon (δ¹³C) and oxygen (δ¹⁸O) in wood ash enabled the identification of mixtures of wood ash with geogenic calcite and to follow diagenetic changes due to partial dissolution and re-precipitation of ash in two prehistoric cave sites in Israel. Little however is known about the processes responsible for the isotopic compositions of wood ash in relation to formation at various temperatures and the influence on isotopic composition of ash from a variety of plant species. Here we present an experimental study of wood ash formed by burning three C3 tree species and one C4 desert bush at different temperatures. The results indicate that there are significant differences in the isotopic compositions of carbon and oxygen between wood ash that forms by combustion at a relatively low temperature (500 °C) and at a higher temperature (900 °C). In addition, we show that the isotopic composition of carbon and oxygen in high temperature wood ash approaches equilibrium over a period of several months and that the carbon isotopic composition of low temperature wood ash may reflect the photosynthetic pathway of the burnt woody species. Lastly, we show that the isotopic compositions obtained from wood ash prepared at different temperatures do not reflect a temperature dependent fractionation process, but a mixing line between calcite that formed by low temperature combustion and calcite formed by high temperature combustion which later underwent re-carbonation with atmospheric CO₂. In addition, we suggest that exchange processes may possibly occur during combustion between decomposing calcium-oxalate and atmospheric O₂, CO₂ and CO. The archaeological implications of this study are discussed in relation to identification of wood ash in the archaeological record, identification of fuel sources and burning temperatures, and diagenetic changes expected in karstic cave environments. The method presented here can be applied at any archaeological site.     

Reasoned use of chemical parameters for the diagnostic evaluation of the state of preservation of waterlogged archaeological wood

Waterlogged archaeological wood undergoes decay processes that depend on both the burial conditions and the constituting species, and which cause the depletion of the structural components of wood cells. To quantitatively assess the state of preservation of the decayed material, specific parameters are usually measured by means of both chemical and physical analyses. In this paper an innovative approach in the use of the data obtained from these kinds of measurements is developed. A series of 132 archaeological wood samples of different wood species, burial times and states of preservation, and coming from different sites in Italy, was analysed. Their residual chemical composition, maximum water content and basic density were measured, and a reasoned use of these parameters was carried out through their elaboration, with the aim of both evaluating eventual incongruence or anomalies in the raw physical and chemical data (which has never been accomplished so far) and directly comparing in a reliable way the analytical results obtained from archaeological samples with very different states of preservation. This approach allowed defining the effective values of chemical parameters related to wood decay according to a same reference basis of calculation among the various data. By this way, it was possible to state that lignin can be also attacked by the agents causing biotic decay, and that in hardwoods its decay is more related to the burial conditions than to the wood species. Instead, the mechanism of polysaccharide depletion is diversified: conifers showed a uniform behaviour whereas hardwoods were more species-dependent. Moreover, in addition to the chemical composition, also anatomical factors influence the carbohydrate rate of decay in waterlogged wood.     

Selected physical parameters to characterize the state of preservation of waterlogged archaeological wood: a practical guide for their determination

Non-destructive and destructive methods for determining the physical parameters of waterlogged wood such as the porosity, the water content, the wet and dry bulk densities plus the density of the cell wall material are presented. Considerations in respect to determination of masses, volumes and sampling size are discussed.     

Preservation,storage and display of waterlogged wood and wrecks in an aquarium: “Project Aquarius”

A test aquarium containing water and waterlogged historical wooden material was observed during a three-year period at Vänernmuseum, Sweden, to test the feasibility of preserving and exhibiting archaeological wood or shipwrecks in a way accessible to the public. Experiments were also set up in a laboratory environment, to provide information on single factors that could influence the long-term preservation state of wood, and other processes that may occur in the water.     

Fruit stones from Tiao Lei's tomb of Jiangxi in China,and their palaeoethnobotanical significance

Fruit stones were discovered in Mr. Tiao Lei's Tomb (around 300 AD) at Nanchang, China. The morphology and anatomy of the fruit stones were investigated. They are identified as belonging to three species, namely, Chinese plum (Prunus salicina Lindley), red bayberry (Myrica rubra Sieb. et Zucc.), and Chinese date (Ziziphus jujuba Mill.). These stones suggest the possibility of orchards in the local area, and the fresh or processed drupes of these three species probably played important roles in the tomb owner's life.