Stability of phytoliths in the archaeological record: a dissolution study of modern and fossil phytoliths

Opaline phytoliths are important microfossils used in archaeological and ecological research. Relatively little is known about the stability of phytoliths after burial. Under alkaline pH conditions they can dissolve, and mechanical disturbances can cause a loss of their more delicate appendages. Here we present an experimental study of phytolith stability (combination of solubility and abrasion). Modern and fossil phytoliths were extracted from wheat using new methods to minimize dissolution, and by burning in an oven. These assemblages were placed in a solution buffered to pH 10 and maintained under constant temperature and shaking conditions. The silicon concentrations in the solution were monitored once a week for 5 weeks. The phytolith morphologies in each assemblage were determined at the outset of the experiment and after 5 weeks. The results show that there are differences in stability between various assemblages. Modern inflorescence wheat phytolith assemblages are more unstable than those from leaves/stems. Burnt assemblages are less stable than unburnt assemblages, and a fossil phytolith assemblage about 3000 years old is more stable than the modern wheat assemblages. The results also show that individual phytolith morphotypes have different stabilities, and as a result of dissolution and abrasion, some morphotypes may resemble others. This study further shows that archaeological and/or paleo-environmental interpretation of phytolith assemblages may change with the assemblage’s state of preservation.     

Was it the deer or the fox?

Herbivores, as taphonomic agents, can modify and consume bones and antlers for no nutritive purpose. This unusual behavior is due to a nutritional dysfunction (osteophagia) that allows them to supplement a lack of minerals in their diet through ingestion of minerals contained in bones. When chewing, herbivores change skeletal element morphology and produce a characteristic forked shape. At an incipient stage of modification, herbivore chewing may mimic that of carnivores. In this paper, we provide diagnostic criteria to distinguish bone modification made by herbivores from that produced by other taphonomic agents, mainly carnivores.     

Human soft tissue preservation in the Cova des Pas site (Minorca Bronze Age)

The preservation process of soft tissues in an archeological context is mainly unknown because they occur only in truly exceptional situations. The Cova des Pas is a Bronze Age site in Minorca where the special conditions enabled the preservation of some soft tissues associated with 66 individuals. This finding allows the study of the preservation process that took place by means of the analysis of the histological and chemical characteristics of the tissues. Our results show that the preservation mechanism was the adipocere, because the fatty acids profile shows higher concentration of saturated than unsaturated fatty acids. The evidence indicates that the kind of funerary ritual and the environmental conditions favored this preservation.     

Rock type variability and impact fracture formation: working towards a more robust macrofracture method

Investigations into the development of weapon systems are increasingly important in archaeological debates about human evolution and behavioural variability. ‘Diagnostic’ impact fractures are key, but controversial, lines of evidence commonly used in such investigations. In 2009 a series of experiments was initiated to investigate the processes associated with macrofracture formation specifically focussing on the taphonomic factors affecting the formation of ‘diagnostic’ impact fractures (DIFs). This paper adds to that experimental data set with macrofracture results from recent knapping experiments investigating rock type variability and DIF formation. These results show that rock type variation plays less of a role in DIF formation than variables related to use and lithic taphonomy. The collective results of this experimental series show that the location, co-occurrence, type and proximity to retouch on a tool are all important means of distinguishing between weapon and non-weapon related DIFs. Collectively these macrofracture patterns are more important in diagnosing weapon components than any one ‘diagnostic’ impact fracture is alone. Overall, these experimental studies are showing that background ‘noise’ in the form of non-hunting related impact fractures, exists in many macrofracture results and that much work remains in securing the analytical robusticity of the method. The paper concludes that the macrofracture method is not a stand-alone method, but when used with caution and in conjunction with other lines of evidence it is a useful, time-efficient, tool for generating assemblage-level use-trace data.     

Avian Remains from Khonkho Wankane,an Urban and Ceremonial Center in the Southern Lake Titicaca Altiplano

The urban and ceremonial center Khonkho Wankane flourished in the southern Lake Titicaca Altiplano region during the Late Formative prior to the rise of Tiwanaku as a dominant urban center. This site yielded an avifaunal number of identified specimens (NISP) = 631, with a minimum of 26 taxa represented among 539 skeletal elements or fragments. A total of 92 egg shell fragments also were recovered. The avifauna inhabited two major ecological zones: Lake Titicaca, its margins/wetlands and other water margins; and the dry Altiplano grassland (or puna). Lake/wetland taxa include Phoenicopterus chilensis (Chilean flamingo), Nycticorax nycticorax (night heron) and multiple taxa in the Order Anseriformes (ducks, geese, etc.) including Chloephaga melanoptera (Andean goose), Anas georgica (yellow‐billed pintail), A. flavirostris (speckled teal) and Oxyura jamaicensis (Andean ruddyduck). Also present are Fulica ardesiaca (Andean coot), Gallinago andina (puna snipe), Himantopus mexicanus (black‐necked stilt) and Charadrius alticola (puna plover). Puna taxa include Nothoprocta cf. ornata (ornate tinamou), Nothura cf. darwinii (Darwin's nothura), Metropelia sp. (ground doves), Athene cunicularia (burrowing owl), and multiple Passeriformes (songbirds, etc.). Taxa with a cosmopolitan distribution include Falco cf. femoralis (aplomado falcon) and Tyto alba (barn owl). Taphonomic analysis indicates that the avifauna were used in ceremonial contexts, including multiple Falco cf. femoralis burials, and for dietary and possibly tool‐making purposes. Other sources of introduction into the site deposits likely include natural mortality of taxa directly inhabiting the site area. These findings are compared to the avifauna recovered from the Formative site of Chiripa along the Lake Titicaca margin, which included a much higher proportion of lake bird fauna. At Khonkho Wankane, the importance of wetland avifauna may have been enhanced by the alteration of the local environment to include qochas, or artificial reservoirs/ponds, and continued despite reliance upon multiple domesticated plant and mammal species. Copyright © 2011 John Wiley & Sons, Ltd.     

Cut marks on the Middle Pleistocene elephant carcass of Áridos 2 (Madrid,Spain)

Áridos 1 and Áridos 2 (Madrid, Spain) are two Middle Pleistocene sites belonging to the isotopic stages 9–11. Both places contain partial carcasses of Elephas (Paleoxodon) antiquus associated to Acheulian stone tools. In this work, the taphonomic study of the elephant remains of Áridos 2 is presented. This study has documented several cut marks on different bones, which indicate bulk flesh and viscerae extraction by Middle Pleistocene hominins. Several arguments are provided to support that at least some of the cut marks were made with handaxes, further suggesting that some of these artifacts were butchering tools in this stage of human evolution. Although cut marks on elephant carcasses have been documented at some Middle Pleistocene sites, very few have been published in detail to allow consideration of their status as hominin-imparted marks. By doing so, the present study provides more evidence of large carcass exploitation by hominins during this period.     

Bone survival: The effects of sedimentary abrasion and trampling on fresh and cooked bone

It is commonly assumed that, at least when considering similar sized animals, the bones from all taxa stand an equal chance of preservation. This paper summarizes one aspect of a larger study undertaken in order to assess whether this assumption is true, based on the results of experiments and observations into the effects of a range of pre-depositional processes. The rates of bone destruction by sedimentary abrasion and by trampling are determined for small mammal, fish and frog bones. Patterns of bone loss and fragmentation are examined both between species and within the skeleton, for fresh and boiled bone. It is shown that there is considerable interspecies variation in the ability of bones to withstand these physical forces. Frog bone proved particularly resistant, while within the fish, bone from the Gadidae was less resilient than might be expected, given its predominance in British Medieval archaeological sites and coastal sites of all periods. Within the skeleton, bone shape appears to be a very important determinant of relative survival. Boiling dramatically reduces bone's resistence to destruction. The physical properties of fresh, boiled and burnt bone are compared mechanically, and the dramatic loss of strength induced by heating is demonstrated. The often voiced assumption that fish bone is more prone to destruction than mammal bone is shown to have some validity. The results add more evidence to support the view that comparison of species abundance by fragment counts may not always be appropriate, and that interpretation of skeletal element frequencies should be approached with caution.     

Experimental assessment of maize phytolith and starch taphonomy in carbonized cooking residues

Many taphonomic studies of plant microfossils, specifically phytoliths and starch, are concerned with post-depositional movement, contamination, and morphological changes due to environmental fluctuations or plant processing. Additionally, the identification of phytoliths and starches archaeologically are based on their presence or absence. This paper examines whether it is possible to identify maize (Zea mays ssp. mays) phytolith and starch abundance associated with different processing behaviors as replicated through experimentally produced cooking residues. If successful, identification of likely associated processing and taphonomy of these microfossils will allow for a more refined interpretation of plant use as it relates to timing and plant form and processing.     

Who brought in the rabbits? Taphonomical analysis of Mousterian and Solutrean leporid accumulations from Gruta do Caldeirão (Tomar,Portugal)

In the Iberian Peninsula, leporids, and specifically rabbits, play a key role in the understanding of hunter-gatherer economies. They appear to have been especially important in the Tardiglacial, when large numbers of small prey animals and of the European rabbit (Oryctolagus cuniculus) in particular, are a ubiquitous feature of faunal assemblages from archaeological sites. Since a large number of non-human predators can also contribute to the formation of such assemblages, the ability to discriminate between bones accumulated by humans and by other kinds of predators is a key prerequisite to their interpretation. On the basis of systematic actualistic studies carried out on modern leporid remains produced by mammalian terrestrial carnivores, nocturnal and diurnal raptors, and humans, we identified diagnostic taphonomic indicators of the different predators. In this paper, the patterns observed on the modern material are applied to the taphonomical analysis of two archaeological samples of rabbit and hare remains from Mousterian and Solutrean layers of Gruta do Caldeirão, a cave site located in Central Portugal. Our results suggest that Eagle Owl (Bubo bubo) were mainly responsible for the Mousterian accumulations, whilst the Solutrean ones were most likely the result of human activity. These data support the notion that, in Iberia, significant reliance on rabbits does not become a feature of subsistence strategies until later Upper Palaeolithic times.