The measurement of taxonomic evenness in zooarchaeology

Zooarchaeologists frequently measure taxonomic evenness to document subsistence change and to understand the response of faunal communities to paleoenvironmental change. Although the measurement of evenness is commonplace, there are numerous challenges involved. Evenness indices are sensitive to changing richness, and by extension sample size, and various indices respond differently to changing taxonomic abundances (i.e., changing evenness). To refine protocol for comparing assemblages of varied sampling effort and identify indices that may be more useful for zooarchaeological applications, we examine the quantitative behavior of the widely used Shannon evenness and Simpson indices and two others more commonly used by ecologists. These indices are examined in relation to varied richness, sample size, and taxonomic abundances. We show that although zooarchaeologists are concerned with identifying and correcting for the effects of sample size on evenness, it may be appropriate to instead focus on how richness modulates evenness. Based on our analyses, we recommend the Simpson index for most zooarchaeological applications, except when comparing evenness across assemblages that are very even.     

The Impact of recovery methods on taxonomic richness in Roman faunal assemblages

Recovery methods can affect species richness in faunal assemblages, which can in turn impact interpretations of diet. A comparison of sample size to species richness across faunal collections from screened and from unscreened deposits associated with Roman occupations clearly shows these influences. Not surprisingly, the rate of species input was higher for collections recovered using screening methods than for collections not recovered from screens. Syntheses of published data and comparative analyses of faunal assemblages must be cognizant of whether or not included assemblages were recovered using screens.     

Do faunal remains reflect socioeconomic status? An ethnoarchaeological study among Central African farmers in the northern Congo Basin

Zooarchaeological analyses often draw inferences on socioeconomic status from the composition of bone assemblages associated with houses and other structures in residential sites. In this paper, we test how well faunal assemblages reflect socioeconomic differences among contemporary farmer households in two rural villages in the Central African Republic. Independent measures of wealth are tallied and ranked for six households in each village, including complete inventories of the types and numbers of material goods and the sizes of residential structures and agricultural fields. These data are compared against the associated food bones collected from household trash middens and activity areas, including skeletal abundances, large mammal body part representation, and taxonomic diversity. In most instances larger and more taxonomically diverse faunal assemblages are associated with houses of means and the faunas do, in fact, reflect differences in socioeconomic status. However, faunal “wealth” may be linked to factors unrelated to social or economic inequalities, notably the presence of active hunters. Our analyses suggest that small animals provide useful and important data in assessing socioeconomic means, and comparative studies of wealth in archaeological contexts should not be based on bones alone.     

Identifying the Involvement of Multiple Carnivore Taxa with Archaeological Bone Assemblages

Information on the number of carnivore taxa that were involved with archaeological bone assemblages is pertinent to questions of site formation, hominid and carnivore competition for carcasses and the sequence of hominid and carnivore activity at sites. A majority of early archaeological bone assemblages bear evidence that both hominids and carnivores removed flesh and/or marrow from the bones. Whether flesh specialists (felids) or bone-crunchers (hyaenas), or both, fed upon the carcasses is crucial for deciphering the timing of hominid involvement with the assemblages. Here we present an initial attempt to differentiate the tooth mark signature inflicted on bones by a single carnivore species versus multiple carnivore taxa. Quantitative data on carnivore tooth pits, those resembling a tooth crown or a cusp, are presented for two characteristics: the area of the marks in millimetres, and the shape as determined by the ratio of the major axis to the minor axis of the mark. Tooth pits from bones modified by extant East African carnivores and latex impressions of tooth pits from extinct carnivore species are compared to those in the FLK Zinjanthropus bone assemblage. Data on tooth mark shape indicate greater variability in theZinj sample than is exhibited by any individual extant or extinct carnivore species in the comparative sample. Data on tooth mark area demonstrate that bone density is related to the size of marks. Taken together, these data support the inference that felids defleshed bones in the Zinj assemblage and that hyaenas had final access to any grease or tissues that remained.     

What can supraspecies richness tell us?

Biogeographers, ecologists, palaeontologists, and conservation managers often deal with checklists in which not all individuals have been identified to a species level, or the accuracy of species identification is questionable. Is it possible and credible to investigate species richness based on such checklists? Studies on macrofauna in the Far Eastern seas, eastern Arctic seas, and adjacent waters of the Pacific and Arctic Oceans suggest that in different habitats and for diverse taxa, species, and higher taxa richness strongly correlate with each other and increase with an expansion in the study area and sample size according to the species–area law. Such an increase is higher in the bottom zone than in the pelagic. Species and higher taxa richness also show a decrease from lower to higher latitudes, which is in line with the Humboldt–Wallace’s law. According to Willis’ law and self-similarity in the organisation of taxonomic levels, species richness can be assessed based on the genus, family, and order richness. In other words, supraspecies richness itself can tell us the same as species richness and therefore certain global patterns revealed at the species level may also be revealed at the supraspecies level. Such a concordance in general trends among richness parameters at different taxonomic levels in practice implies that species richness can be studied based on lists that lack species identifications or lists with doubtful species identification. We suggest bolder use of supraspecies richness in science and practice, discussing the disadvantages and advantages of this approach.     

Bias in Fish Bone Recovery from Differential Collection Techniques and Its Impact on Cultural Interpretation in California

ABSTRACT

While studies on recovery bias are numerous in the literature, the current research focuses on defining best practices in field collection techniques to provide a more accurate representative of site constituents, particularly fish remains. Methods to determine best practices included use of 1/4-inch, 1/8-inch, and 1/16-inch mesh to process excavated material from 10 × 10?cm and 40 × 40 cm-sized bulk column samples and from a 1 × 1 m test unit. Fish remains were compared to determine density and diversity differences between the samples and how these different data sets may impact cultural interpretations. This research shows that while collection of larger column samples processed using a smaller mesh size provides a more robust data set, the taxonomic richness present in a 1 × 1 m test unit provides complimentary data that are critical to understanding subsistence trends as a whole.     

Pits and pitfalls: taxonomic variability and patterning in tooth mark dimensions

Archaeologists use experimentally derived tooth mark frequencies, locations, and size data to infer (a) the extent of carnivore involvement in the formation and modification of faunal assemblages, (b) the size classes of predators marking those assemblages, and (c) whether hominins accessed fleshy or defleshed carcasses (Blumenschine and Pobiner, 2007; Dominguez-Rodrigo et al., 2007). These inferences are often debated in part because frequency counts can vary widely among observers and because the carnivore taxa for which tooth mark dimensional data are available are limited. This study contributes to the body of actualistic/experimental tooth mark data and presents a methodology for collecting these data. We offer a greatly simplified method that may encourage others to collect and quantify tooth mark dimensions. We present dimensional data from feeding experiments with 16 omnivore and carnivore species of known age and mass, ranging in size from skunks to tigers, significantly expanding the taxonomic and size range of carnivores for which we have tooth pit data. Our results demonstrate considerable, but not complete, overlap in tooth pit dimensions among size, class, and taxon. Tooth mark dimensions on epiphyses and metaphyses were relatively strongly correlated with body mass, whereas diaphyseal tooth marks exhibited the weakest correlation. Human consumption of animal tissue produced tooth marks comparable in size to medium felids and small canids, suggesting the possibility that some tooth marks on Early Stone Age (ESA) faunal assemblages could, as suggested by Oliver (1994), result from small carnivore and/or hominin consumption.     

Small prey hunting technology and zooarchaeological measures of taxonomic diversity and abundance: Ethnoarchaeological evidence from Central African forest foragers

Archaeological analyses of faunal assemblages often rely on rationale derived from the prey choice model to explain temporal and spatial changes in taxonomic measures of diversity and/or abundances. In this paper, we present analyses of ethnoarchaeological observations and bone assemblages created by Central African Bofi and Aka forest foragers which show that different small prey hunting technologies target specific suites of prey and that hunters vary their technological choice depending on their foraging goals. Analysis of ethnoarchaeological bone assemblages produced by the Bofi and Aka shows that variability in target prey can create spatially distinct, but contemporaneous, faunal assemblages with different diversity values and abundance indices. These data reveal important variation in how individuals within a contemporary human population rank prey and challenge current assumptions about the meaning of diversity and abundances measures in archaeological contexts. We argue that the use of diversity and abundance indices can obscure important intrasite variability in prehistoric foraging effort and suggest strategies that might enhance current techniques.     

Archaeofaunal Relative Abundance,Sample Size,and Statistical Methods

Tests for correlations between sample size and taxonomic relative abundance are commonly used in zooarchaeological analyses to determine whether observed trends in relative abundance might simply be the result of sampling error. Monte Carlo simulations designed to evaluate the utility of this method indicate that it is inadequate as a means of detecting errors resulting from the incorporation of small samples in an analysis. Among simulated sets of sample assemblages, significant correlatoins between sample size and relative abundance are distributed randomly with respect to whether or not Type II errors concerning trends in relative abundance are present, and are underrepresented in cases in which Type I errors are present. This is because the conditions that are most conducive to correlations between sample size and relative abundance are quite different from the conditions that will lead to erroneous conclusions about the presence or absence of a trend in relative abundance. An alternative chi-square-based statistical method for evaluating trends in sample relative abundance, Cochran's test of linear trend, results in lower rates of both Type I and Type II errors than is the case with previously used correlation-based methods.     

Comment on “Size matters: 3-mm sieves do not increase richness in a fishbone assemblage from Arrawarra I,an Aboriginal Australian shell midden on the mid-north coast of New South Wales,Australia” by Vale and Gargett

In this comment, the author argues that the conclusions reached by Vale and Gargett [Size matters: 3-mm sieves do not increase richness in a fishbone assemblage from Arrawarra I, an Aboriginal Australian shell midden on the mid-north coast of New South Wales, Australia, Journal of Archaeological Science 29 (2002) 57–63] are based on questionable methods and the conclusions regarding the use of fine mesh screens are unsupported.     

Sexual dimorphism in limb bones of ibex (Capra ibex L.): mixture analysis applied to modern and fossil data

Estimating sex ratios of fossil bone assemblages is an important step in the determination of demographic profiles, which are essential for understanding the palaeobiology and palaeoethology of any particular species, as well as its exploitation patterns by humans. This is especially true for ibex (Capra ibex), which was a main source of food for hominids during Pleistocene times. Classical methods for determining sexual dimorphism and sex ratio, such as analyses using uni‐ and bivariate plots, are based on an arbitrary fixing of limits between sexes. Here we use a more robust statistical method termed mixture analysis (MA) to determine the sex of postcranial remains (long bones, metapodials and tarsals) from ibex. For the first time, we apply MA to both a modern and a fossil sample of one species, by using metric data taken from (i) a collection of present‐day ibex skeletons and (ii) a Palaeolithic sample of the same species. Our results clearly show that the forelimb (humerus and radius) is more dimorphic than the hindlimb (femur and tibia) and is therefore better suited for sexing ibex. It also appears that metapodials should be used carefully for estimating sex ratios. On the basis of these results, we propose a classification of bone measurements that are more or less reliable for sexing ibex. The results of MA applied to the ibex fossil bones from the Upper Palaeolithic site of the Observatoire (Monaco) lead us to the conclusion that this assemblage consists of a majority of males. The quantitative estimations calculated by the MA make it possible to compare the size of Pleistocene and modern ibex for the whole set of variables used in this study. Copyright © 2006 John Wiley & Sons, Ltd.     

Exploring Romano–British finds assemblages

This paper presents a synthesis of current approaches to the comparison of archaeological assemblages. It draws its data from Roman Britain but the methodology discussed is equally applicable to other periods and places. Different types of assemblages including those of small finds, broken vessels and animal bones are discussed, and the problems relating to quantification are considered. The different sorts of questions that may be asked of data of varying quality are examined, and it is shown that even 'poor quality' data can provide useful insights into past societies. It is argued that to explore the full richness of the data available, multivariate statistics are an invaluable tool and this is illustrated by exploration of two groups of assemblages using Correspondence Analysis. Finally, attitudes within the archaeological community which may prove a barrier to further advances are examined.     

Oldowan reduction sequences: methodological considerations

Transport of resources is a major feature of Oldowan hominin technological adaptations. Comparisons between different Oldowan localities often employ measures of transport that are based on artefact attributes as proxies for the intensity of raw material utilization. The Technological Flake Category system [Toth, N., 1985. Oldowan reassessed: a close look at early stone artifacts, Journal of Archaeological Science 12, pp. 101–120] has been used extensively to infer the relative intensity of lithic reduction within Oldowan assemblages. Here we use a large experimental sample to test the relationship between a flake's stage in a reduction sequence and various quantitative attributes. We demonstrate how many previously described attributes are affected by initial core size. We then develop a multiple linear regression model that incorporates several variables to predict the placement of a flake within a generalized reduction sequence. The model is then applied to Oldowan assemblages in the Koobi Fora Formation which explores the strengths and weaknesses of different methods of investigating reduction intensity on an assemblage level.     

The Efficiency of Flotation Compared with Other Methods for Recovering Assemblages of Terrestrial and Aquatic Gastropods from Archaeological Deposits,with Reference to the Site of Pico Ramos (Basque Country,Spain)

ABSTRACT

We analysed assemblages of shells of land snails and small aquatic and wetland gastropods from a late Mesolithic-early Neolithic deposit in the cave of Pico Ramos (Basque Country). Shells were recovered by hand during excavation and all excavated deposit was processed by flotation, with a 250 μm mesh to recover floating material and a 1.0 mm mesh to recover the heavy fraction. The total assemblage comprised 5780 individuals (MNI) among 33 taxa, the sieved sub-assemblage having the highest proportions of these (2841 MNI in 31 taxa) and the hand-picked sub-assemblage the lowest (698 MNI in 11 taxa). Eleven taxa were absent from the flotation sub-assemblage, although the recovered MNI (2241; 39% of the total MNI) was high. The palaeoecological implications of the results are considered. Adult and large-sized juvenile shells of the edible land snail Cepaea nemoralis are abundant in the hand-picked sub-assemblage, but it is the absence of small-sized juvenile shells in the flotation and wet-sieved sub-assemblages that permits the inference that the species was collected for consumption. Wet sieving is therefore essential, both for interpreting hand-picked samples and in particular for the recovery of representative assemblages of land molluscs.     

Taphonomic analysis of rodent bone accumulations produced by Geoffroy's cat (Leopardus geoffroyi, Carnivora,Felidae) in Central Argentina

Rodent prey remains recovered from Geoffroy's cat (Leopardus geoffroyi) scats were analyzed in order to identify taphonomic features produced by this predator. The analysis includes a year-long sampling discriminated by the seasons. Modifications produced by digestion are heavy. Taphonomic variables in samples discriminated by the seasons did not show major differences with respect to the total sample; thus, scats collected in any season clearly show the modifications on the bones of prey rodents made by Geoffroy's cats. The results presented here and its interpretation could be extrapolated to an analysis of zooarchaeological or paleontological assemblages.     

Disentangling long bones of foxes (Vulpes vulpes and Alopex lagopus) from arctic archaeological sites

To discern the presence of two anatomically close species within an archaeological assemblage is always a problem for the analyst. A particularly interesting case is the distinction between the red fox (Vulpes vulpes) and the arctic fox (Alopex lagopus), which is often determined using non-rigorous criteria and producing results that must be regarded with caution. Classical methods for separating these two species and determining sexual dimorphism, and eventually the sex ratio, such as analyses using uni- and bivariate plots, are based on arbitrarily fixed limits between sexes. In this text, a more robust statistical method termed mixture analysis (MA) is used to determine the species of limb bones from foxes. First, the MA is applied to a sample of each species using metric data taken from a collection of present-day fox skeletons. Afterwards, the MA is applied to archaeological samples dated to the Dorset period and retrieved from the Tayara site (near Salluit, South Hudson Strait, Nunavik). The results clearly demonstrate that the greatest length (GL) of long bones, especially the humerus and tibia, is the best measurement for distinguishing the species, followed by the distal breadth and the proximal breadth; and that GL is better suited for sexing foxes. The results of MA applied to the Tayara site collection lead to the conclusion that the red fox is present along with the arctic fox among the assemblage, and that there is no fox body size change during the last two millennia in the Eastern Arctic.     

Do temporal size differences influence species identification of archaeological albatross remains when using modern reference samples?

Zooarchaeological remains have been identified to species, using identification criteria based on specific morphological variations among modern specimens. However, temporal size changes in bones, due to micro-evolution and/or phenotypic plasticity, could distort identification of archaeological remains according to these criteria. We developed species identification criteria for North Pacific albatrosses (Short-tailed, Laysan and Black-footed Albatrosses) using both mensural- and DNA-based analysis and actually identified many archaeological remains from a site using these criteria. Our mensural-based criteria could accurately discriminate the modern Short-tailed Albatross from modern Laysan and Black-footed Albatrosses and indicated that the archaeological remains included both Short-tailed and Laysan or Black-footed Albatrosses. DNA-based criteria, however, suggested that all remains were Short-tailed Albatross. The most plausible explanation for this inconsistency would be misidentification using mensural-based analysis, due to temporal size changes in bones or existence of birds from extinct population(s) or breeding region(s) with mensurally different bones from recent birds. This is the first study that suggests temporal size changes in bones may distort the species identification of archaeological remains according to modern size variations. Further studies are required to judge if this pattern is unusual or not.     

A study of dimensional differences of tooth marks (pits and scores) on bones modified by small and large carnivores

The use of tooth mark sizes to infer carnivore types when analyzing the modification of faunal assemblages has been criticized on the base of intense overlap in tooth mark size among differently sized carnivores. The present study analyzes this overlap and presents some critical explanations for it. This work is based on the largest collection of tooth pit dimensional data collected to date for some of the most relevant carnivore types. The study empirically shows that small and large carnivores can be clearly differentiated when using tooth pit size, with a higher discrimination when using tooth marks on dense shafts than on cancellous ends. It is argued that most previous studies of tooth mark sizes have reproduced a higher overlap probably because sample sizes were small, and experiments were carried out using small carcasses (which require a smaller bite force) or for a combination of factors.     

The effects of sample size on some derived measures in vertebrate faunal analysis

Analysis of three kinds of measures derived from archaeological and palaeontological faunal collections (measures of relative taxonomic abundance, measures of taxonomic diversity, and a measure proposed to distinguish natural from cultural bone) demonstrates that in many instances such measures may be, or are, a function of sample size. A procedure for detecting this situation is suggested, and the source of the interrelationships discussed.