Distinguishing between archaeological sheep and goat bones using a single collagen peptide

We describe a method of isolating and analyzing a single collagen peptide able to distinguish between sheep and goat bone collagen. The 33 amino acid peptide from both sheep and goat collagen was sequenced and shown to differ between the two species at two positions. Analysis of a range of caprines indicated that the sequence changes occurred between the divergence of the Himalayan tahr (Hemitragus jemlahicus) and the ibex (Capra ibex) and that the proposed goat marker is diagnostic of all Capra species and breeds. The survival of these markers in archaeological bones was tested using a set of 26 ovicaprid specimens from Domuztepe, a Neolithic site in south central Turkey. These markers were used to test the osteological determination of 24 of the Domuztepe bones, and determine the species for two immature specimens. The collagen-peptide method has advantages over other non-morphological methods of sheep/goat distinction because of the long-term survival of collagen over other biomolecules such as ancient DNA. The results also highlighted the problems in relying upon one morphological criterion, in this case on the distal radius, to distinguish between sheep and goat bones.     

Pastures lost? A dental microwear study of ovicaprine diet and management in Norse Greenland

The management of ovicaprines by the Medieval Norse farmers in Greenland is explored using dental microwear analysis. Adult and juvenile ovicaprines from Norse contexts in Greenland are shown to exhibit microwear patterns very different to those in modern Greenlandic sheep; while modern sheep demonstrate microwear consistent with low levels of soil ingestion under extensive, low stocking-rate grazing regimes, Norse sheep/goat display striated microwear patterns indicative of high levels of soil ingestion and, potentially, overgrazing. This high abrasive grazing signature is present in the inland region of the Western Settlement from 1150 AD onwards, may be evident in the inland Eastern Settlement from an equally early date and is also detected during the later phases of occupation in the Western settlement (14th and 15th centuries AD). It is argued that these results provide further evidence that maladaptive grazing practices led to a decline in the viability of pastoral farming in Greenland, and, moreover, that overgrazing did not merely occur towards the end of the settlement as a consequence of the worsening climate of the ‘Little Ice Age’ but rather was present in both the Western and the Eastern Settlement from a relatively early date.     

An assessment of morphological criteria for discriminating sheep and goat mandibles on a large prehistoric archaeological assemblage (Kerma,Sudan)

This paper presents an assessment of all known dental and mandibular morphological criteria for differentiating sheep (Ovis aries) and goats (Capra hircus) using for the first time an archaeological sample of complete caprine skeletons (90 sheep and 13 goats) from burials at Kerma (Sudan, 3rd and 2nd millennia BC). The species determinations were assessed using cranial and post-cranial morphological criteria. Consequently, the reliability (percentage of correct determination) and efficiency (complementary percentage of intermediate scores i.e. neither sheep nor goat) of 38 individual dental criteria could be fully assessed using a prehistoric homogeneous domesticate population. We demonstrate that, for this sample, individual criteria for lacteal teeth are more reliable for sheep (sheep: 95 ± 3%) than the adult premolars (85 ± 5%) and molars (sheep: 88 ± 2%), whereas for goats premolar criteria were more reliable (83 ± 12%). For efficiency, lacteal dental criteria are better (goat: 97 ± 5%; sheep: 95 ± 3%) than those for premolar (goat: 85 ± 10%; sheep: 79 ± 5%) and molar (goat: 82 ± 6%; sheep: 83 ± 2). We also demonstrated that most isolated teeth can be determined with less than 10% error. However, on average, within specific age classes (0–1 year, 1–4 years and more than 4 years), isolated teeth increased in reliability and decreased in efficiency. The average reliability of the criteria for complete mandibles for each age class for goats and sheep was 100%, when the efficiency was 67, 40 and 50% for goats and over 90% for sheep. This is due to the effect of age on the efficiency of isolated criteria and the poor performance of specific criteria mainly those P3, M1 and M2. We conclude that separate species kill-off profiles are possible. The effect of age on dental criteria would not significantly change the interpretation for specific subsistence strategies focused on one particularly species.     

Assessing the reliability of criteria used to identify postcranial bones in sheep, Ovis, and goats, Capra

Criteria developed to distinguish between selected postcranial elements of sheep and goats are evaluated using modern specimens from the collections of the Field Museum of Natural History, the National Museum of Natural History, and the Museum of Anthropology and the Museum of Zoology, University of Michigan. Elements considered are: the distal humerus, proximal and distal radius, distal tibia, distal metapodials, astragalus, calcaneus, and the first and second phalanx. This evaluation includes an assessment of 1385 elements from 49 goat and 84 modern sheep skeletons. It also includes a blind test on elements drawn from 20 specimens taken by six analysts with differing levels of experience. Overall, the criteria evaluated are highly reliable, especially in goats and only slightly less so in sheep. A major exception is the distal tibia, where diagnostic criteria tested proved substantially less reliable than other criteria evaluated here. Strongly positive results were also obtained when the sample was partitioned by sex, domestic status, and age. Results of the blind test show some variability depending on the level of experience of the analyst, underscoring the need for training and access to adequate modern reference collections before attempting to apply these criteria to archaeological assemblages. The results of this assessment stand in stark contrast to those obtained in an earlier assessment of the reliability of criteria used to distinguish between mandibles and mandibular teeth of sheep and goats. In all but a few teeth, dental criteria proved to be much less reliable, especially in goats. They were also significantly less reliable in the identification of both younger and older animals. Unlike dental criteria, there are no biases introduced by variable reliability of postcranial criteria that distort taxon-specific harvest profiles based on long-bones.     

Culling profiles: the indeterminacy of archaeozoological data to survivorship curve modelling of sheep and goat herd maintenance strategies

The comparison of survivorship curves derived from seven different models aiming to reconstruct ancient sheep and goat herd maintenance strategies (e.g. optimization of wool, meat, and milk production) shows that many of these models cannot be distinguished statistically. This observation renders the current theoretical framework for reconstructing ancient herd maintenance strategies problematic, due to the possible indeterminacy of model data analysis. In order to assign empirically observed age-at-death data to a model of herd maintenance strategy, it is suggested that a direct fit of observed data to survivorship curves be forgone in favor of a binning procedure highlighting the differences between fewer and more distinguishable models. The incorporation of high-resolution sexing and taxonomic determination to coarse-grained age-at-death models may go a long way towards solving the current problem of indeterminacy.