The Sheep Project (1): determining skeletal growth,timing of epiphyseal fusion and morphometric variation in unimproved Shetland sheep of known age,sex, castration status and nutrition

The Sheep Project was designed to investigate the effects of castration, breeding age and nutritional plane on bone growth, epiphyseal fusion, tooth eruption and tooth wear in sheep. The project investigates a population of 356 unimproved Shetland sheep skeletons evenly distributed between females bred at different ages, males and castrates, raised on either high or low nutritional planes. This first instalment focuses on two aspects of our larger study, namely bone growth and epiphyseal fusion as affected by sex, castration and nutrition. Nutrition, sex and castration are shown to influence bone growth in ways that are often element-dependant and not consistent through time. We demonstrate that metric variability (variance) is strongest in males, with little difference between females and castrates, and that, in our sample, nutrition has little influence on variance in any sex cohort. Of importance to the development of models of past animal management this study demonstrates that the standard epiphyseal fusion ranges used by zooarchaeologists are too narrow in most instances and do not account for the large variation between sexes or the lesser variation between planes of nutrition. We recommend methods for recognizing castration and the presence of more than one sheep breed, or type, within the zooarchaeological record.     

Genetic sexing to determine the optimal discriminant functions for the analysis of archaeological remains from El Hierro (Canary Islands)

A correct sex assignment of a given bone or bone fragment is of paramount importance for the archaeologist, anthropologist and in forensic medicine. Discriminant functions, combining several anthropometric measurements obtained from individuals with known sex are useful tools for this purpose, but it is essential to know exactly the sex from which the measures are obtained. This is an easy task in modern populations, but it is problematic in ancient ones, since even when the entire skeleton is available, diagnosis of sex is not 100% accurate. Sexing by genetic methods by amplifying the first intron of the amelogenin gene constitutes a much more accurate method for sexing bones and may be the gold standard for further elaboration of discriminant functions which may serve for sexing new bones dug up in future excavations. With this aim we have genetically sexed 52 (out of 59) tibiae belonging to the prehispanic population of El Hierro, in the Canary Islands, identifying 18 women and 34 men, and then, performed discriminant functions combining several anthropometric variables. These functions show a high accuracy in sex diagnosis (94.2%; area under ROC curve = 0.954 with the best of the functions), so that they allow correct sexing of tibiae or tibiae fragments (only proximal third, distal third or midshaft). Thus, genetic sexing obviates the problem of finding an accurate gold standard for the elaboration of discriminant functions for ancient bones. This method could be applied to other populations of different antiquity and different ethnicity.     

Canary islands aborigin sex determination based on mandible parameters contrasted by amelogenin analysis

Sex determination using mandible parameters is population dependent. In order to assess which measurements better characterize sex in prehispanic individuals from the Canary Islands, we blindly contrasted the results obtained by visual inspection and osteometric measurements with those obtained by molecular sexing using amelogenin ancient DNA analysis on teeth from the same material. Unambiguous sex classification was achieved by amplification of sex specific amelogenin alleles in 56 out of 76 mandibles (73.78% of the cases). Visual inspection led to a correct diagnosis in 66.04% of cases, with a greater proportion of errors for female (54.17%) than male (17.24%) mandibles. Osteometric measurements were able to assign sex correctly in 72.2% in the best of cases (mandibular height), a proportion similar to that obtained using a discriminant function (71.2%). By logistic regression analysis, ramus breadth, index ramus breadth/ramus height and mandibular length were the parameters independently related with a mistaken diagnosis of female sex, whereas bigonial width, ramus height and mandibular length were the parameters more closely and independently related to a mistaken diagnosis of male sex. In conclusion, diagnosis based on visual examination of the mandible or on its metric measurement only serves to roughly estimate sex with an accuracy of around 70% or less, at least among the prehispanic population from Gran Canaria. Amplification of amelogenin alleles leads to unambiguous identification of male and female alleles in 73.68% of cases, at least among the prehispanic population from Gran Canaria.     

Molecular and osteometric sexing of cattle metacarpals: a case study from 15th century AD Beja,Portugal

In the course of a zooarchaeological survey of Holocene sites in southern Portugal, a substantial size increase of cattle bones was noted following the Christian reconquista of the 11th–13th centuries AD. A size increase in the course of time within a lineage of domestic livestock is usually considered to represent animal improvement. However several other factors including sex may influence the average size of a sample of mammal bones – cattle exhibit considerable sexual size dimorphism, with bulls being larger than cows. A histogram of the distal widths of a large (n = 44) sample of cattle metacarpals from 15th century Beja (Alentejo, Portugal), revealed a bimodal distribution. It was assumed that the large measurements belonged to males and the small to females. In order to rule out the possibility of a post-Moslem change in the sex ratio of cattle, a sub-sample of 21 cattle metacarpals from Beja was selected and we used genetic markers to identify the sex of the animals to which these metacarpals belonged. The ancient DNA sex of all specimens agreed with the previously assumed sex as determined osteometrically. We conclude that the two nearly separated peaks for the metacarpal distal width measurements do indeed indicate sex. A similar bimodal distribution was obtained from another large but earlier sample of cattle metacarpals from Moslem Alcáçova de Santarém (9th–12th century AD). Although these have not been molecularly sexed and since osteometric sexing has now been validated, we conclude that both small (female) and large (male) peaks are smaller than the 15th century ones and that there was an overall size increase or improvement of cattle in this region. Why the Christians improved cattle is unclear, but a selection for larger beeves for meat is one possibility as is the selection of more robust cattle for power. The spread of the quadrangular or chariot plough in Iberia is known to have occurred at this time. We then use the genetically sexed metacarpals to determine which measurements provide reasonable distinction between the sexes. Both the distal width (BFd; as already noted by Svensson et al., 2008; in Swedish medieval cattle) and the width of the lateral condyle (WCL) offer the best distinction. We also used them as a reference ‘collection’ to sex the medieval and post-medieval cattle metacarpals from Launceston Castle in England. This re-visit of the Launceston data corroborates other evidence indicating increased specialisation (milk and veal) in post-medieval cattle husbandry in England.