Supernumerary heads to biceps brachii muscle and Asian population history

Supernumerary heads of biceps brachii are one of the most common anatomic variants in the muscular system and appear to develop under genetic control and vary in prevalence among populations. Variation in prevalence and morphology therefore has the potential to contribute to understanding of human population history. Until now, there has been no publication of the prevalence of the variant in Southeast Asian populations. The aim of this research is to document the prevalence and morphology of the variant in a sample of Thai cadavers and to consider the significance of the findings. The method used was dissection of arms of 162 donated cadavers at Khon Kaen University, Thailand. The sample showed high prevalence of third heads of biceps brachii in 35% of cadavers, compared with the prevalence of up to 25% reported in large samples worldwide. The sample also showed equal prevalence in males and females and one-third present bilaterally. This pattern is similar to that found in East Asia, and very different from the low prevalence found in South Asia. The morphology of the supernumerary heads does not appear to be different from elsewhere in the world based on the minimal comparable data available in the literature. The Southeast-East Asian pattern of prevalence is consistent with current theories of population history in the region and suggests anatomical variation of the postcranial soft tissues may ultimately contribute to understanding of past human migrations.

Using isotopic evidence to assess the impact of migration and the two-layer hypothesis in prehistoric Northeast Thailand

OBJECTIVES

The nature of the agricultural transition in Southeast Asia has been a topic of some debate for archaeologists over the past decades. A prominent model, known as the two-layer hypothesis, states that indigenous hunter-gatherers were subsumed by the expansion of exotic Neolithic farmers into the area around 2000 BC. These farmers had ultimate origins in East Asia and brought rice and millet agriculture. Ban Non Wat is one of the few archaeological sites in Southeast Asia where this model can potentially be tested. The site is located in the Mun River valley of Northeast Thailand, and divided into 12 phases that span over 2,000 years, from about 1750 BC to the end of the Iron Age (ca. 500 AD). These phases exhibit successive cultural changes, and current interpretation of the site is of an early hunter-gatherer population, with agriculturalists immigrating into the later phases.

METHODS

We analyzed strontium, oxygen, and carbon isotopes in tooth enamel from over 150 individuals, dating from the Neolithic to Iron Age, to assess extrinsic origins and differences in diet between early and later phases.

RESULTS

We find evidence of dietary and cultural differences between groups at Ban Non Wat during its early occupation, but little evidence for immigration from distinct environments beyond the Khorat Plateau of Northeast Thailand.

CONCLUSIONS

The lack of consistent isotopic differences between early and later Neolithic occupants at Ban Non Wat means that the site does not conclusively support the two-layer hypothesis.

Assessing Raman spectroscopy as a prescreening tool for the selection of archaeological bone for stable isotopic analysis

Stable isotope analyses for paleodiet investigations require good preservation of bone protein, the collagen, to obtain reliable stable isotope values. Burial environments cause diagenetic alterations to collagen, especially in the leaching of the organic bone content. The survival of bone protein may be assessed by the weight % collagen, % carbon and % nitrogen yields, but these values are achieved only after destructive chemical processing. A non-destructive method of determining whether bone is suitably preserved would be desirable, as it would be less costly than chemical processing, and would also preserve skeletal collections. Raman analysis is one such potential non-destructive screening method. In previous applications, Raman spectroscopy has been used to test both the alteration of the mineral portion of bone, as well as to indicate the relative amount of organic material within the bone structure. However, there has been no research to test the relationship between the Raman spectroscopic results and the survival of bone protein. We use a set of 41 bone samples from the prehistoric archaeological site of Ban Non Wat, Northeast Thailand, to assess if Raman spectroscopy analysis of the organic-phosphate ratio has a significant correlation with the weight % collagen, and carbon and nitrogen yields obtained by isotopic analysis. The correlation coefficients are highly statistically significant in all cases (r = 0.716 for collagen, r = 0.630 for carbon and r = 0.706 for nitrogen, p≤0.001 for all) with approximately or close to half of the variation in each explained by variation in the organic-phosphate ratio (51.2% for collagen, 39.6% for carbon, and 49.8% for nitrogen). Although the Raman screening method cannot directly quantify the extent of collagen survival, it could be of use in the selection of bone most likely to have viable protein required for reliable results from stable isotope analysis.

Is it health or the burial environment: differentiating between hypomineralised and post-mortem stained enamel in an archaeological context

Developmental enamel defects are often used as indicators of general health in past archaeological populations. However, it can be difficult to macroscopically distinguish subtle hypomineralised opacities from post-mortem staining, unrelated to developmental defects. To overcome this difficulty, we have used non-destructive x-ray microtomography to estimate the mineral density of enamel. Using a sample of deciduous teeth from a prehistoric burial site in Northeast Thailand, we demonstrate that it is possible to determine whether observed enamel discolourations were more likely to be true hypomineralised lesions or artefacts occurring as the result of taphonomic effects. The analyses of our sample showed no evidence of hypomineralised areas in teeth with macroscopic discolouration, which had previously been thought, on the basis of macroscopic observation, to be hypomineralisations indicative of growth disruption. Our results demonstrate that x-ray microtomography can be a powerful, non-destructive method for the investigation of the presence and severity of hypomineralisation, and that diagnosis of enamel hypomineralisation based on macroscopic observation of buried teeth should be made with caution. This method makes it possible to identify true dental defects that are indicative of growth disruptions.

Can dental caries be interpreted as evidence of farming? The Asian experience

The seminal development of control of food production and its social and biological effects on human populations has for a long time been one of the foci of prehistoric research. The relationship between diet and oral pathology is well recognised and accepted to the point where rates of dental caries in particular have been seen as indicative of subsistence mode. This is despite the complex aetiology of caries, with both genetic and environmental factors other than diet contributing to lesion frequency. Most publications considering prehistoric diet and caries acknowledge the contribution of non-dietary variables but provide a more comfortable dietary explanation, with the role of domesticated starchy staples paramount. This widespread acceptance of a simple relationship between dental pathology and starchy carbohydrates needs to be challenged, as there is no reason why one dietary component would be solely responsible for the development of caries or why all carbohydrates should have the same effect. Some years ago, on the basis of evidence from prehistoric rice farming communities in Southeast Asia, we questioned the relationship between dental caries and the presumptive increased carbohydrate consumption consequent to the adoption of agriculture. This paper reviews recent literature on the topic and presents evidence that there is still no simple or universally applicable explanation for patterns of changes in caries frequencies during human prehistory.

Leprosy and tuberculosis in Iron Age Southeast Asia?

The recent excavation of a sample of 120 human skeletons from an Iron Age site in the valley of the Mun River, a tributary of the Mekong River on the Khorat Plateau in northeast Thailand, has provided the largest sample from this period in the region to date. This paper reviews three individuals from the sample with pathological changes for which the differential diagnosis includes systemic infectious disease. In two of these, both males with lesions of the hands and feet, leprosy and psoriatic arthritis are discussed as differential diagnoses, with leprosy the most probable. In the third, a female with lesions of the spine, the differential diagnosis includes tuberculosis and nonspecific osteomyelitis. Tuberculosis is the most probable diagnosis. Although the focus of this paper is a presentation of the evidence for infectious disease at Noen U-Loke, the significance of probable diagnoses of mycobacterial diseases for the history of the diseases and for prehistory in mainland Southeast Asia is also briefly discussed.

Skeletal pathology in a prehistoric Pacific Island sample: Issues in lesion recording, quantification, and interpretation

This paper presents a profile of evidence of disease in a skeletal sample from Taumako Island, Southeast Solomon Islands, Melanesia, and aims to increase awareness of the prehistoric Pacific Island disease environment. It also addresses issues of lesion recording, quantification, and interpretation. Two methodologies for the determination of lesion prevalence were applied, one based on prevalence in observable individuals and one in skeletal elements. The aim of these methodologies was to provide objective data on skeletal lesions in this sample, with transparency in methods for application in comparative studies. The types of lesions observed were predominantly osteoblastic and affecting multiple bones, particularly in the lower limbs. The individual analysis yielded a prevalence of lesions affecting 56.4% of the postcranial sample from birth to old age. As expected, the skeletal element analysis yielded a lower prevalence, with 15.0% of skeletal elements affected. The skeletal element analysis also revealed a pattern of greater lower limb involvement, with a predilection for the tibia. The pattern of skeletal involvement was similar in both analyses, suggesting the validity of employing either method in paleopathological studies. A differential diagnosis of the lesions included osteomyelitis, treponemal disease, and leprosy. Metabolic disease was also considered for subadult lesions. Based on lesion type, skeletal distribution, and epidemiology of lesions in the sample, an etiology of yaws (Treponema pertenue) was suggested as responsible for nearly half the adult lesions, while multiple causes, including yaws, were suggested for the lesions in subadults.

Missing lateral incisors in Iron Age South-East Asians as possible indicators of dental agenesis

The absence of lateral incisors is generally a reflection of agenesis or hypodontia, with a significant genetic basis and possibly environmental influence on the phenotypic expression. A human skeletal sample from the Iron Age cemetery of Noen U-Loke in Thailand has a very high prevalence at 79% of adults (30/38) with at least one incisor missing in either maxilla or mandible. If the cause of this high rate is genetic, it may be indicative of homogeneity, and, therefore, endogamy and probably isolation, of the population represented. Supporting agenesis as the explanation for this is the lack of space between the central incisors and canines in more than half the cases. An alternative explanation is that the teeth may have been lost during life through pathology or deliberate removal (ablation). There is no evidence in the form of remodelled lesions for pathological loss of the teeth. Although there were no significant differences between males and females in the numbers of teeth missing, there were significant differences in the patterns of loss, with males having more missing teeth on the right and females more on the left. No evidence was found in the clinical literature of agenesis involving side preference by sex, so this may indicate deliberate removal of the teeth. Males were also more likely than females to have no space for the missing teeth. Ablation of teeth has been recorded in other prehistoric South-East Asian populations but in these cases the evidence was much clearer. Agenesis seems to offer the most likely explanation for the missing teeth at Noen U-Loke and if so, indicates that a small, isolated population may develop a very high rate of hypodontia, with a side preference dependent on sex.

Anemia, genetic diseases, and malaria in prehistoric mainland Southeast Asia

The analysis of a sample of skeletons from the 4,000-year-old site of Khok Phanom Di on the coast of central Thailand has identified a number of individuals with skeletal evidence suggestive of severe anemia. The differential diagnosis of the lesions is discussed and the presence of one of the thalassemia syndromes is proposed. The implications of this for southeast Asian prehistory are discussed. The presence of these conditions has been suggested in previous analyses of prehistoric southeast Asian populations, but this is the first population in which the evidence, including postcranial responses, is presented in detail.