The Ontogeny of Postcranial Robusticity and Shape in Middle Holocene Cis-Baikal Hunter-Gatherer Populations

  • Author / Creator
    Osipov, Benjamin
  • This dissertation investigates changes in bone robusticity and shape from birth to young adulthood in Middle Holocene (~7,500- 3,700 years cal BP) Cis-Baikal hunter-gatherer populations. First, how biomechanical properties change with age throughout the upper and lower limb is evaluated. Second, the study uses bone robusticity and shape to examine chronological and inter-cemetery variation in the genetics, health, and behavior of Cis-Baikal juveniles. Robusticity and shape are quantified throughout the appendicular skeleton using cross-sectional geometry. Inter-limb robusticity ratios, and asymmetry in upper limb robusticity and shape are also analyzed. Ontogenetic patterning is evaluated using visual analysis, curve-fitting, and statistical comparisons. Statistical tests and visual analysis are used to detect differences between individuals from different archaeological periods and cemeteries, as well as the age at which these differences emerged. Analysis of general developmental patterns highlights the interacting influences of body mass, activity levels, and hormones on age-related change in external and internal bone dimensions as well as robusticity. Lower limb shape and interlimb robusticity ratios track adaptation of the lower limb to changes in body shape, bipedal locomotion, and weight bearing. Upper limb shape development is consistent with adaptation to multi-axial bending and torsion, but there are regional differences. These likely reflect heterogeneity in range of motion and the localized influence of specific muscles and ligaments. Analysis of asymmetry development shows that right dominance emerges earlier in the humerus than the clavicle or ulna, indicating that this element is most sensitive to side differences in mechanical loading. Comparisons of individuals from different archaeological periods and cemeteries find little evidence for differentiation attributable to genetic variation prior to the age of 16 years. Differences in size-unstandardized robusticity, body mass estimates, and interlimb robusticity ratios indicate Late Neolithic individuals had higher body masses than Early Neolithic juveniles from shortly after birth, suggesting the former group experienced less developmental stress. The study also indicates geographic variation in developmental stress during the Early Neolithic. Juveniles buried at Lokomotiv appear to have had lower body masses for age than contemporaneous Shamanka juveniles. Although body mass differences complicate behavioral comparisons, Early Neolithic juveniles appear to have been more mobile and placed higher loads on their upper limb than Late Neolithic juveniles after the age of six years. Higher Early Neolithic juvenile mobility may reflect the depletion of terrestrial resources by more densely concentrated populations. Alternatively, mobility may have declined in the Late Neolithic due to a greater abundance or more homogeneous distribution of terrestrial game. The development of stronger upper limbs in the Early Neolithic is consistent with juveniles being more involved in fishing or other forms of specialized labor. The former appears especially likely given strong evidence for greater dependence on aquatic resources during this period. The greater differentiation of Early Neolithic Shamanka than Lokomotiv from Late Neolithic Ust-Ida reflects either small Lokomotiv sample size or the unique foraging strategies of Shamanka groups. Sexual dimorphism in bone robusticity and limb shape appears to have been established in all archaeological periods by the end of adolescence. Strength differences may partly result from the effect of sex hormones on bone accrual. However, differences in workloads and mobility levels are also consistent with the sexual division of labor. Lastly, chronological change in behavior appears more pronounced among females than males. This is consistent with the results of prior studies, which hypothesize that female subsistence behavior changed more throughout the Middle Holocene. Overall, analysis of Cis-Baikal juveniles demonstrates that bone robusticity and shape undergo significant changes during development that reflect variation in mechanical environment throughout the body. Changes in robusticity and shape between archaeological period are consistent with variation in juvenile health, mobility levels, and economic roles.

  • Subjects / Keywords
  • Graduation date
    Spring 2018
  • Type of Item
  • Degree
    Doctor of Philosophy
  • DOI
  • License
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