Biological mortality bias is the concept that within a population, the individuals who die (non-survivors) are biologically different from their surviving peers. Because non-survivors may have experienced more health insults during their lives than survivors, they may differ from survivors in their biological phenotypes. Thus, if biological mortality bias exists and is substantial in magnitude, interpretations of past population health made from skeletal samples (non-survivors) may not accurately reflect the health of the surviving population. This dissertation explores biological mortality bias as reflected in the growth of juvenile individuals aged birth to 12 years. Growth is known to be susceptible to environmental influences, and thus has been widely used by bioarchaeologists as a marker of general population health. However, the sensitivity of growth to environmental effects also makes it likely to be affected by biological mortality bias. The dissertation is composed of four separate scientific papers aimed at examining the effects of biological mortality bias from multiple perspectives. The first paper is a preliminary study contrasting: 1) body length between survivors and non-survivors in a sample of contemporary children; and 2) height and weight between survivors and non-survivors in a diseased sample of girls admitted to a historical tuberculosis sanatorium. The following three papers draw data from a sample of full body post-mortem computed tomography (CT) scans of contemporary children. More specifically, the second paper contrasts dental development between survivors and non-survivors using transition analysis. The third paper presents a protocol for anthropological measurement of long bones in CT scans and reports on its accuracy and replicability. The fourth paper makes use of this protocol for data collection to compare long bone length for age between survivors and non-survivors. Evidence for biological mortality bias is found in linear growth as measured both by full body anthropometrics and long bone lengths, but not in dental development as measured by dental formation stages. These findings reinforce confidence in dental age estimates, but suggest that mortality bias may complicate bioarchaeological analysis of juvenile skeletal remains.
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Thesis advisor: Cardoso, Hugo F.V.
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