Plasticity and Population Structure: Exploring Secular Trends in the Three- Dimensional Cranial Morphology of the Modern Portuguese

• Main Author: Weisensee, Katherine Elizabeth
• Published: Trace: Tennessee Research and Creative Exchange 2008
• Subjects: Anthropology
• Online Access: http://trace.tennessee.edu/utk_graddiss/352

Significant secular changes have been documented in several worldwide populations over the past 200 years; these changes include increased stature and weight, increased cranial vault height, and a narrowing of the cranial vault width (Angel 1976; Boas 1912; Jantz 2001; Jonke et al. 2007; Little et al. 2006). A variety of hypotheses have been proposed as to the origins of the observed changes. This dissertation uses a documented collection of skeletons from the 19th and 20th centuries to describe the precise nature of the changes using three-dimensional methods and explores possible causes underlying the changes including individual environmental effects, demographic parameters, and spatial effects. Three-dimensional cranial landmarks from 500 identified individuals from the New Lisbon Skeletal collection in Lisbon, Portugal were collected along with available demographic data. The birth years represented in the sample range from 1805-1960. The Portuguese sample provides the opportunity for understanding the genetic and environmental components of the observed changes. The highly circumscribed nature of the skeletal collection, which contains only individuals from the relatively homogenous Portuguese population, enables a comparison of the observed changes with information about individual environmental effects, such as socioeconomic status and health status. The impact of the demographic transition that characterizes modern populations is also examined; the modern demographic transition is characterized by a decrease in mortality followed by a decrease in fertility. Also, information regarding the place of birth and place of death for individuals in the sample is used to model the spatial effects on cranial morphology and to demonstrate the maintenance of genetic structure in spite of significant secular changes. In addition to providing a unique sample for testing theories related to the causes of secular trends, this research also provides a new way of documenting secular trends. In previous research, secular changes have primarily used traditional linear craniometric data, anthropometric data, or conscript records to document change. The use of three-dimensional data enables a more exact description of changes in the cranial form and provides the opportunity for a more precise understanding of the basis for change.