New method for assessing changes in growth and sexual dimorphism in paleoepidemiology

This paper has three goals. First, traditional methods used for analyzing growth disruption (GD) and sexual dimorphism (SD) in prehistoric skeletal populations are critiqued. Second, a new method, using adult vertebrae, is presented which helps overcome these limitations. Third, this new method is then tested in the Dickson Mounds skeletal population. Between A.D. 950 and 1300 this population underwent a transition from hunting and gathering (PreMississippian: PreMiss.) to maize horticulture (Mississippian: Miss.). Previous research has found a decrease in long bone length in Miss. children, but no difference in adults, or a change in SD. Could this be due to catch-up growth? In the adult skeleton vertebral neural canals (VNCs) size and vertebral body heights (VBHs) can easily be measured. VNCs generally cease growth by early childhood, whereas VBHs grow through young adulthood. This new method offers inference into prehistoric GD and SD previously thought impossible. For example, if VNCs are reduced, but not VBHs, it implies early GD with subsequent catch-up growth. If both VNCs and VBHs are reduced, GD was presumably chronic. Moreover, within this framework, preadult SD can be examined. Results from Dickson show that early GD was followed by catch-up growth. There was a significant change in SD, with females becoming smaller. They had chronic GD. Miss. males had early GD, followed by catch-up growth. Indeed, Miss. males, compared to PreMiss. males, had significantly larger VBHs. Together, these results suggest females lost, but males gained, social status. Thus, vertebral morphometrics may be an invaluable new tool for paleoepidemiologists.