A paleodemographic assessment of mortality and fertility rates during the second demographic transition in rural central Indiana

Abstract

OBJECTIVES: Since its inception, skeletally based paleodemographic research has emphasized the utility of biocultural models for interpreting the dynamic relationship between the sociocultural and ecological forces accompanying demographic transitions and shaping populations' health and well-being. While the demographic transition associated with the Neolithic Revolution has been a common focus in bioarcheology, the present study analyzes human skeletal remains from a large 19th century cemetery in central Indiana to examine population dynamics during the second demographic transition, a period generally characterized by decreasing fertility rates and improvements in life expectancy. This study demonstrates the potential to methodologically identify regional variations in the timing and interactions between broad-scale socioeconomic changes and technological advancements that characterized the time period through observed changes in survivorship and fertility based on age-at-death distributions. MATERIALS AND METHODS: This study uses three temporally distinct samples (AD 1827-1869; 1870-1889; 1890-1935) from the Bethel Cemetery (n = 503). Kaplan-Meier survival analyses with a log- rank tests are utilized to evaluate survivorship and mortality over time. Next, Cox proportional hazard analyses are employed to examine the interaction between sex and time as covariates. Finally, the D0-14/D ratio is applied to estimate fertility for each of the three temporally bounded cohorts. RESULTS: The Kaplan-Meier survival analyses and Cox proportional hazard modeling revealed statistically significant differences in survivorship between the three time periods. Age-specific mortality rates are reduced among adult female and male age classes in this rural community over the course of the 19th and early 20th centuries, resulting in the increasing life expectancies associated with the second demographic transition. While mortality in early adulthood was common during the first time period and decreases thereafter, sex was not identified as a meaningful covariate. The proportion of juveniles in the three temporal samples indicate that fertility rates were higher than national averages for the better part of the 19th century and subsequently declined around the turn of 20th century for this community. CONCLUSIONS: The results indicate temporal differences between the three periods, demonstrating increased survivorship and decreased mortality and fertility over time. These findings corroborate two key features of the second demographic transition characterized by the move from high rates of both fertility and mortality to reduced rates and a general easing of demographic pressures. The observed trends likely reflect improvements in health, coinciding the industrial advance and economic development within and around Indianapolis. While the socioeconomic factors characterizing the Industrial Revolution drove demographic shifts that parallel an equally important epidemiological transition, potential regional differences are discussed to highlight variability in the timing of demographic transitions. The paleodemographic methods utilized in this study demonstrate improved accuracy and efficacy, which ultimately advances researchers' potential to disentangle population-specific socioeconomic factors that may contribute to asymmetrical experiences of health and mortality.