Exploring Patterns of Appositional Growth Amongst Urban Children

Gains in relative cortical area during growth and their relationship to nutrition, body size, and physical activity

OBJECTIVES

In studies of growth in the past, low percentage of cortical area (%CA) is commonly attributed to poor general health, due to factors including poor nutrition, low socioeconomic status, or other physiological stressors. What constitutes low relative cortical dimensions has not been established across a diverse range of human skeletal samples. This study examines %CA in a large immature skeletal sample to establish typical variation in humans with consideration of both body mass and subsistence strategy.

MATERIALS AND METHODS

Percentage of cortical area was calculated at the midshaft of the humerus, femur, and tibia in seven skeletal samples. Age at death was estimated from dental development, and body mass from bone dimensions. Patterns of %CA with age and log-transformed body mass were examined in the pooled sample and compared among samples using LOESS regression, Welch's ANOVA, and Kruskal-Wallis tests.

RESULTS

Across all samples, %CA displays a generally non-linear pattern, but variation in %CA with age was high, particularly in samples with lower levels of %CA. There was no relationship between %CA and age-adjusted body mass.

DISCUSSION

The lack of a relationship between %CA and body mass suggests that %CA should not be used as an indicator of mechanical loading. The variation present across samples implies that appositional bone growth is affected by physiological stress in varying ways. Without a deeper understanding of what is "typical" for long bone development, it is impossible to draw conclusions about individual or population level health.

Toward a bioarchaeology of urbanization: Demography, health, and behavior in cities in the past

Urbanization is one of the most important settlement shifts in human history and has been the focus of research within bioarchaeology for decades. However, there have been limited attempts to synthesize the results of these studies in order to gain a broader perspective on whether or how urbanization affects the biology, demography, and behavior of humans, and how these potential effects are embodied in the human skeleton. This paper outlines how bioarchaeology is well-suited to examine urbanization in the past, and we provide an overview and examples of three main ways in which urbanization is studied in bioarchaeological research: comparison of (often contemporaneous) urban and rural sites, synchronic studies of the variation that exists within and between urban sites, and investigations of changes that occur within urban sites over time. Studies of urbanization, both within bioarchaeology and in other fields of study, face a number of limitations, including a lack of a consensus regarding what urban and urbanization mean, the assumed dichotomous nature of urban versus rural settlements, the supposition that urbanization is universally bad for people, and the assumption (at least in practice) of homogeneity within urban and rural populations. Bioarchaeologists can address these limitations by utilizing a wide array of data and methods, and the studies described here collectively demonstrate the complex, nuanced, and highly variable effects of urbanization.