Focused life history data and linear enamel hypoplasia to help explain intergenerational variation in relative leg length within Taiwanese families

Abstract

This study first examines the hypothesis that significant intergeneration increases in stature within 85 Taiwanese families in two study locations were primarily the result of increases in subischial leg length. It then evaluates a second hypothesis that independent assessments of the extent of intergenerational change in childhood environments within these families helped account for parent-offspring differences in relative leg length. Childhood environments were assessed using two criteria: developmental environment scores derived from life history data and evidence of linear enamel hypoplasia (LEH). Relative leg length was represented in two ways, as either the difference between internally estimated sex-specific z-scores of sitting height and subischial leg length (z(D) = z(SH) - z(LL)) or as relative sitting height (RSH; sitting height/height x 100). Paired Student t tests indicated intergenerational increases in relative leg length were significantly greater than zero in both study locations (P < or = 0.012). The second hypothesis, tested using a hierarchical model with maximum likelihood estimation that allowed for nesting of more than one offspring per family, received support as midparent-offspring differences in composite scores were significantly positively associated with midparent-offspring differences in relative leg length. This was true alone (P = 0.018), and when significant associations with LEH prevalence among mothers and offspring were statistically controlled for (P = 0.010). Evidence also indicated that while the large majority of offspring were taller than their midparental average height (84.3%; 91/108), offspring who were taller were also more likely to have relatively longer legs than by chance alone (Fishers exact, P = 0.027).

Malnutrition‐related early childhood exposures and enamel defects in the permanent dentition: A longitudinal study from the Bolivian Amazon

“…Developmental enamel defects may also be caused by genetic and local intra-alveolar factors, such as primary tooth infection and trauma/injury to the primary dentition (Mellanby 1927; Sarnat and Schour 1941; Pindborg 1982; Goodman and Rose 1990; Seow 1991; Laskaris 2003; Golkari 2009; Skinner et al 2014). Developmental defects in the permanent dentition are thus generally interpreted as a non-specific indicator of metabolic disruption and physiological stress during early childhood (Rose et al 1978; White 1978; Goodman and Rose 1991; Floyd 2007). …”

Nutritional, developmental, and genetic influences on relative sitting height at high altitude

“…Schooling et al (2008b) suggest that in some cases environmental influences on parental generations may constrain their children's growth when environmental circumstances change. Floyd (2007) presented evidence that differences in relative leg length may be more apparent when environmental differences between the comparison groups are greater. In contrast, Schooling et al (2008a) argue that large environmental changes may accelerate skeletal maturation more than leg growth, leading to relatively shorter legs.…”

“…Clarifying the extent to which these body proportions are influenced by the same set of factors that have been found to affect other aspects of Andean growth is relevant to understanding the distinctive high-altitude Andean morphology and how high altitude affects growth. In addition, a better understanding of influences on leg and trunk growth in general is significant given the attention that these body proportions have received as indicators of childhood environmental quality and as potential markers of health risk (Bogin et al, 2002;Floyd, 2007;Frisancho et al, 2001;Gunnell et al, 1998a;Li et al, 2007;Schooling et al, 2008a,b. Nutritional status is expected to affect body proportions based on findings from a number of studies suggesting that advantageous environmental circumstances affect leg growth more than trunk growth. Many investigations of secular trends report that secular increases in stature are due more to increases in leg length than in trunk length, leading to relatively longer legs as body size increases (see, for example Bogin et al, 2002;Floyd, 2007;Jantz and Jantz, 1999;Tanner et al, 1982), and these findings are corroborated by studies showing that higher socioeconomic status is associated with relatively longer legs (Frisancho et al, 2001;Gunnell et al, 1998b;Li et al, 2007).…”

Intergenerational gains in relative knee height as compared to gains in relative leg length within Taiwanese families

“…This study builds upon a recent report that documents both significant increases in relative subischial leg length within Taiwanese families and a significant link between these changes and the extent of change in early childhood circumstances of parents and offspring (Floyd, 2007). Here, I compare the extent of change in relative knee height (RKH; knee height/height) to that of relative leg length (RLL; height minus sitting height/height) within these families.…”

“…Accumulating evidence indicates that variation in RLL is a particularly sensitive indicator of early childhood circumstances (Floyd, 2007;Frisancho, 2007;Li et al, 2007 and references within). But relatively less is known about how lower leg growth contributes to the range of responses as developmental environments change.…”