The magnitude of changes in linear growth within Taiwanese families: intrinsic sex-associated biology, socially mediated behaviors, or both?

How much impact do gains in height have on shoulder breadths within Taiwanese families?

OBJECTIVES

This study investigates allometric changes in shoulder breadths relative to changes in stature arising from rapidly changing developmental circumstances within 107 Taiwanese families. It speaks to broader issues related to the extent of phenotypic plasticity of body breadths humans are capable of in response to reductions in developmental stressors.

METHODS

An examination of relationships between shoulder breadth and height within individuals in each generation was followed by evaluation of patterns of difference between same-sex parent-offspring pairs in height and shoulder breadth.

RESULTS

Height was similarly positively correlated with shoulder breadth within fathers, mothers, sons, and daughters (P ≤ 0.002). Variance accounted for ranged from an adjusted R² of 0.201 among fathers to 0.151 for sons, with mothers' and daughters' values being 0.187 and 0.181, respectively. Comparisons of differences within families indicate that parents who were shorter than their same-sex offspring also tended to have modestly narrower biacromial breadths (father-son pairs: adjusted R²  = 0.112; t = 2.82, P = .007; mother-daughter pairs: adjusted R²  = 0.135; t = 2.97, P = 0.005).

CONCLUSIONS

Taken as a whole, results here support the view that secular changes in stature are not accompanied by similar changes in body breadths, perhaps so that responses to developmental environmental improvements do not alter thermoregulatory equilibria that reflect long-term evolutionary processes. These results indirectly constrain plausible hypotheses about how ancestors of Austronesian speakers altered their body size and shape as they voyaged to Fiji, Western Polynesia, and beyond.

The influence of variation in parental height dimorphism on same-sex parent-offspring height differences

OBJECTIVE

This study evaluates how adjusting for parental height dimorphism influences height differences among parents and same-sex offspring distinguished by parents' early backgrounds.

PARTICIPANTS AND METHODS

Regression analyses using data from independent groups of Taiwanese families, 56 with sons and 51 with daughters, evaluate how adjusting for parental height dimorphism influences same-sex parent-offspring height differences among families grouped by grandfathers' occupations into three status categories reflecting good to relatively poor early parental environments.

RESULTS

Parental height dimorphism was statistically significantly associated with same-sex parent-offspring height differences (father-son: mean Δ = 3.88 cm, β = -71.47 ± 11.49 SE, t = -6.22, p ≤ .0005; mother-daughter: mean Δ = 4.15 cm, β = 80.46 ± 18.52 SE, t = 4.35, p ≤ .0005). Adjusted mean father-son differences increased significantly across grandfathers' occupation categories (Privileged, Δ = 0.60, Business, Δ = 4.06, Farming & Labor, Δ = 5.28; p = .011). Mother-daughter differences were substantial, from 3.33 cm to 5.06 cm, but did not differ significantly across occupational categories (p = .63).

DISCUSSION

Adjustments here for variation in parent height dimorphism did not alter original interpretations that while female growth may be more canalized, it is similarly capable of responding to improvements in developmental contexts. Patterns of same-sex parent-offspring height differences across grandfathers' occupational categories remain best accounted for by Taiwan's rapidly expanding economy, substantial income equity and reductions in biases favoring sons over daughters. Adjustment for sub-group variation in parental height dimorphism should be considered in similar studies in the future.