Allometric scaling and growth: Evaluation and applications in subadult body mass estimation

Abstract

Objectives: Previously developed methods in subadult body mass estimation have not been tested in populations other than European-American or African-American.This study uses a contemporary Taiwanese sample to test these methods. Through evaluating their accuracy and bias, we addressed whether the allometric relationships between body mass and skeletal traits commonly used in subadult body mass estimation are conserved among different populations.Materials and Methods: Computed tomography scans of lower limbs from individuals aged 0-17 years old of both sexes were collected from National Taiwan University Hospital along with documented body weight. Polar second moment of area, distal femoral metaphyseal breadth, and maximum superior/inferior femoral head diameter were collected either directly from the scans or from reconstructed 3D models. Estimated body mass was compared with documented body mass to assess the performance of the equations.Results: Current methods provided good body mass estimates in Taiwanese individuals, with accuracy and bias similar to those reported in other validation studies. A tendency for increasing error with increasing age was observed for all methods.Reduced major axis regression showed the allometric relationships between different skeletal traits and body mass across different age categories can all be summarized using a common fitted line. A revised, maximum likelihood-based approach was proposed for all skeletal traits. Discussion:The results suggested that the allometric relationships between body mass and different skeletal traits are largely conserved among populations. The revised method provided improved applicability with strong underlying theoretical justifications, and potential for future improvements.

An alternative size variable for allometric investigations in subadults

“…The most common size variables across allometry research are body mass (Holliday & Franciscus, 2009;Ruff, 1991Ruff, , 2002Watkins & German, 1992;Yim et al, 2021) and a length measure, such as stature (Bogin & Baker, 2012;Buschang, 1982;Holliday, 1999;Meadows & Jantz, 1995).…”

“…The most common size variables across allometry research are body mass (Holliday & Franciscus, 2009; Ruff, 1991, 2002; Watkins & German, 1992; Yim et al, 2021) and a length measure, such as stature (Bogin & Baker, 2012; Buschang, 1982; Holliday, 1999; Meadows & Jantz, 1995). Unless working with a documented skeletal collection, which is not possible for paleoanthropologists and less common for bioarchaeologists, size variables are often calculated using linear regression methods (Elliott, Kurki, Weston, & Collard, 2016; Konigsberg et al, 1998; Lacoste Jeanson et al, 2017; Lundy, 1985), which may introduce sources of error because of incompatible reference samples or wide confidence intervals (Moore & Ross, 2012; Pelin & Duyar, 2003; Schaffer, 2016).…”

“…This study aims to address the persistent problems in selecting an appropriate size variable for ontogenetic allometry research. Methods for estimating subadult body mass and stature are not accurate and therefore do not lead to valid results if incorporated into allometry research (Cowgill, 2018; Langley, 2017; Robbins et al, 2010; Yim et al, 2021). As an alternative, many subadult allometry studies investigating bivariate relationships continue to use the brachial or crural index (e.g.…”