Unpacking the trunk: pelvic-thoracic relationships in modern Homo sapiens
Date
2024
Journal Title
Journal ISSN
Volume Title
Abstract
It is generally accepted that throughout the history of the genus Homo, shifts in body morphology have aligned with the emergence of distinct hominin populations (Ruff, 1991, 1994, 2010; Schmid et al., 2013; Walker & Leakey, 1993). The human trunk, comprised of the ribcage, pelvis, and spine, contributes the most to overall body shape. However, how the thorax and pelvis are morphologically related in modern humans is not well understood. The fragmented nature of the human fossil record poses challenges in reconstructing the morphology of the trunk. Research on extant nonhuman ape morphology has suggested covariance between the inferior ribcage and upper pelvis, and it has been proposed that this pattern holds for premodern hominin groups (Schmid, 1983; Schmid et al., 2013). This expectation of covariance between the upper and lower portions of the trunk has allowed researchers to infer body shape and size with incomplete remains (Schmid, 1983; Schmid et al., 2013; Jellema et al., 1993). However, recent findings have served to challenge previously accepted trends in hominin body shape, calling into question whether the hominin trunk is integrated as was previously thought (Arsuaga et al., 1999; Day, 1971; Rosenberg, 2007; Simpson et al., 2008). The current study expands on previous work by Torres-Tamayo et al. (2018, 2020). Five linear measurements from a mixed sample of 85 living humans were taken from computed topography scans rendered in 3D. Results suggest a minimal correlation between pelvic dimensions and inferior ribcage width, with some variations observed by sex. Understanding this relationship in modern humans aids in evaluating researchers' expectations when interpreting past hominin body shapes and offers new insights into the origins of modern human and neandertal anatomy. Since evidence of integration is weak, results suggest that the thorax and pelvis may be under different selective pressures in modern H. sapiens.
Description
Rights Access
Subject
modern human variation
body shape
torso integration