Article
Human calcaneal variation relative to subsistence strategy, activity level, and footwear
Frontiers in Earth Science
(2023)
Abstract
Lower limb cortical and trabecular bone varies with human behavior, leading to
suggestions that activity level decreases have contributed to a more gracile
skeleton. Similar trends are likely present in calcaneal morphology due to its
locomotor role during heel strike. Such relationships exist in calcaneal trabecular
structure; however, they have yet to be investigated in external morphology. Here
entire external calcaneal shape is analyzed among three human populations that
vary in subsistence strategy, activity level, and footwear use (n = 93) to investigate
how calcaneal morphology varies relative to these factors. Calcanei were either
surface scanned or micro-CT scanned. Calcaneal external shape was analyzed
using a sliding semilandmark analysis with 1,007 semilandmarks. Semilandmarks
were allowed to slide along tangent vectors or planes to minimize the bending
energy of the thin plate spline interpolation function relative to an updated
Procrustes average. Final landmark configurations underwent a Generalized
Procrustes Analysis. Shape variation of Procrustes coordinates was summarized
using principal components analysis (PCA). Procrustes distances between the
average calcaneus of each population were calculated, and resampling statistics
run to test for significant differences. The three populations exhibit significantly
different calcaneal morphologies (p<0.001 for all pairwise comparisons) and
separate along the first three PCs (42.11% of variance). Hunter-gatherers have
superoinferiorly taller and mediolaterally wider posterior calcanei than sedentary
populations. This likely serves as an adaptation for increased load transfer through
the posterior calcaneus due to more active lifestyles. This is supported further by
variation among the two industrialized populations. The 19th–20th century
industrialized population exhibits a relatively mediolaterally wider posterior
calcaneus than the mid-20th century-born population, suggesting there has
been further gracilization of the calcaneus with increases in sedentary behavior
over the last century.
Keywords
- foot,
- ankle,
- geometric morphometrics,
- bipedalism,
- foraging
Disciplines
Publication Date
Summer 2023
Citation Information
Christine M Harper. "Human calcaneal variation relative to subsistence strategy, activity level, and footwear" Frontiers in Earth Science (2023) Available at: http://works.bepress.com/christine-harper/17/