The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)


Geometric methods of body mass estimation in small-bodied hominins

STEVEN E. CHURCHILL1, SHILPA SRIDHAR1, NOËL CAMERON2 and CHRISTOPHER S. WALKER1.

1Department of Evolutionary Anthropology, Duke University, 2Centre for Global Health and Human Development, Loughborough University

March 26, 2015 , Gateway Ballroom 2 Add to calendar

Body mass is an ecologically- and biomechanically-important variable in the study of early hominin biology. Regressions derived from recent human samples allow for the reasonable estimation of body mass of later hominins (genus Homo) from hip joint dimensions, but potential differences in hip abductor biomechanics across hominin taxa render questionable their use with early hominins (such as Australopithecus). Geometric methods of mass estimation using stature and bi-iliac breadth avoid this problem, but their applicability to early hominins that differed in body size and proportions from adult recent humans has not been demonstrated.

Here we use mean stature, bi-iliac breadth, and body mass from global samples of human children ranging in age from 6-12 years (N = 530 age- and sex-specific samples, from the literature) to evaluate the accuracy of these methods when applied to small-bodied samples (who also differ in proportions from adult human reference samples). Geometric methods systematically underestimated mass in the younger (6-9 year old) age groups (median prediction errors ranging from -0.2 to -5 kg, representing median errors of 1.0-32.7%), who are smaller on average (grand mean body masses of 19.7-26.3 kg) than most australopiths (ca. 29-45 kg). These methods moderately overestimated mass in the older (10-12 year old) groups (by 1.2 to 3.2 kg [3.9-7.9%]), whose body masses (grand means of 29.2-36.2 kg) fall in the range of adult Australopithecus. While further testing with additional samples is warranted, these results suggest that stature and bi-iliac breadth may reasonably be used to estimate mass in small-bodied hominins.