Testing for Size and Allometric Differences in Fossil Hominin Body Mass Estimation
- by Natalie M. Uhl, Christopher W. Rainwater and Lyle W. Konigsberg
“Body size reconstructions of fossil hominins allow us to infer many things about their evolution and lifestyle, including diet, metabolic requirements, locomotion, and brain/body size relationships. The importance of these implications compels anthropologists to attempt body mass estimation from fragmentary fossil hominin specimens. Most calculations require a known “calibration” sample usually composed of modern humans or other extant apes. Caution must be taken in these analyses, as estimates are sensitive to overall size and allometric differences between the fossil hominin and the reference sample.
This research places body mass estimation into the framework of multivariate calibration. Estimators are extended to the calculation of prediction intervals for “new” cases as well as estimation of mean body mass and confidence intervals when a taxon provides more than one case for estimation. Models are evaluated through “leave one out” validation, simulations of extreme samples, and finally, application to two specific fossil hominin specimens, KNM-WT 15000 (Homo erectus) and LB1 (Homo floresiensis). The R and Rx statistics (Brown and Sundberg 1987), both of which are quadratic forms, result from calibration analyses and in this context quantify allometric and size departure of each of these hominins from the human reference material. Our results show that body mass estimation is possible for fossil hominins using a human reference sample because prediction intervals expand around individual estimates of body mass when the R statistic increases. The choice between Bayesian and maximum likelihood approaches can largely be based on the Rx statistic, as significant values for this statistic oblige us to argue against the Bayesian approach” (read more/not open access).
(Source: American Journal of Physical Anthropology, in press 2013; top image: johnhawks.net)
