Comparative Morphometric Analysis of the Pelvis of LB 1 (Homo floresiensis)

Although there has been copious research on the postcranial functional morphology of Homo floresiensis, there has been relatively little study of its pelvis and its implications for interpretations of H. floresiensis locomotion. Here we present the first comparative morphometric analysis of the pelvis of LB 1, the holotype of H. floresiensis, using data derived from high-resolution micro-CT scans and situated within a broad, Plio-Pleistocene hominin context. This includes a novel quantitative measure of iliac flare in hominins to assess the australopith-like qualities of the LB 1 pelvis described by previous studies.

In a sample of extant humans and African apes and 26 fossil hominin pelves, we quantified linear and angular pelvic traits, with a focus on features that should provide functional insights into H. floresiensis locomotor behavior, including ilium orientation angle and lower ilium length. Morphometric and allometric hypotheses were investigated using Kruskal-Wallis tests, principal component analysis, and least squares regression.

Univariate analyses demonstrate that all pelvic features of LB 1 (except for ischium length) are within the ranges of variation exhibited by Homo sapiens. Multivariate analysis reveals that the H. floresiensis pelvis shares similarities with those of other Pleistocene Homo and some australopith individuals.

Overall, our results suggest that the pelvis of LB 1 is more Homo-like than previously described. While the mix of primitive and derived traits in the postcrania of H. floresiensis makes functional inferences challenging, our results from the pelvis suggest a human-like form of terrestrial bipedalism in this species.