2026-05-11 マックス・プランク研究所
Colormap of trabecular bone density in the hip, knee and ankle reflecting joint flexion in Paranthropus robustus linked to frequent climbing.© Christopher M. Smith
＜関連情報＞
- https://www.mpg.de/26471037/swartkrans-paranthropus-and-sterkfontein-australopithecus-had-different-locomotor-repertoires
- https://www.pnas.org/doi/10.1073/pnas.2532193123
南アフリカのスワートクランス産パラントロプスとステルクフォンテイン産アウストラロピテクスは、異なる運動能力を持っていた Swartkrans Paranthropus and Sterkfontein Australopithecus from southern Africa had different locomotor repertoires
Marine Cazenave, Annalisa Pietrobelli, Andrea Luková, +16 , and Matthew M. Skinner
Proceedings of the National Academy of Sciences Published:May 11, 2026
Significance
Southern African Paranthropus robustus and Sterkfontein Australopithecus are traditionally distinguished by their dentition and cranial architecture, while postcranial anatomy has often been assumed to be similar, reflecting a combination of terrestrial bipedalism and some arboreal climbing. To test this assumption, we examined internal structure of a recently discovered P. robustus articulating femur and tibia, focusing on cortical and trabecular bone of the ankle, knee, and hip. We show clear functional differences: P. robustus exhibits features indicative of joint postures likely associated with frequent climbing, whereas Sterkfontein Australopithecus shows a pattern consistent with comparatively more frequent terrestrial bipedalism. Thus, the younger P. robustus likely retained more arboreal behaviors than the older Sterkfontein Australopithecus, consistent with distinct locomotor repertoires and ecological niches.
Abstract
Southern African hominin fossils traditionally attributed to Paranthropus robustus and Australopithecus africanus are differentiated from each other by their dentition and cranial architecture, but their postcranial anatomy has typically been regarded functionally as broadly similar (i.e., terrestrial bipedalism with some degree of arboreal locomotion). Testing the hypothesis of a similar locomotor repertoire between these two taxa has been complicated by a lack of postcranial fossils attributable to P. robustus. Here, we detail our comparative examination of the internal bone anatomy of a recently described c. 1.8 Ma P. robustus articulating femur and tibia, which suggests distinct patterns of joint loading and locomotor behavior. Our analysis of cortical bone in the hip and trabecular bone in the ankle, knee, and hip joints suggests that P. robustus habitually adopted a high frequency of ankle, knee, and hip flexion, as required for climbing, while Australopithecus from a c. 3.4 Ma level at the site of Sterkfontein displays a more modern human-like structural pattern across the lower limb joints consistent with comparatively more frequent terrestrial bipedalism. These results reveal that geologically younger P. robustus likely used arboreality more frequently than older Sterkfontein Australopithecus. Together with differences in masticatory behavior, this line of evidence indicates that these two hominin taxa occupied distinct ecological niches.
