Evidence for habitual climbing in a Pleistocene hominin in South Africa

Bibliographic Collection: 
Publication Type: Journal Article
Authors: Georgiou, Leoni; Dunmore, Christopher J.; Bardo, Ameline; Buck, Laura T.; Hublin, Jean-Jacques; Pahr, Dieter H.; Stratford, Dominic; Synek, Alexander; Kivell, Tracy L.; Skinner, Matthew M.
Year of Publication: 2020
Journal: Proceedings of the National Academy of Sciences
Pagination: 201914481
Date Published: 2020/03/26
Publication Language: eng

Here we present evidence of hominin locomotor behavior from the trabecular bone of the femur. We show evidence for habitual use of highly flexed hip postures, which could potentially indicate regular climbing in a South African hominin from Sterkfontein, which is either Paranthropus robustus or Homo. Second, we present evidence that Australopithecus africanus likely did not climb at the frequencies seen in extant nonhuman apes, and exhibits a modern, human-like pattern of loading at the hip joint. These results challenge the prevailing view of a single transition to bipedalism within the hominin clade by providing evidence of climbing in a more recent, non-Australopithecus South African hominin, and add to the increasing evidence for locomotor diversity in the hominin clade.Bipedalism is a defining trait of the hominin lineage, associated with a transition from a more arboreal to a more terrestrial environment. While there is debate about when modern human-like bipedalism first appeared in hominins, all known South African hominins show morphological adaptations to bipedalism, suggesting that this was their predominant mode of locomotion. Here we present evidence that hominins preserved in the Sterkfontein Caves practiced two different locomotor repertoires. The trabecular structure of a proximal femur (StW 522) attributed to Australopithecus africanus exhibits a modern human-like bipedal locomotor pattern, while that of a geologically younger specimen (StW 311) attributed to either Homo sp. or Paranthropus robustus exhibits a pattern more similar to nonhuman apes, potentially suggesting regular bouts of both climbing and terrestrial bipedalism. Our results demonstrate distinct morphological differences, linked to behavioral differences between Australopithecus and later hominins in South Africa and contribute to the increasing evidence of locomotor diversity within the hominin clade.

DOI: https://doi.org/10.1073/pnas.1914481117
Short Title: Proc Natl Acad Sci USA