Author(s): Jashashvili T.; Patel B.A.; Carlson K.J.; Heaton J.L.; Pickering T.R.; Clarke R.J.; Crompton R.; Kuman K.; Beaudet A.; Bruxelles L.; Stratford D.; Mcclymont J.
Source: American Journal of Physical Anthropology; Mar 2019; vol. 168 ; p. 113-114
Publication Date: Mar 2019
Publication Type(s): Conference Abstract
Available at American Journal of Physical Anthropology – from Wiley Online Library Full Collection
Abstract:The human wrist and hand, as a manipulation organ, has undergone morphological modification over human evolutionary history. As the hand was emancipated from use during locomotion, its structure and proportions changed, and phalangeal curvature reduced. Here, we summarize the initial description and comparison of hand and wrist bones of the StW573 skeleton discovered in the Sterkfontein Member 2 deposit (3.67 Ma) within the Silberberg Grotto, South Africa. Comparative study of StW573 and other Plio- Pleistocene hominins (e.g., Australopithecus afarensis, A. africanus, and A. sediba) demonstrates that geographical separation and adaptation to different habitats and terrain may have affected mosaic morphological adaptations in hand bones. For example, trapezium facet orientation, longitudinal angle, and the length/midshaft proportion of metacarpal 2 are morphologically modern human-like. In contrast, mediolateral base dimensions, head shape, and dorsal tapering of metacarpal heads are more like the features of A. afarensis. Overall, the wrist and hand bones of StW573 share morphometric features with A. afarensis, but they also express their own unique combination of characters. Even though climbing adaptations in the postcranial skeleton may persist in combination with those of bipedal locomotion in both species, the presence long- distance terrestrial bipedalism did not eliminate an arboreal locomotor component. Instead, within the degeneracy, perhaps triggered complexity in partitioning the function of the hand as a locomotor or manipulative organ. In this context, the almost complete set of hand and wrist bones from the same individual provides a unique opportunity to further unravel this complexity.