Inferences about fossil hominin locomotion through 3D morphometric analysis of wrist ligament insertion sites.

Understanding the evolution of wrist anatomy in fossil hominins is essential for reconstructing their locomotor behavior and manipulative capabilities. Traditionally, most studies have focused on bone morphology, overlooking the informative potential of soft tissue attachment sites. In this study, we introduce a novel approach based on the three-dimensional geometric morphometric analysis of ligament insertion sites on the distal radial epiphysis. We analyzed a comparative sample including fossil hominins-Australopithecus afarensis, Australopithecus anamensis, Australopithecus sediba, Paranthropus robustus, Homo neanderthalensis, and archaic Homo sapiens-as well as extant hominoids: Homo sapiens, Pan troglodytes, Gorilla gorilla and Pongo pygmaeus. The results show marked interspecies differences in the size, orientation, and position of specific ligament insertions, reflecting divergent functional adaptations. Notably, the morphology of these insertions aligns with known behavioral and locomotor patterns described for these species, highlighting the reliability of ligament morphology as a proxy for inferring habitual activity in extinct taxa. This research expands the methodological toolkit available for paleoanthropology and emphasizes the relevance of soft-tissue-related structures in understanding hominin evolution beyond bone morphology alone.