3D volumetric muscle reconstruction of theAustralopithecus afarensispelvis and limb, with estimations of limb leverage

Abstract

AbstractTo understand how an extinct species may have moved, we first need to reconstruct the missing soft tissues of the skeleton which rarely preserve, with an understanding of segmental volume and the muscular composition within the body. TheAustralopithecus afarensisspecimen AL 288-1 is one of the most complete hominin skeletons. Whilst it is generally accepted that this species walked with an erect limb, the frequency and efficiency of such movement is still debated. Here, 36 muscles of the pelvis and lower limb were reconstructed in the specimen AL 288-1 using 3D polygonal modelling which was guided by imaging scan data and muscle scarring. Reconstructed muscle masses and configurations guided biomechanical modelling of the lower limb in comparison to a modern human. Muscle moment arms were calculated and summed per muscle group. Simulated error margins were computed using Monte Carlo analyses. Results show that the moment arms of both species were comparable, hinting towards similar limb functionality. Moving forward, the polygonal muscle modelling approach has demonstrated promise for reconstructing the soft tissues of hominins and providing information on muscle configuration and space filling. This approach is recommended for future studies aiming to model musculature in extinct taxa.