The Pliocene fossil ‘Lucy’ (Australopithecus afarensis) was discovered in the Afar region of Ethiopia in 1974 and is among the oldest and most complete fossil hominin skeletons discovered. Here we propose, on the basis of close study of her skeleton, that her cause of death was a vertical deceleration event or impact following a fall from considerable height that produced compressive and hinge (greenstick) fractures in multiple skeletal elements. Impacts that are so severe as to cause concomitant fractures usually also damage internal organs; together, these injuries are hypothesized to have caused her death. Lucy has been at the centre of a vigorous debate about the role, if any, of arboreal locomotion in early human evolution. It is therefore ironic that her death can be attributed to injuries resulting from a fall, probably out of a tall tree, thus offering unusual evidence for the presence of arborealism in this species.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
We thank the Authority for Research and Conservation of Cultural Heritage and the National Museum of Ethiopia of the Ministry of Tourism and Culture for permission to scan, study, and photograph Lucy; A. Admassu, K. Ayele, J. A. Bartsch, Y. Beyene, Y. Desta, R. Diehl, R. Flores, R. Harvey, G. Kebede, R. Lariviere, J. H. Mariam, S. M. Miller, L. Rebori, B. Roberts, J. Ten Barge, J. M. Sanchez, D. Slesnick, D. Van Tuerenhout, S. Wilson, M. Woldehan, and M. Yilma for facilitating and assisting with the scanning; T. Getachew and M. Endalamaw for assisting with the photography, and S. Mattox for many of the photographs; V. A. Lopez and S. Robertson for Fig. 2; C. Bramblett, B. Brown, C. Campisano, J. G. Fleagle, T. Helpenstell and colleagues at Olympia Orthopaedic Associates, A. L. Kappelman, J. A. Kappelman, S. Khosropour, H. Pontzer, D. Reed, C. B. Ruff, J. T. Stern Jr, and S. C. Ward for discussions; the Paleoanthropology Laboratory Fund, College of Liberal Arts UT Austin, and Houston Museum of Natural Science for financial and logistical support; and Owen-Coates Fund of the Geology Foundation of UT Austin for publication costs. The University of Texas High-Resolution X-ray CT Facility was supported by US National Science Foundation grants EAR-0646848, EAR-0948842, and EAR-1258878.
Extended data figures
Extended data tables
Video of hypothetical impact scenario for the right humerus and scapula that illustrates the progression of the fracture. The "before" reconstruction of the humerus is seen in the first full rotation. Next, the fragments are colorized and the humerus is impacted into the anvil of the glenoid of the scapula, fracturing and shattering the components of the proximal humerus including the articular head, greater and lesser tuberosities, and shaft. Finally, the "after" condition is shown in the last rotation. See Methods, Extended Data Figures 1 & 2, Supplementary Note 2 for a description of the reconstruction, and Supplementary Video 4.
Video of CT scan (see Methods) of the original reconstruction of the mandible illustrates the fractures across the mandible and especially those in the parasymphyseal region, left body, and subcondylar regions. Slices are in the coronal plane. The smooth dark brown regions are binding materials used in the reconstruction. This fracture pattern is typical of a tripartite guardsman fracture. See Extended Data Figures 3 & 4 for the location of the fractures, and Supplementary Note 1 for a full description.
Caption as in Supplementary Video 2. Slices are in the sagittal plane.
Stop motion video depicts a hypothetical scenario for Lucy’s fall out of a tall tree and the subsequent vertical deceleration event based on the patterning of the fractures. The first segment depicts about the last half of the fall from 7.4 m with a real time duration of 0.45 seconds, and the second segment shows a close-up of the last 2.2 m of the fall. The third segment shows a slow-motion (about 1/5 speed) close-up of the last 1.7 m of the fall. The last frame illustrates the fractures. See Figure 2 for a full description.
About this article
The torso integration hypothesis revisited in Homo sapiens : Contributions to the understanding of hominin body shape evolution
American Journal of Physical Anthropology (2018)