Perimortem fractures in Lucy suggest mortality from fall out of tall tree

Journal name:
Nature
Volume:
537,
Pages:
503–507
Date published:
DOI:
doi:10.1038/nature19332
Received
Accepted
Published online

Abstract

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.

At a glance

Figures

  1. Perimortem fractures in A.L. 288-1 postcranial skeleton consistent with vertical deceleration event.
    Figure 1: Perimortem fractures in A.L. 288-1 postcranial skeleton consistent with vertical deceleration event.

    a, Lucy. b, c, Right humerus (b, top: stereo, superior, medial up; bottom: lateral; c, stereo, posterior) preserves valgus head-shattering four-part proximal fracture. d, Hinge and spiral fracture elevated, displaced, and fractured right midshaft humeral bone fragment (stereo, lateral; see b). e, Head of left humerus (stereo, medial) is fractured and compressed inferomedially to override the neck. f, Fracture of right distal radius (posterior, stereo view). g, Fractures in sacrum (stereo, anterior) and left innominate just lateral to sacrum. Fractured superior pubic ramus also visible as is puncture hole (arrow). h, Left-lateral asymmetry of fractured sacrum (stereo, posterior) and fractured, elevated, and bent retroauricular surface of left innominate. i, Left femoral neck fractures (stereo, lateral at top). j, Superoposteriorly fractured epiphysis of left distal femur (stereo, anterior) in discovery state with lateral extent sheared superiorly along lateral edge of shaft. Central portion of anterodistal shaft fractured and secondarily driven into trabeculae. k, Fracture of right tibial plateau (stereo, superior, medial to right) with major fracture across medial condyle that with other fractures (l; stereo, anterior, medial to right) depress the plateau and add valgus cant to shaft. m, Proximal portion of right distal tibia (stereo, posteromedial, superior at top) preserves small bone fragments broken loose and driven into medullary canal at spiral shaft fracture. n, Fractures on talar articular surface of right distal tibia (stereo, anterior, medial to right) open onto anterodistal surface of shaft. o, Right talus neck fracture (stereo, superior, medial to right). Together, n and o are consistent with a pilon fracture. Red lines are fractures; green lines in g, h denote sacroiliac joint and transverse lines of sacrum. Specimens in g and h are casts because it was not practical to articulate the fossils, and j is a cast because the original specimen was reconstructed. Scale bars (a, 50 mm; bf, io, 10 mm; g, h, 20 mm) are approximate, given stereo photo parallax. See Extended Data Figs 1, 2, 3, 4, Supplementary Note 1, and Supplementary Videos 1, 2, 3, 4.

  2. Reconstruction of Lucy’s vertical deceleration event.
    Figure 2: Reconstruction of Lucy’s vertical deceleration event.

    We hypothesize that Lucy fell from a tall tree, landing feet-first and twisting to the right, with arrows indicating the sequence and types of fractures. a, Pilon fracture, tibial plateau fracture, and spiral shaft fracture of right tibia. b, The impact of hyperextended left knee drove the distal femoral epiphysis into the distal shaft, and fractured the femoral neck and possibly the acetabulum, sacrum, and lumbar vertebra. c, The impact of the knee drove the patella into the centre anterodistal surface of the femoral shaft. d, Impact on the right hip drove the right innominate into the sacrum, and the sacrum into the left innominate, dislocating and fracturing the sacrum and left innominate, and elevating the retroauricular surface. e, Lucy was still conscious when she stretched out her arms in an attempt to break her fall and fractured both proximal humeri, the right more severely than the left with spiral fracture near the midshaft, a Colles’ (or Smith’s) fracture of the right radius, and perhaps other fractures of the radii and ulnae. The impact depressed and retracted the right scapula, which depressed the clavicle into the first rib, fracturing both. f, Frontal impact fractured the left pubis and drove a portion of the anterior inferior pubic ramus posterolaterally, and a branch or rock possibly created the puncture mark on the pubis. g, The impact of the thorax fractured many ribs and possibly some thoracic vertebrae. h, The impact of the skull, slightly left of centre, created a tripartite guardsman fracture of the mandible and cranial fractures. See Supplementary Methods and Supplementary Video 4.

  3. Right humerus (A.L. 288-1m) CT segmentation compared with photographs of fossil.
    Extended Data Fig. 1: Right humerus (A.L. 288-1m) CT segmentation compared with photographs of fossil.

    Right proximal humerus (A.L. 288-1m) illustrating the fractured fragments segmented from the CT scans compared with photographs of fossil. Nearly 30 fractured bone and articular head fragments and slivers were isolated by segmentation. Some small fragments remain embedded within the sediment on the posterior aspect of the head. One large fragment was avulsed off of the posteroinferior aspect of the articular head and not recovered. Scale bar, 10 mm. See Methods, Extended Data Fig. 2 and Supplementary Note 1 for a full description; also see Supplementary Video 1.

  4. Right humerus (A.L. 288-1m) CT segmentation with ‘before’ reconstruction and ‘after’ discovery state.
    Extended Data Fig. 2: Right humerus (A.L. 288-1m) CT segmentation with ‘before’ reconstruction and ‘after’ discovery state.

    Right proximal humerus (A.L. 288-1m) illustrating the head and diaphyseal shaft fragments segmented from the CT scans. The before image presents a reconstruction of the crushed proximal portion of the head that also straightens the spiral fracture at the diaphysis, and the after image shows the condition of the fossil in its discovery state. The impact compressed the proximal humerus against the glenoid of the scapula, with the glenoid acting as an anvil, which in turn fractured and shattered the components of the proximal humerus including the articular head, greater and lesser tuberosities, and shaft. Each pair of before and after images depicts the distal portion of the shaft in the same position and illustrates how the proximal portion of the head and shaft were angled in a posteromedial direction by the fracture. In some pairs of images the proximal end of the humerus is angled slightly towards the viewer to show a greater percentage of the head. Scale bar, 10 mm (approximate because of the differences in perspective). See Methods, Fig. 1, Extended Data Fig. 1 and Supplementary Note 1 for a full description; also see Supplementary Video 1.

  5. Mandible (A.L. 288-1i, -1j and -1k) photographs and CT scan.
    Extended Data Fig. 3: Mandible (A.L. 288-1i, -1j and -1k) photographs and CT scan.

    A comparison of photographs with CT scan of mandible (A.L. 288-1i, -1j and -1k) illustrating in red the major fractures across the parasymphyseal region, left body, and left (A.L. 288-1j) and right (A.L. 288-1k) subcondylar regions; and in green the fractures across the edges of the coronoid processes. The condyles were discovered and catalogued as separate specimens, and there is a set of closed fractures through the right condyle. Binding materials used in the reconstruction of the mandible are seen in yellow in the photographs, and as smooth dark brown in the CT scans. Note the generally tight contacts between adjacent bone fragments. Right p3–m3 teeth are complete whereas the anterior dentition and the teeth on the left side are fractured along the base of their crowns or are missing. This fracture pattern is typical of a tripartite guardsman fracture with fractures at parasymphysis and bilateral fractures in the subcondylar region. a, b, Left anterolateral view; c, d, right anterolateral view; e, f, superior view. Scale bars, approximately 10 mm because of angled views. See Supplementary Note 1 for a full description; also see Supplementary Videos 2, 3.

  6. Mandible (A.L. 288-1i, -1j and -1k) CT scan.
    Extended Data Fig. 4: Mandible (A.L. 288-1i, -1j and -1k) CT scan.

    CT scan of mandible (A.L. 288-1i, -1j and -1k) illustrating in red the major fractures across the parasymphyseal region, left body, and left (A.L. 288-1j) and right (A.L. 288-1k) subcondylar regions. The coronoid processes are missing and their fractured edges outlined in green. This fracture pattern is typical of a tripartite guardsman fracture with fractures at parasymphysis and bilateral fractures in the subcondylar region. a, Anterior view; b, posterior view; c, superior view; d, inferior view. eg, Anterior views of coronal slices: e, slice through the centre of canine alveolae that shows the major parasymphyseal fractures; f, slice at mesial edge of m3; and g, slice through mesial edge of coronoid process that shows the position of the right and left subcondylar fractures. Scale bar, 10 mm. See Supplementary Note 1 for a full description; also see Supplementary Videos 2, 3.

Tables

  1. Scan parameters for A.L. 288-1
    Extended Data Table 1: Scan parameters for A.L. 288-1

Videos

  1. Right humerus (A.L. 288-1m) and scapula (A.L. 288-1l) compressive fracture reconstruction
    Video 1: Right humerus (A.L. 288-1m) and scapula (A.L. 288-1l) compressive fracture reconstruction
    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.
  2. CT scan coronal slices of mandible (A.L. 288-1i, -1j  -1k)
    Video 2: CT scan coronal slices of mandible (A.L. 288-1i, -1j & -1k)
    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.
  3. CT scan sagittal slices of mandible (A.L. 288-1i, -1j  -1k)
    Video 3: CT scan sagittal slices of mandible (A.L. 288-1i, -1j & -1k)
    Caption as in Supplementary Video 2. Slices are in the sagittal plane.
  4. Lucy’s fall and vertical deceleration event
    Video 4: Lucy’s fall and vertical deceleration event
    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.

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Author information

Affiliations

  1. Department of Anthropology, The University of Texas at Austin, Austin, Texas 78712, USA

    • John Kappelman,
    • Lawrence Todd &
    • Adrienne Witzel
  2. Department of Geological Sciences, The University of Texas at Austin, Austin, Texas 78712, USA

    • John Kappelman,
    • Richard A. Ketcham,
    • Matthew W. Colbert &
    • Jessica A. Maisano
  3. Austin Bone and Joint Clinic, Austin, Texas 78705, USA

    • Stephen Pearce
  4. Department of Radio-Television-Film, The University of Texas at Austin, Austin, Texas 78712, USA

    • Wiley Akins
  5. Paleoanthropology and Paleoenvironment Program, Addis Ababa University, Addis Ababa, Ethiopia

    • Mulugeta Feseha

Contributions

J.K. conceived the project; J.K., R.A.K., S.P., L.T. and M.F. collected data; W.A., M.W.C., J.K. and A.W. completed the 3D reconstruction and video of the right humerus; and J.A.M. completed the 3D videos of the mandible. J.K. wrote the paper with comments from all authors.

Competing financial interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to:

Reviewer Information Nature thanks S. Black, W. Jungers and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Author details

Extended data figures and tables

Extended Data Figures

  1. Extended Data Figure 1: Right humerus (A.L. 288-1m) CT segmentation compared with photographs of fossil. (161 KB)

    Right proximal humerus (A.L. 288-1m) illustrating the fractured fragments segmented from the CT scans compared with photographs of fossil. Nearly 30 fractured bone and articular head fragments and slivers were isolated by segmentation. Some small fragments remain embedded within the sediment on the posterior aspect of the head. One large fragment was avulsed off of the posteroinferior aspect of the articular head and not recovered. Scale bar, 10 mm. See Methods, Extended Data Fig. 2 and Supplementary Note 1 for a full description; also see Supplementary Video 1.

  2. Extended Data Figure 2: Right humerus (A.L. 288-1m) CT segmentation with ‘before’ reconstruction and ‘after’ discovery state. (386 KB)

    Right proximal humerus (A.L. 288-1m) illustrating the head and diaphyseal shaft fragments segmented from the CT scans. The before image presents a reconstruction of the crushed proximal portion of the head that also straightens the spiral fracture at the diaphysis, and the after image shows the condition of the fossil in its discovery state. The impact compressed the proximal humerus against the glenoid of the scapula, with the glenoid acting as an anvil, which in turn fractured and shattered the components of the proximal humerus including the articular head, greater and lesser tuberosities, and shaft. Each pair of before and after images depicts the distal portion of the shaft in the same position and illustrates how the proximal portion of the head and shaft were angled in a posteromedial direction by the fracture. In some pairs of images the proximal end of the humerus is angled slightly towards the viewer to show a greater percentage of the head. Scale bar, 10 mm (approximate because of the differences in perspective). See Methods, Fig. 1, Extended Data Fig. 1 and Supplementary Note 1 for a full description; also see Supplementary Video 1.

  3. Extended Data Figure 3: Mandible (A.L. 288-1i, -1j and -1k) photographs and CT scan. (443 KB)

    A comparison of photographs with CT scan of mandible (A.L. 288-1i, -1j and -1k) illustrating in red the major fractures across the parasymphyseal region, left body, and left (A.L. 288-1j) and right (A.L. 288-1k) subcondylar regions; and in green the fractures across the edges of the coronoid processes. The condyles were discovered and catalogued as separate specimens, and there is a set of closed fractures through the right condyle. Binding materials used in the reconstruction of the mandible are seen in yellow in the photographs, and as smooth dark brown in the CT scans. Note the generally tight contacts between adjacent bone fragments. Right p3–m3 teeth are complete whereas the anterior dentition and the teeth on the left side are fractured along the base of their crowns or are missing. This fracture pattern is typical of a tripartite guardsman fracture with fractures at parasymphysis and bilateral fractures in the subcondylar region. a, b, Left anterolateral view; c, d, right anterolateral view; e, f, superior view. Scale bars, approximately 10 mm because of angled views. See Supplementary Note 1 for a full description; also see Supplementary Videos 2, 3.

  4. Extended Data Figure 4: Mandible (A.L. 288-1i, -1j and -1k) CT scan. (215 KB)

    CT scan of mandible (A.L. 288-1i, -1j and -1k) illustrating in red the major fractures across the parasymphyseal region, left body, and left (A.L. 288-1j) and right (A.L. 288-1k) subcondylar regions. The coronoid processes are missing and their fractured edges outlined in green. This fracture pattern is typical of a tripartite guardsman fracture with fractures at parasymphysis and bilateral fractures in the subcondylar region. a, Anterior view; b, posterior view; c, superior view; d, inferior view. eg, Anterior views of coronal slices: e, slice through the centre of canine alveolae that shows the major parasymphyseal fractures; f, slice at mesial edge of m3; and g, slice through mesial edge of coronoid process that shows the position of the right and left subcondylar fractures. Scale bar, 10 mm. See Supplementary Note 1 for a full description; also see Supplementary Videos 2, 3.

Extended Data Tables

  1. Extended Data Table 1: Scan parameters for A.L. 288-1 (96 KB)

Supplementary information

Video

  1. Video 1: Right humerus (A.L. 288-1m) and scapula (A.L. 288-1l) compressive fracture reconstruction (30.46 MB, Download)
    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.
  2. Video 2: CT scan coronal slices of mandible (A.L. 288-1i, -1j & -1k) (19.35 MB, Download)
    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.
  3. Video 3: CT scan sagittal slices of mandible (A.L. 288-1i, -1j & -1k) (16.22 MB, Download)
    Caption as in Supplementary Video 2. Slices are in the sagittal plane.
  4. Video 4: Lucy’s fall and vertical deceleration event (20.09 MB, Download)
    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.

PDF files

  1. Supplementary Information (1.1 MB)

    This file contains Supplementary Notes 1-8, Supplementary References and Supplementary Methods. Please note a set of 3D.stl files of the right shoulder and left knee are available for download at www.eLucy.org.

Comments

  1. Report this comment #68825

    Panos Stamoulis said:

    This is an exciting and interesting article, but – without being a specialist in any of the relevant fields- I find the conclusions too far fetched. Maybe I am reading the sketch of the fall too literally, but
    -I think nobody falls 'straight down' from a big height when climbing a tree(?).
    -The breaking of both the legs, the pelvis and hand bones, and bones in the thorax, should 'break' the fall enough for the head not to hit too hard(?).
    Also, a very tall, straight tree in a rocky stream bed seems to me quite a stretch.
    Of course, i cannot really substantiate any of the above with hard data, and do not have access to references 16,17 30 that the authors use to corroborate the bone breaking sequence in analogy to human fall victims.

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