Associated cranial and forelimb remains attributed to
Australopithecus afarensis from Hadar, Ethiopia
M.S.M. Drapeau
a,
*
, C.V. Ward
b
, W.H. Kimbel
c
, D.C. Johanson
c
, Y. Rak
d
a
De´partement d’anthropologie, Universite´ de Montre´al, C.P. 6128, succursale Centre-ville, Montre´al QC H3C 3J7, Canada
b
Department of Anthropology, Department of Pathology and Anatomical Sciences, Swallow Hall,
University of Missouri, Columbia, MO 65211, USA
c
Institute of Human Origins and Arizona State University, P.O. Box 874101, Tempe, AZ 85287, USA
d
Department of Anatomy, Sackler Faculty of Medicine, Tel Aviv University/Ramat-Aviv, Tel Aviv, 69978, Israel
Received 13 October 2003; accepted 18 February 2005
Abstract
A partial skeleton from Hadar, Ethiopia (A.L. 438-1) attributed to Australopithecus afarensis is comprised of part of
the mandible, a frontal bone fragment, a complete left ulna, two second metacarpals, one third metacarpal, plus parts of
the clavicle, humerus, radius, and right ulna. It is one of only a few early hominin specimens to preserve both cranial and
postcranial elements. It also includes the first complete ulna from a large A. afarensis individual, and the first associated
metacarpal and forelimb remains. This specimen, dated to approximately 3 Ma, is among the geologically youngest
A. afarensis fossils and is also one of the largest individuals known. Its ulnar to mandibular proportions are similar to
those of the geologically older and much smaller A.L. 288-1, suggesting that body size increased without disproportional
enlargement of the mandible. Overall, however, analysis of this large specimen and of the diminutive A.L. 288-1
demonstrates that the functional morphology of the A. afarensis upper limb was similar at all body sizes; there is no
evidence to support the hypothesis that more than one hominin species is present at Hadar. Morphologically, all
apparent apomorphic traits of the elbow, forearm, wrist, and hand of A.L. 438-1 are shared uniquely with humans.
Compared to humans, A.L. 438-1 does have a more curved ulna, although A.L. 288-1 does not, and it appears to have
had slightly less well-developed manipulatory capabilities of its hands, although still more derived than in apes. We
conclude that selection for effective arboreality in the upper limb of Australopithecus afarensis was weaker than in non-
hominins, and that manipulative ability was of greater selective advantage than in extant great apes.

2005 Elsevier Ltd. All rights reserved.
Keywords: Australopithecus afarensis; forelimb; ulna; metacarpals; proportions
Journal of Human Evolution 48 (2005) 593e642* Corresponding author.
E-mail addresses: m.drapeau@umontreal.ca (M.S.M. Drapeau), wardcv@missouri.edu (C.V. Ward), wkimbel.iho@asu.edu (W.H.
Kimbel), johanson.iho@asu.edu (D.C. Johanson), yoelrak@post.tau.ac.il (Y. Rak).
0047-2484/$ - see front matter
2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.jhevol.2005.02.005

Introduction
In 1994, Kimbel and colleagues announced the
discovery of a partial skeleton from Hadar,
Ethiopia, attributed to Australopithecus afarensis
(Fig. 1). This specimen, A.L. 438-1, is from the
Kada Hadar member, situated stratigraphically
approximately 12 m below the BKT-2 tuff, which
has been dated to 2.94 Ma (Kimbel et al., 1994;
Semaw et al., 1997). It is thus approximately 3
million years old, equivalent in age to the adult
male skull A.L. 444-2 (Kimbel et al., 2004). The
A.L. 438-1 specimen preserves part of the mandi-
ble, a few small maxillary bits, a frontal bone
fragment, a complete left ulna, two second
metacarpals, one third metacarpal, plus a part of
the clavicle, humerus, radius and right ulna.
The A.L. 438-1 specimen is significant for
a number of reasons. It preserves both craniofacial
and postcranial remains, affording an opportunity
not only to compare intraskeletal cranial and
postcranial proportions in A. afarensis, but also
to compare two individuals attributed to that
species, the other being the partial skeleton A.L.
288-1 (‘‘Lucy’’). While A.L. 288-1 is one of the
smallest known A. afarensis individuals, A.L. 438-1
is among the largest. This size discrepancy between
A.L. 438-1 and A.L. 288-1 provides an opportunity
to test the hypothesis that two morphologically
distinct species, one large and one small, are present
at Hadar (e.g. Johanson and Taieb, 1976; Olson,
1981, 1985; Ferguson, 1983, 1984; Senut and
Tardieu, 1985; Zihlman, 1985; Schmid, 1989; Senut,
1996, 1999) by comparing the proportions and
morphology of these specimens. The A.L. 438-1
skeleton also provides the first complete ulna of
A. afarensis, and the first from a large individual.
The only other nearly complete ulna belongs to
A.L. 288-1 (Johanson et al., 1982). Because theA.L.
438-1 ulna is comparable in size to at least two
others tentatively attributable to Australopithecus
sensu lato, L40-19 from the Omo valley (Howell
and Wood, 1974; Howell and Coppens, 1976;
McHenry et al., 1976; Howell et al., 1987) and OH
36 from Olduvai Gorge (Leakey, 1978; Day, 1986;
Tobias, 1991)(Fig. 2), A.L. 438-1 permits the
comparison of A. afarensis to these specimens with
594 M.S.M. Drapeau et al. / Journal of Ha minimum of confounding allometric effects.The A.L. 438-1 specimen is also the first A.
afarensis fossil to include metacarpals associated
with forearm elements. Because forelimb propor-
tions are relevant to discussions of forelimb
function and behavioral adaptations, this discov-
ery stands to add important information to our
understanding of forelimb functional anatomy in
early hominins.
In this paper, we provide detailed anatomical
descriptions of the postcranial elements of this new
specimen. The frontal fragment and mandible are
described in detail elsewhere (Kimbel et al., 2004;
C. Robinson et al., in prep.). We also put these
postcranial bones into evolutionary context by
comparing their morphology and proportions to
those of extant and fossil hominoids.
Recovery and context
All of the elements attributed to A.L. 438-1 are
very well preserved, bear mostly sharp, fresh
breaks, and are buff colored with occasional gray
to yellow mottling. The first fragments recovered
(by D. Johanson on 24 February 1992) were
surface finds of the left proximal ulna, two left
metacarpals, a segment of humeral shaft, and the
frontal fragment. During a sweep of the surface,
additional hominin fragments were recovered:
several ulnar and radial shaft portions, including
a left ulnar fragment that articulates with the
initially discovered piece to make up the proximal
half of the bone; a right metacarpal; a small
maxillary fragment with tooth roots; and a partial
right mandible with M
2
and M
3
crowns.
Subsequent excavation of 52 m
2
to a depth of
up to 53 cm resulted in the recovery of several in
situ fragments that can be associated with the
surface finds. Two distal fragments and associated
shaft splinters of the left ulna were excavated in
situ a few meters from the surface finds. The
fragments were discovered within 3 cm of each
other, and articulate to produce the distal shaft
and epiphysis of the left ulna. These pieces
together articulate along a planar, lightly weath-
ered shaft break with the two proximal portions
recovered on the surface to produce the virtually
uman Evolution 48 (2005) 593e642complete left ulna.