Research Instructor
Department of Anatomical Sciences
Stony Brook University
I hold a PhD in anthropology from Arizona State University where I worked closely with the Institute of Human Origins . I am a broadly trained biological anthropologist with specific research and teaching interests in paleoanthropology, primate evolution, and comparative anatomy.
My work primarily focuses on the functional morphology of the postcranial skeleton in extant primates and fossil hominins (human ancestors) with special emphasis on the hands and feet and its relevance to understanding the origins of human bipedality, manual manipulative capabilities and tool use.
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RESEARCH OVERVIEW
As a paleoanthropologist and evolutionary anatomist, I am interested in understanding the adaptations and phylogenetic relationships of our early ancestors and the sequence, timing and causes of key events in human biological and cultural evolution. In particular, habitual bipedality and the intensification of tool behaviors represent two of the key adaptive signatures of the human lineage, and explaining their origins has long been a focus of inquiry. The evolutionary histories of these adaptations are intertwined due to the emancipation of the forelimb granted by upright posture; thus, I have focused most of my attention on the morphology of the hands and feet in humans and nonhuman primates and fossil hominins (early human ancestors). Understanding the evolutionary transformation of the postcranial skeleton in the human lineage requires 1) reconstructing the mode of locomotion (and mechanical demands on the skeleton) that preceded the origins of bipedality; 2) revealing constraints imposed by that ancestral condition; and 3) identifying subsequent morphological changes and their functional significance for novel behaviors (for example, adaptations of the hominin hand to tool making and use). Most of my projects tackle aspects of this research agenda.
I address these questions by way of traditional anatomical study of bones, fossils, and cadaveric material coupled with quantitative bioengineering and computer science approaches. These methods include computed-tomography-based carpal kinematic analysis, surface laser scanning and three-dimensional morphometrics , electromyography , measurement of muscle moment arms, and broad-based comparative studies of primates and nonprimate mammals. Paleoanthropological field work has taken me to Ethiopia, France, and Spain.
Genetic data indicate that chimpanzees and humans share a closer common ancestor than either does with gorillas or orangutans. The African apes [chimps (genus Pan ) and gorillas (genus Gorilla )] are both terrestrial knuckle-walkers; thus, either the last common ancestor of humans and Pan was a knuckle-walker, or this behavior and its anatomical adaptations must have evolved independently in Pan and Gorilla . Resolving this issue is crucial for understanding the origins of bipedality and enhanced manipulation, but is dependent on the accurate functional interpretation of the anatomy in relation to hand posture. To test hypotheses involving purported knuckle-walking features of African apes and hominins I have adopted a broad comparative approach using the knuckle-walking giant anteater as an analogue (Orr, 2005) and conducted rigorous biomechanical and morphometric analyses of the anthropoid primate wrist (Orr, 2010; Orr et al., 2008, 2009, 2010). These studies have included the novel application of 3D kinematic analyses to understand wrist mechanics in nonhuman primates.
If hominins derived from a knuckle-walking ancestor, then we must explain the evolution of bipedality in a primate already well-suited for life on the ground. Furthermore, knuckle-walkers have rigid hands and wrists that permit use of the forelimbs as rigid support struts during propulsion (in contrast to the more mobile wrists of arboreal apes and monkeys). Thus, if the early hominin forelimb was adapted for such terrestrial use, then overcoming the constraints imposed on hand mobility may have been necessary during the evolution of more sophisticated manual manipulation. My work on the wrist shows that some features of the African apes previously levied to support the knuckle-walking ancestor hypothesis do not function as thought. Nevertheless, a few characteristics are consistent with a knuckle-walking adaptive complex and these are variably present in hominins (e.g., fusion of two bonesthe scaphoid and centralis characteristic of Pan , Gorilla , and all hominins, and plays a key role in producing wrist stability). However, the interpretation of these features has become further complicated by recent reports on the postcranial anatomy of Ardipithecus ramidus, and investigation of the hand and wrist anatomy of this taxon is currently underway (see here) .
Funding: National Science Foundation doctoral dissertation improvement grant (BCS-622515), Wenner-Gren Dissertation Field Work grant, Sigma Xi Grant-in-Aid of Research, and Arizona State University
PROJECTS
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Other projects have included:
- comparative functional analysis of the tarsus in relation to the ecological divergence of the various gorilla taxa to better understand the relationship between foot morphology and the use of arboreal versus terrestrial substrates in large-bodied hominoids (with Matt Tocheri , Bill Jungers and others).
- electromyographic monitoring of muscle activity during simulated flintknapping of Oldowan tools to test hypotheses about the evolution of elbow function and manipulative capabilities in hominins
- measuring triceps muscle mechanical advantage in relation to habitual forelimb position in primates including humans
- evaluating claims for the existence of venom delivery systems in Cretaceous mammals
CARPAL KINEMATIC VIDEOS
These videos were made by adapting a three-dimensional computed-tomography-based technique developed for orthopaedics to track wrist bone motion in primate cadavers manipulated with an experimental jig (Orr et al., 2010). The work was done in collaboration with bioengineers from Dr. Trey Crisco's lab at Brown Medical School and Rhode Island Hospital, Dr. Scott Wolfe from the Hospital for Special Surgery at Cornell's Weill Medical College, and Dr. Spencer Chivers from the Mayo Clinic. Funding was provided by the National Science Foundation and the Wenner-Gren Foundation for Anthropological Research.
Top : Radiocarpal and midcarpal kinematics in a chimpanzee ( Pan troglodytes ). Early midcarpal engagement is evident in the "locking up" of the lunate (light blue) and scaphoid (red) with the capitate midway through total wrist motion. This provides for a rigid wrist, which facilitates the use of the hand as a propulsive lever during knuckle-walking.
Bottom: Fusion of the os centrale to the scaphoid is a derived feature that humans share with chimpanzees and gorillas, and understanding its function is important for reconstructing the evolutionary history of the human hand. This video demonstrates the kinematics of a free centrale (pale green) in an orangutan ( Pongo pygmaeus ) viewed relative to a fixed scaphoid (light blue). Independent motion of the centrale is evident in all motion planes. This supports the hypothesis that fusion of the centrale to the scaphoid in the African apes and hominins contributes to early midcarpal engagement seen above and increased wrist rigidity compared to the primitive state (a free centrale) exhibited by most nonhuman primates.
PUBLICATIONS
Peer reviewed articles:
2011 Tocheri MW, Solhan CR, Orr CM , Femiani J, Frohlich B, Groves CP, Harcourt-Smith W, Richmond BG, Shoelson B, Jungers WL. Ecological divergence and medial cuneiform morphology in gorillas. Journal of Human Evolution 60:171-184.
2010 Orr CM, Leventhal EL, Chivers SF, Marzke MW, Wolfe SW, Crisco JJ. Studying primate carpal kinematics in three-dimensions using a computed-tomography-based markerless registration method. The Anatomical Record 293:692-709. -Invited paper for a special issue on primate functional morphology
2010 Marzke MW, Tocheri MW, Steinburg B, Femiani JD, Linscheid RL, Orr CM , Marzke RF. Comparative 3D quantitative analyses of trapeziometacarpal joint surface curvatures among living catarrhines and fossil hominins. American Journal of Physical Anthropology 141:38-51.
2009 Larson SG, Jungers WL, Tocheri MW, Orr CM , Morwood MJ, Sutikna T, Awe Due R, Djubiantono T. Descriptions of the upper limb skeleton of Homo floresiensis . Journal of Human Evolution 57:555-570.
2008 Tocheri MW, Orr CM, Jacofsky MC, Marzke MW. The evolutionary history of the hominin hand since the last common ancestor of Pan and Homo. Journal of Anatomy 212:544-562.
2007 Tocheri MW, Orr CM , Larson SG, Sutikna T, Jatmiko, Saptomo EW, Awe Due R, Djubiantono T, Moorewood MJ, Jungers WL. The primitive wrist of Homo floresiensis and its implications for hominin evolution. Science 317:1743-1745.
-This paper was recognized with a 2007 Science Achievement Award by the Smithsonian Institution
2007 Orr CM , Delezene LK, Scott JE, Tocheri MW, Schwartz GT. The comparative method and the inference of venom delivery systems in fossil mammals. Journal of Vertebrate Paleontology 27:541-546.
2006 Wolfe SW, Crisco JJ, Orr CM , Marzke MW. The dart-thrower’s motion of the wrist: is it unique to humans? The Journal of Hand Surgery 31:1429-1437.
2005 Orr CM . The knuckle-walking anteater: a convergence test of adaptation for purported knuckle-walking features of African Hominidae. American Journal of Physical Anthropology 128:639-658
2001 Orr CM , Dufour DL, Patton JQ. A comparison of anthropometric indices of nutritional status in Tukanoan and Achuar Amerindians. The American Journal of Human Biology 13:301-30
Orr et al 2010.pdf
Marzke et al 2010.pdf
Larson et al 2009.pdf
Tocheri_et_al_2008_J_ANAT.pdf
Tocheri_et_al_2007.pdf
Orr_et_al_2007.pdf
Wolfe et al. 2006.pdf
Orr_KW_anteater_2005.pdf
Orr_et_al_2001.pdf
CURRICULUM VITAE
DOWNLOAD FULL CV
Education
2010 Ph.D. Anthropology, School of Human Evolution and Social Change, Arizona State University
Dissertation title: “Adaptations to Knuckle-Walking and Digitigrady: A Three-Dimensional Kinematic and
Morphometric Analysis of the Anthropoid Wrist”
Committee co-chairs: Mary Marzke and Mark Spencer
Committee members: William Kimbel (Arizona State) and Carol Ward (University of Missouri)
2003 M.A. Anthropology. Arizona State University
2000 B.A. Anthropology (minor in Biology), University of Colorado at Boulder.
Summa cum Laude with Distinction
Academic Positions Held
2010-present Research Instructor, Department of Anatomical Sciences, Stony Brook University, Stony Brook, NY
2010 (6 months) Postdoctoral Fellow, Human Origins Program, Department of Anthropology,
National Museum of Natural History, Smithsonian Institution, Washington, DC
2009-2010 Adjunct Professor, School of Human Evolution and Social Change, Arizona State University
2007-2008 Graduate Teaching Assistant, University of Arizona College of Medicine-Phoenix
and School of Human Evolution and Social Change, Arizona State University
2004 Adjunct Professor, Mesa Community College, Mesa Arizona
Orr_CV.pdf
TEACHING
I have experience teaching in both biological anthropology and the anatomical sciences. See my CV for a detailed list.
ORR-intro-to-physical-anthropology.pdf
ORR-Paleoanthropology-syllabus.pdf
ORR-Natural-history-of-culture.pdf
Spencer-and-Orr-comparative-anatomy.pdf
ORR-sample-lab-in-primate-adaptation.pdf
CONTACT
Caley M. Orr
Health Sciences Center
Stony Brook, NY 11794-8081
email : caley (dot) orr (at) gmail (dot) com
fax : 631-444-3947
Image of Ardipithecus ramidus hand from Lovejoy, C. O., S. W. Simpson, T. D. White, B. Asfaw, and G. Suwa. 2009. Careful climbing in the Miocene: the forelimbs of Ardipithecus ramidus and humans are primitive. Science 326:70e1-70e8.
The fossil species Ardipithecus ramidus from the site of Aramis, Ethiopia dates to 4.4 million years ago and may be one of the oldest hominins. Thus, it holds potentially crucial clues about the last common ancestor of Homo sapiens and the African apes. A number of features of the teeth, cranium, and pelvis in Ar. ramidus suggest that it is a member of the human branch of the phylogenetic tree. However, the postcranial body plan of Ar. ramidus has been described as less extant-ape-like than expected-- apparently resembling the more generalized quadrupedal and careful-climbing anatomy of earlier apes such as Proconsul . An important aspect of this reconstruction involves hand function, which some (Lovejoy et al., 2009) have argued indicates the use of palmigrady (i.e., a weight-bearing palm with an extended wrist, which is adaptive for careful above-branch arboreal locomotion). If Ardipithecus is truly a hominin, then this locomotor reconstruction indicates that the shared adaptations of all extant great apes to vertical climbing, suspension (and knuckle-walking in chimps and gorillas) may have evolved independently. This is a dramatic departure from expectations based on 150 years of anatomical study, and it holds important consequences for understanding the evolution of bipedality as well as modifications to improve the performance of tool behaviors. For example, some characteristics that would suggest palmigrady (e.g., a mobile wrist and pliable palm) may also be biomechanical prerequisites for the highly developed manual manipulative capabilities of humans, indicating that later hominins simply co-opted primitive features to facilitate tool behaviors, rather than having evolved them via natural selection specifically for such tasks. These implications have led some to hypothesize instead that Ardipithecus is not a hominin and that its lineage diverged prior to the split between African apes and humans.
Research on the hand and wrist in Ar. ramidus and comparison with Miocene apes is among my top priorities. The objective is to test the hypotheses that 1) Ar. ramidus is a hominin; and 2) it made use of palmigrade hand postures that differed from the role of the forelimb in advanced vertical climbing, suspension, and/or knuckle-walking as exhibited by the extant ape species. This work is in its initial stages, and my collaborators and I were hosted by Dr. Tim White in the Human Evolution Research Center at the University of California-Berkeley in September 2010 to examine casts for preliminary study. Careful analysis of the Ar. ramidus material is critical to advancing the field of paleoanthropology, and our work will contribute in significant ways to the interpretation of these important specimens and their implications for understanding the biology and evolution of our earliest ancestors.
Funding: The Wenner-Gren Foundation for Anthropological Research and the Leakey Foundation.
In addition to working on the earliest stages of human evolution, I have been collaborating on analyses of the hand and foot remains associated with the diminutive fossil species Homo floresiensis (the so-called "Hobbit") from the late Pleistocene of Indonesia. These remains have attracted intense scientific and public interest due to their late date (~18,000 years old for the type specimen), apparently primitive morphology, and a tiny body size (~1 m in height) initially explained as a possible case of island dwarfing in a hominin species. Our first analysis on the wrist anatomy (published in the journal Science) demonstrated that derived features shared by modern humans and Neandertals are absent, and showed that the Flores wrist is instead reminiscent of Australopithecus and the African apes (Tocheri, Orr, et al., 2007, 2008; Larson et al., 2009). Although the origins of H. floresiensis remain uncertain, our work stands among the most definitive evidence that the Flores material represents an ancient hominin lineage. Furthermore, because H. floresiensis is associated with stone tools, the results provide insight into the relationship between hand anatomy and tool behavior. Currently, I am describing and analyzing new, unpublished wrist bones from a second individual (Orr et al. meeting abstract in review and manuscript in preparation) as well as studying ankle morphology. To support these studies, I have been a co-PI on grants with colleagues at the Smithsonian Institution, American Museum of Natural History, and Stony Brook University, and in coming years expect to collaborate on field work in Indonesia to address outstanding questions about the biology and cultural adaptations of H. floresiensis .
Funding: Smithsonian Institution Postdoctoral Research Fellowship to C.M. Orr, a Smithsonian Institution Scholarly Studies grant (PI: MW Tocheri), and a Wenner-Gren Foundation Post-PhD research grant (PI: M.W. Tocheri ; co-PIs: W. Harcourt-Smith , W.L. Jungers , and C.M. Orr, co-primary investigators).
