Caley Orr

@caleyorr.bsky.social

1748 Followers 828 Following

Associate Professor | CU School of Medicine & CU Denver Anthropology | Paleoanthropology, Primate Morphology, Teaching Anatomy, Noisy Rock & Roll, Felis catus | Research: ucdenver.academia.edu/CaleyOrr

Figure 2 from Monson et al (2026). Figure 2. Allometric scaling of endocranial volume and body mass in extant primates and Plio-Pleistocene hominids. The figure displays a bivariate plot with two regression slopes through known fossil hominin species and the extant apes. It shows that the early hominin species Ardipithecus ramidus and Australopithecus anamensis may have had a relationship between body mass and endocranial volume (a proxy for brain size) more similar to extant apes with relatively small brains. In contrast, hominins after 3 million years ago show larger endocranial volumes relative to their inferred body mass.
Phylogenetic tree showing the evolutionary relationships of living and fossil apes including the newly described fossil Masripithecus moghraensis.
A custom skateboard deck designed by Caley Orr ("Orrigins Skateboards") with a 3D rendered image (from a CT scan) of a chimpanzee hand raised in the punk rock defiance of our troubled times (and in palmar view). The featured primate's common name is printed at the nose of the board and the Linnean binomen is printed at the tail in a font reminiscent of the lettering of the band's name on The Cramps classic 1980 debut psychobilly album "Songs the Lord Taught Us." "ORRIGINS" and "AABA Denver 2026" are printed in the posterior truck-mount square to commemorate the big bioanth party. The board is football shaped (similar to skateboards popular in the early to mid-1990s). It measures 32 inches in rostrocaudal length, 8.87 inches in maximum mediolateral width, with a 7 inch nose, 7 inch tail, and 14 inch wheelbase. The tail tapers slightly to its apex and the deck has a shallow dorsal concavity. I apologize to my colleagues that the dimensions aren't in metric. It goes against my scientific sensibilities, but American skateboarders are still hooked on the Imperial system. Thrash on.
Figure 1 from Blasi-Toccacceli et al. Views of OMO VE3-10063. Humerus OMOVE3-10063a, proximal portion: A,lateral; B,anterior; C,medial, D,posterior; E,proximal. Humerus OMOVE3-10063a, diaphysis: F,lateral; G,anterior; H,medial;I,posterior. Humerus OMOVE3-10063a, distalportion: J, Anterior; K, posterior; L,distal.Clavicle OMOVE3-10063c: M, Proximal; N, posterior; O, distal; P,a nterior. Scapula OMO-VE 3-10063b: Q, Anterior; R, posterior; S, lateral. Cervical neural arch OMOVE3-10063d: T, Superior; U, inferior. Cervical body OMOVE3-10063e: V,Anterior; W,posterior;X,inferior;Y,superior. RibOMOVE3-10063f: Z-superior ; a,inferior. See the detailed description of the individual in the Supplementary Material (Supplementary Text “Description of OMO VE 3-10063”) and Table S1. Abbreviations: Prox.: proximal; Dist.: distal; Med.: medial; Lat.: lateral; Post.: posterior; Ant.: anterior.
Figure 2 from Orr et al 2026. Arm and forearm elements including an adult distal humerus (a), proximal ulna probably from a subadult (b), fetal/perinatal humeri (c), and fetal/perinatal radii (d). Based on spatial context and developmental age, DNH 110 might be associated with DNH 112 (proximal tibia).
Figure 15 from Orr et al 2026. Comparative analyses of the DNH 117 nonhallucal pedal proximal phalanx. (a) Bivariate ln-ln plot of the midshaft area calculated as the mediolateral width (ML) × dorsoplantar height (DP) against interarticular length; sample includes recent H. sapiens (open triangles), Pan sp. (black plus signs), Gorilla sp. (open circles); Pleistocene H. sapiens (filled black triangles); Neandertals (open triangles); H. naledi (blue triangles); A. afarensis (red squares); P. boisei KNM-ER 101000 (green square); Swartkrans specimen SKX 16699 (green diamond), A. cf. africanus StW 355 (yellow square); DNH 117 (yellow star). Because ray is unknown for most of the fossil specimens, the extant sample combines all rays II–V. Least-squares regression line fit to full extant sample (ln midshaft area = 1.87 × ln midshaft area − 2.58). (b) Dorsal orientation of the metacarpophalangeal joint facet quantified as the articular angle following Trinkaus and Patel (2016) with comparative data from the same source; (c) longitudinal shaft curvature quantified as the included angle following Stern Jr. et al. (1995). (d) 3D surface renderings of DNH 117 and select comparative specimens in plantar view (top) and “lateral” view (bottom). Images of all specimens are scaled to the same proximodistal length. Plots b and c include the median of the sample along with the interquartile range (box) and the full range (whiskers).
Figure 10 from Orr et al 2026. Shape analysis of the DNH 32 distal humerus. (a) reconstructed cross section of the distal shaft with landmarks (black dots) and semilandmarks (smaller red dots) on the elbow region. (b) Procrustes distances from the DNH 32 specimen to each of the fossil comparative specimens (with a lower value indicating a closer match)—filled symbols indicate fossils identified from a taxon-specific temporal/geographic context and numbers correspond to those in Supporting Information Table 1; and (c) plot of the first three principal components (PCs) for the geometric morphometric analysis of the elbow region. “Australopithecus (southern)” includes A. africanus and A. sediba specimens; “Australopithecus (eastern) includes A. anamensis and A. afarensis specimens. Paranthropus boisei specimens were included in the calculation of the principal component axes, but are not plotted for visual clarity of the figure. The convex hull associated with the purported P. boisei specimens falls with the other fossils along PC1 and overlaps that of Australopithecus (eastern) but no other fossil groups.
Cover art for A Tribe Called Quest's "The Low End Theory."
The OH 5 cranium originally attributed to Zinjanthropus boisei (Leakey, 1959) but now referred to as Paranthropus boisei. Photo credit: https://humanorigins.si.edu/evidence/human-fossils/fossils/oh-5
The fifth metacarpal and hamate of (from left to right): Paranthropus boisei, Gorilla beringei, Pan troglodytes, Australopithecus afarensis, and a recent Homo sapiens. Paranthropus boisei shares with gorillas a hyper-robust fifth metacarpal and hamulus of the hamate.
The hand of Paranthropus boisei (fossil specimen KNM-ER 101000).
Figure 19 from Pickford et al. OCO BAR 900’11, hominid mandible fragments from Sinibo, Tugen Hills, Kenya, prior to cleaning.
Figure 1 from Robbins et al. Arboreal gorillas (A) Juvenile (indicated in the canopy in purple) and silverback (indicated climbing on lower branch in yellow) Loango western gorillas. (B) Silverback Loango western gorilla. (C) Adult female and infant Bwindi mountain gorillas. (D) Silverback Bwindi mountain gorilla. Photo credits: Martha M. Robbins/MPI-EVA.
Figure 1 from Berg et al (2025): Three-dimensional polygon models derived from surface scanning of DNH 43. A) sacrum (DNH 43A) with arrow indicating cranially-directed deformation of the left side of the sacral plateau; B) bisection and reflection of the relatively undistorted right side to reconstruct the left side; C) medial view of the two refit pieces of the os coxae (DNH 43B); D) anterior view of the articulated pelvis with the reconstructed sacrum and the right os coxae reflected to reproduce the left side; E) superior view of the articulated pelvis; F) lateral view of the articulated pelvis.
From Berg et al Supplementary figure 3: Pelvic incidence (56°) measured in the partially reconstructed and articulated DNH 43. The pelvis has been bisected sagitally for demonstration. The angle was measured following the 3D method from Peleg et al. Landmarks A and B represent the anterior- and posterior-most points on the sacral plateau’s sagittal midline. Landmark C represents the midpoint of a line segment that connects the centres of the right and left acetabular fossae. The pelvic incidence angle (red arrow) was then calculated as the angle between the orthogonal to line segment AB (which approximates the orientation of the sacrum) and line segment AC. The blue boxes represent an approximate reconstruction of the inferred positioning of the caudal three lumbar vertebrae in lordosis.
Figure 9. Articulation of the SWT1/HR-2b hominin femur (top) and SWT1/HR-2c hominin tibia (bottom) in anterior view (superior up).
Paleoanthropologist Caley Orr with the original Taung Child specimen of Australopithecus africanus housed at Wits University in Johannesburg, South Africa. He is gesticulating in disappointment that there are no associated hand bones. I mean, why even bother?
Image from Skinner et al (2025) showing the SK 46 fossil specimen (a cranium typically attributed to Paranthropus robustus) from Swartkrans, South Africa. The specimen is depicted in sagittal section from the microCT image (top right) and as surface renderings of the cranium in anterior view (top left), lateral view (bottom left), and inferior view (bottom right).
Music Not Allowed in the Anatomy Lab: 1. Nickelback. 2. Staind 3. Borgore 4. Bro-Country Music 5. Coldplay 6. Smashmouth 7. Incubus 8. No overly vulgar language or subject matter (unless the Dean is confirmed to be off campus) 9. Nickelback 10. Uptown Funk (limited to one play per semester) 11. Maroon 5 12. Blink-182 13. Never Gonna Give You Up by Rick Astley (limited to one Rick Roll per semester) 14. Kanye/Ye/Yeezus 15. Creed 16. The Friends theme song 17. Any remix of "Who Let the Dogs Out?"
Figure 6 from Green et al (2010; A draft sequence of the Neandertal genome. Science 328: 710-722) Four possible scenarios of genetic mixture involving Neandertals. Scenario 1 represents gene flow into Neandertal from other archaic hominins, here collectively referred to as Homo erectus. This would manifest itself as segments of the Neandertal genome with unexpectedly high divergence from present-day humans. Scenario 2 represents gene flow between late Neandertals and early modern humans in Europe and/or western Asia. We see no evidence of this because Neandertals are equally distantly related to all non-Africans. However, such gene flow may have taken place without leaving traces in the present-day gene pool. Scenario 3 represents gene flow between Neandertals and the ancestors of all non-Africans. This is the most parsimonious explanation of our observation. Although we detect gene flow only from Neandertals into modern humans, gene flow in the reverse direction may also have occurred. Scenario 4 represents old substructure in Africa that persisted from the origin of Neandertals until the ancestors of non-Africans left Africa. This scenario is also compatible with the current data.
2001 Institute of Human Origins team gathered at the site of discovery of the Lucy specimen.
Homo erectus Skull 5 from the 1.8 million year old site of Dmanisi (Republic of Georgia) wearing a Santa hat.
Defiant chimpanzee fist!