Papers by Craig Wuthrich
Scientific Reports, 2019
Considerable taxonomic diversity has been recognised among early Miocene catarrhines (apes, Old W... more Considerable taxonomic diversity has been recognised among early Miocene catarrhines (apes, Old World monkeys, and their extinct relatives). However, locomotor diversity within this group has eluded characterization, bolstering a narrative that nearly all early catarrhines shared a primitive locomotor repertoire resembling that of the well-described arboreal quadruped Ekembo heseloni. Here we describe and analyse seven catarrhine capitates from the Tinderet Miocene sequence of Kenya, dated to ~20 Ma. 3D morphometrics derived from these specimens and a sample of extant and fossil capitates are subjected to a series of multivariate comparisons, with results suggesting a variety of locomotor repertoires were present in this early Miocene setting. One of the fossil specimens is uniquely derived among early and middle Miocene capitates, representing the earliest known instance of great ape-like wrist morphology and supporting the presence of a behaviourally advanced ape at Songhor. We suggest Rangwapithecus as this catarrhine’s identity, and posit expression of derived, ape-like features as a criterion for distinguishing this taxon from Proconsul africanus. We also introduce a procedure for quantitative estimation of locomotor diversity and find the Tinderet sample to equal or exceed large extant catarrhine groups in this metric, demonstrating greater functional diversity among early catarrhines than previously recognised.
Nature Education Knowledge, 2015
Living hominoids (apes) are united by features related to their unusual locomotion, but few such ... more Living hominoids (apes) are united by features related to their unusual locomotion, but few such traits are found in the earliest fossil forms. Which adaptations were likely present in the earliest hominoids? Fossil teeth. The fossilized palate of UMP 6211 Morotopithecus bishopI, occlusal view. Like other Miocene hominoids, the canines are robust, as visible form the large crown base on the left side.
Conference presentations by Craig Wuthrich
American Journal of Physical Anthropology, 2019
The anatomy of the wrist has been instrumental
in reconstructing the positional behavior of many
... more The anatomy of the wrist has been instrumental
in reconstructing the positional behavior of many
extinct primates, but very few carpal traits have
been quantitatively confirmed to consistently
covary with specific locomotor modes or postures
among extant species. In this study, shape traits
predicted to facilitate specific positional behaviors
were quantified in a broad anthropoid sample
using μCT and laser scan data and evaluated
for covariance with both quantitative and categorical
characterizations of positional behavior.
Traits found to covary with hypothetically linked
behavior(s) while accounting for allometry and
phylogeny were then used to create multivariate
models evaluating the efficacy of carpal
morphology in estimating anthropoid behavioral
repertoires.
Carpal morphology is found to strongly covary
with positional behavior across the anthropoid
clade. Multivariate classification accuracy of
wrist posture exceeds 90% after repeated 10-fold
cross-validation, and proportions of suspension,
quadrupedalism, climbing, and arboreality are
accurately estimated from carpal morphology
of out-of-sample extant taxa. Covariance is
greatest with suspensory behavior, with the
carpus modified to increase mobility at the
midcarpal and proximal carpal joints, enhance
flexor carpi ulnaris leverage and transmission
of associated forces, and stabilize the capitohamate
joint against non-stereotypical force
vectors. Covariance with arboreal-only locomotor
proportions is greater than with total proportions,
reflecting the need for safe and secure grasping
even among the most terrestrial anthropoids.
These results advance our understanding of the
complex relationships among form, function, and
phylogeny while guiding future behavioral reconstructions
of fossil carpal specimens.
American Journal of Physical Anthropology, 2018
Digitigrade hand postures are thought to have evolved independently in several lineages of extant... more Digitigrade hand postures are thought to have evolved independently in several lineages of extant, highly terrestrial cercopithecines. The ability to diagnose this hand posture in cercopithecoid fossil remains would be useful in understanding the clade’s locomotor history, but features distinguishing digitigrady have been difficult to identify. Here we present analysis of metrics derived from 3D carpal models of 336 individuals from 28 anthropoid taxa. Models evaluating morphological covariance with digitigrady incorporate phylogeny and body size. Traits distinguishing digitigrade taxa from other anthropoids were found to contribute to discrete functional complexes within the carpus, including a distal mortise enhancing carpometacarpal joint stability and a narrow central column reflecting predominantly parasagittal limb movement during habitual locomotion, with additional features facilitating load transmission and stability at the midcarpal and antebrachiocarpal joints. Traits with statistical and plausible biomechanical links to digitigrady were used to construct a multivariate classifier, with accuracy exceeding 90% after repeated 10-fold cross-validation. When applied to a small fossil cercopithecoid sample, Victoriapithecus macinnesi is classified with high probability as palmigrade, consistent with previous reconstructions finding it to have maintained substantial reliance on arboreal substrates. Theropithecus brumpti demonstrates comparatively greater affinity with digitigrade cercopithecines; its capitate has a larger dorsal nonarticular region and more concave hamate facet, the distal facets of the capitate and lunate are narrower, and its stylo-triquetral articulation is larger. In other diagnostic features the fossil taxa do not differ, however. T. brumpti is classified as digitigrade with a low posterior probability, perhaps indicating incipiency of its terrestrial adaptations.
American Journal of Physical Anthropology, 2018
Several features of the great ape carpus have been hypothesized to relate to loading of the wrist... more Several features of the great ape carpus have been hypothesized to relate to loading of the wrist during ulnar deviation, which is primarily thought to occur during vertical climbing and suspension. This study investigates the presence of some of these features among great apes, and examines the role of wrist adduction during different positional behaviors in chimpanzees. Video footage of ad libitum positional behavior was collected of Ngogo chimpanzees in Kibale Forest, Uganda. Frame-by-frame analysis was performed in iMovie, with wrist adduction angles extracted in ImageJ based on the axes of the forearm and the third metacarpal/third proximal phalanx, with the metacarpus parallel to the camera. Maximal ulnar deviation occurred during vertical climbing, but adduction also habitually occurred during knuckle-walking, vertical descent, as well as suspension. Analysis of three-dimensional shape variables extracted from 336 anthropoid carpals reveal great ape lunates to have reduced scaphoid facets and expanded radial facets, their triquetra to have enlarged lunate facets, and their capitates to have minimal contact with the fourth metacarpal. Each of these traits is plausibly associated with transmission of forces generated during adduction, as observed in chimpanzees, but future research is necessary to evaluate whether adduction during loading is consistent across great ape taxa for each behavioral mode. This study highlights the importance of testing hypothesized morpho-functional links by combining multiple lines of evidence from extant primates, in order to improve the reliability of functional inference from fossil morphology.
American Journal of Physical Anthropology, 2016
Songhor is one of a group of sites located around the lower slopes of the Miocene Volcano at Tind... more Songhor is one of a group of sites located around the lower slopes of the Miocene Volcano at Tinderet in western Kenya and has produced a diverse assemblage of primate fossils dated to ~19-20 Ma. Here we provide qualitative descriptions and comparative computational analysis (PCA and CVA) of several non-cercopithecoid catarrhine capitates recovered from Songhor between 1966 and 1996. These and several other Miocene catarrhine capitates were analyzed in association with a taxonomically diverse sample of extant anthropoids (n=374). Morphometric variables were extracted from 3D models derived from laser surface and micro-CT scans. The results indicate that KNM-SO 31245 and 31246 are morphologically similar to each other and to KNM-CA 409 from nearby Koru, as well as to specimens of Proconsul (sensu lato) from Rusinga. They cluster together with a range of extant cercopithecoids, consistent with previous analyses of Rusinga material, suggesting the Tinderet specimens likely belong to Proconsul africanus. KNM-SO 1002 is similar in size to the above specimens, but is morphologically distinct, clustering with extant great apes and sharing several features with them, including mediolateral expansion of the head and body and a markedly waisted neck. This distinctive morphology suggests it belongs to a different taxon, with Rangwapithecus gordoni being the only other similarly-sized catarrhine known from Songhor. KNM-SO 1000 and 1001 resemble hylobatids and arboreal cercopithecoids, and their size is most similar to Trachypithecus cristatus of the extant sample. These factors are consistent with previous behavioral and body size reconstructions of postcrania attributed to Dendropithecus macinnesi.
Support was provided by the Leakey Foundation, the Boise Fund, and the Fulbright Program.
Syllabi by Craig Wuthrich
The goal of this class is to introduce students to some basic principles of functional musculoske... more The goal of this class is to introduce students to some basic principles of functional musculoskeletal anatomy in an evolutionary context. Students will learn the names of many of the bones and muscles in the human body, and will gain a basic understanding of how bone morphology varies in different animals with different behavioral repertoires. Over the course of the semester, the major functional morphological complexes will be discussed in turn, with an emphasis on important functional features and how human bones differ from those of extant and fossil nonhuman primates. We will discuss the major behavioral transitions within our evolutionary lineage, from pronogrady, to orthogrady, to bipedal standing, walking, and running, and finally to manipulative behaviors including throwing and tool use. Each lecture will also include discussion of common injuries or evolutionary " defects " , examples of extreme human performance, the types of morphological variation sometimes associated with exceptional ability, and some practical benefits of understanding evolutionary anatomy. Students will be asked to examine anatomical specimens to see first-hand how modern humans differ anatomically from our closest relatives, both living and extinct, and to understand how our anatomy facilitates or limits our physical abilities. No understanding of evolutionary theory or human anatomy will be assumed, but those without such knowledge will need to take special care to keep up with the readings and to seek additional assistance.
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Papers by Craig Wuthrich
Conference presentations by Craig Wuthrich
in reconstructing the positional behavior of many
extinct primates, but very few carpal traits have
been quantitatively confirmed to consistently
covary with specific locomotor modes or postures
among extant species. In this study, shape traits
predicted to facilitate specific positional behaviors
were quantified in a broad anthropoid sample
using μCT and laser scan data and evaluated
for covariance with both quantitative and categorical
characterizations of positional behavior.
Traits found to covary with hypothetically linked
behavior(s) while accounting for allometry and
phylogeny were then used to create multivariate
models evaluating the efficacy of carpal
morphology in estimating anthropoid behavioral
repertoires.
Carpal morphology is found to strongly covary
with positional behavior across the anthropoid
clade. Multivariate classification accuracy of
wrist posture exceeds 90% after repeated 10-fold
cross-validation, and proportions of suspension,
quadrupedalism, climbing, and arboreality are
accurately estimated from carpal morphology
of out-of-sample extant taxa. Covariance is
greatest with suspensory behavior, with the
carpus modified to increase mobility at the
midcarpal and proximal carpal joints, enhance
flexor carpi ulnaris leverage and transmission
of associated forces, and stabilize the capitohamate
joint against non-stereotypical force
vectors. Covariance with arboreal-only locomotor
proportions is greater than with total proportions,
reflecting the need for safe and secure grasping
even among the most terrestrial anthropoids.
These results advance our understanding of the
complex relationships among form, function, and
phylogeny while guiding future behavioral reconstructions
of fossil carpal specimens.
Support was provided by the Leakey Foundation, the Boise Fund, and the Fulbright Program.
Syllabi by Craig Wuthrich
in reconstructing the positional behavior of many
extinct primates, but very few carpal traits have
been quantitatively confirmed to consistently
covary with specific locomotor modes or postures
among extant species. In this study, shape traits
predicted to facilitate specific positional behaviors
were quantified in a broad anthropoid sample
using μCT and laser scan data and evaluated
for covariance with both quantitative and categorical
characterizations of positional behavior.
Traits found to covary with hypothetically linked
behavior(s) while accounting for allometry and
phylogeny were then used to create multivariate
models evaluating the efficacy of carpal
morphology in estimating anthropoid behavioral
repertoires.
Carpal morphology is found to strongly covary
with positional behavior across the anthropoid
clade. Multivariate classification accuracy of
wrist posture exceeds 90% after repeated 10-fold
cross-validation, and proportions of suspension,
quadrupedalism, climbing, and arboreality are
accurately estimated from carpal morphology
of out-of-sample extant taxa. Covariance is
greatest with suspensory behavior, with the
carpus modified to increase mobility at the
midcarpal and proximal carpal joints, enhance
flexor carpi ulnaris leverage and transmission
of associated forces, and stabilize the capitohamate
joint against non-stereotypical force
vectors. Covariance with arboreal-only locomotor
proportions is greater than with total proportions,
reflecting the need for safe and secure grasping
even among the most terrestrial anthropoids.
These results advance our understanding of the
complex relationships among form, function, and
phylogeny while guiding future behavioral reconstructions
of fossil carpal specimens.
Support was provided by the Leakey Foundation, the Boise Fund, and the Fulbright Program.