Stephen R Frost

University of Oregon | UO

The middle Pliocene site of Woranso-Mille in the Afar Region of Ethiopia has yielded numerous significant early hominin fossils representing multiple, coexisting taxa. Here we report on another significant discovery, the oldest partial skeleton of the papionin, Theropithecus. The specimen was recovered from the Aralee Issie collection area over mul...

Despite recent advances in chronometric techniques (e.g., Uranium-Lead [U-Pb], cosmogenic nuclides, electron spin resonance spectroscopy [ESR]), considerable uncertainty remains regarding the age of many Plio-Pleistocene hominin sites, including several in South Africa. Consequently, biochronology remains important in assessments of Plio-Pleistocen...

Humans evolved in the dynamic landscapes of Africa under conditions of pronounced climatic, geological and environmental change during the past 7 million years. This book brings together detailed records of the paleontological and archaeological sites in Africa that provide the basic evidence for understanding the environments in which we evolved....

Objectives Geographic variation is an important feature among primates, but the mechanisms underlying it are not well understood. Macaques are geographically widespread and have been translocated to captive populations, providing a prime opportunity to evaluate changes in cranial form in response to a novel environment. Clinal variation was assesse...

The Colobines are a group of Afroeurasian monkeys that exhibit extraordinary behavioural and ecological diversity. With long tails and diverse colourations, they are medium-sized primates, mostly arboreal, that are found in many different habitats, from rain forests and mountain forests to mangroves and savannah. Over the last two decades, our unde...

Old World monkeys, or cercopithecoids, are a diverse and widespread group of primates found throughout Africa and Asia. They are characterised by their specialised molar teeth, quadrupedal posture and locomotor behaviour, often spending more time on the ground than other primates, as well as their frequently large and complex social groups. They su...

In studies of ontogenetic allometry, ontogenetic scaling has often been invoked to explain cranial morphological differences between smaller and larger forms of closely related taxa. These scaled variants in shape have been hypothesized to be the result of the extension or truncation of common growth allometries. In this scenario, change in size is...

Many authors have hypothesized an association between rates of morphological evolution and rates of species diversification, however, this association has yet to be empirically tested in the primate cranium. In this investigation, we used phylogeny-based approaches to examine the relationship between rates of species diversification, rates of crani...

The adoption of bipedalism is a key benchmark in human evolution that has impacted talar morphology. Here, we investigate talar morphological variability in extinct and extant hominins using a 3D geometric morphometric approach. The evolutionary timing and appearance of modern human–like features and their contributions to bipedal locomotion were e...

Recent fieldwork at Kanapoi has expanded the sample of fossil cercopithecids, facilitating a re-appraisal of their taxonomy. The assemblage now includes at least one species of cercopithecin, two papionins, and two colobines. The guenon Nanopithecus browni is similar in dental size to extant Miopithecus. We tentatively re-affirm the identification...

Objectives: The primate talus is known to have a shape that varies according to differences in locomotion and substrate use. While the modern human talus is morphologically specialized for bipedal walking, relatively little is known on how its morphology varies in relation to cultural and environmental differences across time. Here we compare tali...

Previous investigations of the primate talo‐crural joint (TCJ; specifically on the talus and distal tibia) have demonstrated that substrate preference significantly influences morphology, but this association is not necessarily found in subadults. This has been interpreted as the result of a plastic, behaviorally induced response of bone due to sub...

While the analysis of ontogenetic trajectories is common in geometric morphometrics (GM), the simultaneous comparison of several trajectories can be unwieldy and is, in some cases, unable to make use of one of the main advantages of GM, visualization. Furthermore, due to the paucity of the paleontological record, analyses of trajectories are often...

Objectives Prior examination of the ontogeny of Hominoid talo‐crural joint morphology using Singular Warp analysis suggested both a genetic and epigenetic signal during development. This question is examined using trajectory analysis and its implications for the Hominin fossil record explored. Materials and methods Trajectory analysis was used to...

Baboons (Papio hamadryas) are among the most successful extant primates, with a minimum of six distinctive forms throughout Sub-Saharan Africa. However, their presence in the fossil record is unclear. Three early fossil taxa are generally recognized, all from South Africa: Papio izodi, Papio robinsoni and Papio angusticeps. Because of their derived...

Objectives: The smallest extant member of genus Papio, the Kinda baboon exhibits low sexual dimorphism and a distinctive cranial shape. Ontogenetic scaling accounts for most cranial-shape differences within Papio, but studies have shown that the Kinda follows a separate ontogenetic trajectory. If so, its cranial-dimorphism pattern should differ fro...

This poster presents some pilot analyses from my doctoral dissertation.

The Pleistocene hominin site of Makuyuni, near Lake Manyara, Tanzania, is known for fossils attributable to Homo and Acheulean artifacts (Ring et al., 2005; Kaiser et al., 2010; Frost et al., 2012). Here we describe the fossil primate material from the Manyara Beds, which includes the first nearly complete female cranium of Theropithecus oswaldi le...

Our results demonstrate that human shape tali are influenced by loading difference, presumably due to a combination of substrate used, lifestyles (nomadic vs. sedentary) and subsistence, resulting in different arthrokinematics in relation to how body weight is borne on the talus over the course of stance phase.

Since their origin in Africa during the Miocene epoch, Old World monkeys have spread throughout that continent and several different groups of them have also dispersed across Eurasia to become the most widespread and speciose family of nonhuman primates, even reaching locations well outside of the tropical rainforest habitats typical of other prima...

Climatic change has played an important role in primate evolution for at least the last 66 million years. It has been an important driver in biogeography and the expanding and contracting ranges of different primate radiations, as well as in the abundance and diversity of primates in different ecosystems. It has been important in driving speciation...

Pleistocene primates are broadly similar to living forms and fossils have been found in Africa, Asia, Europe, Madagascar, the Greater Antilles, and South America. Nonetheless, most species known from the Pleistocene are extinct, as are the majority of genera. While many species are similar in size to living forms, most are larger, with the largest...

Recent morphometric research has generated opposing conclusions regarding the ontogenetic trajectories of catarrhine crania, possibly due to the ontogenetic proxies used to calculate them. Therefore, we used three surrogates: size, molar eruption, and chronological age to generate trajectories in a known-age sample to produce ontogenetic trajectori...

Fossil monkeys have long been used as important faunal elements in studies of African Plio-Pleistocene biochronology, particularly in the case of the South African karst cave sites. Cercopithecoid fossils have been known from Tanzania's Olduvai Gorge for nearly a century, with multiple taxa documented including Theropithecus oswaldi and Cercopithec...

This study investigates the taxonomic and morphometric affinities of a newly catalogued fossil papionin from Kromdraai A. The juvenile specimen (KA 5993), which preserves the face and cranial base anterior to the spheno-occipital synchondrosis, is notable for its small size and well-developed maxillary fossae. Geometric morphometric analyses were c...

The langurs (subfamily: Colobinae) of Southeast Asia have undergone many phylogenetic revisions. Incongruent results from recent genetic work suggest Trachypithecus pileatus and Trachypithecus geei are the result of ancient hybridization between Semnopithecus and Trachypithecus species. Geographically, these species are located between the distribu...

Bergmann’s rule predicts that body size increases with distance from the equator. This pattern has been noted in wild macaque populations, but captive populations relocated to new latitudes have not been examined for this pattern. They are therefore a prime population for analyzing whether Bergmann’s rule is influenced more by natural selection or...

The incorporation of C4 resources into hominin diet signifies increased dietary breadth within hominins and divergence from the dietary patterns of other great apes. Morphological evidence indicates that hominin diet became increasingly diverse by 4.2 million years ago but may not have included large proportions of C4 foods until 800 thousand years...

Understanding talar functional morphology is pivotal to understand the evolution of hominin bipedalism due to its role during locomotion, in part controlling dorsi-plantar flexion, ab-adduction and in-eversion of the foot. Despite recent contributions having utilized increasingly advanced digital methods, further work is warranted to quantify talar...

The number of recognized Macaca species on the Indonesian island of Sulawesi has varied depending on the methods used. This study applies landmark-based geometric morphometrics and various multivariate analyses to reassess the diversity of macaques on the island. Forty-five three-dimensional landmarks were recorded using a Microscribe 3D-X on 398...

Fluctuating Asymmetry (FA) is related to testosterone levels and mating strategies; typically males are more asymmetrical than females. Second-to-fourth digit ratio (2D:4D) is correlated with developmental testosterone levels. Using 2D:4D and cranial FA from 19 primates, we compare the relationship between these variables to their respective mating...

Thumb reduction is among the most important features distinguishing the African and Asian colobines from each other and from other Old World monkeys. In this study we demonstrate that the partial skeleton KNM-ER 4420 from Koobi Fora, Kenya, dated to 1.9 Ma and assigned to the Plio-Pleistocene colobine species Cercopithecoides williamsi, shows marke...

Recent geometric morphometric studies have used different approaches for assessing cranial ontogeny in primates. We aim to determine 1) how different are ontogenetic trajectories produced with different ontogenetic surrogates? and 2) which ontogenetic surrogate most accurately tracks ontogenetic shape change in the cranium? Forty three 3D landmarks...

The fossil colobine genus Cercopithecoides is temporally, geographically, and morphologically diverse. There are currently six species recognized from Late Miocene to Pleistocene sites in Africa with a possible seventh form present at Kromdraai B and Swartkrans in South Africa, for which the name C. coronatus (Freedman, 1957) is available. We focus...

The hominin fossil record is punctuated by variation and rapid change in talo-crural articular joint shape. Prior studies in a diverse Catarrhine sample using Singular Warp analysis has revealed that similar shape is observed across superfamilies due to substrate use, but genera can differ in shape in response to the same behavioral stimulus. Ontog...

Diagenetic distortion can be a major obstacle to collecting quantitative shape data on paleontological specimens, especially for three-dimensional geometric morphometric analysis. Here we utilize the recently -published algorithmic symmetrization method of fossil reconstruction and compare it to the more traditional reflection & averaging approach....

The upper ankle joint forms a single articular plane between organism and the foot and substrate. Singular warp analysis shows that its shape reflects substrate use. This study explores whether the differences in shape are genetic with a developmental trajectory evident during ontogeny or epigenetic and the result of substrate use by the individual...

This investigation analyzes cranial shape evolution over more than 3 million years of Theropithecus oswaldi evolutionary history. A single, anagenetically evolving lineage that shows marked increase in size and adaptation to grazing through time, T. oswaldi is recognized as three successive chrono-subspecies: T. o. darti, T. o. oswaldi, and T. o. l...

Significance Mammalian extinction during the past several hundred thousand years has been a major focus for evolutionary biologists, geologists, and archaeologists, often being linked to climate change and human overhunting. Until relatively recently, study has been largely restricted to the Americas, Europe, and Australasia. We present the oldest...

The appositional articular morphology of the talo-crural joint is the third component of the joint complex. It is a site of internal integration of this highly stable functional evolutionary unit. Prior studies of the other two components, tibia and talus, demonstrated that substrate preference influenced their articular shape. This effect was unre...

The tar pits of Rancho La Brea are a unique window onto the biology and ecology of the terminal Pleistocene in southern California. In this study we capitalize on recent advances in understanding of La Brea tar pit chronology to perform the first morphometric study of crania of the dire wolf, Canis dirus, over time. We first present new data on too...

The taxonomy of the fossil colobine genus Cercopithecoides has been debated by paleoprimatologists for decades. Currently, six species of Cercopithecoides are recognized in the Late Miocene to Plio-Pleistocene of South and East Africa. C. williamsi, found at Koobi Fora, Leba, Makapansgat, Sterkfontein, Swartkrans, Bolt’s Farm, and Kromdraai, is one...

The distal component of the talo-crural joint, the talus, was compared, using geometric morphometrics, in 219 specimens from nine extant taxa to identify differences in shape and the factors influencing them. The specimens were laser scanned, digitally reconstructed, and landmarked. The whole talus, proximal and distal articular facet subgroups wer...

Taxonomy of the South African fossil colobine Cercopithecoides williamsi has been debated by paleoprimatologists for decades. It has been suggested that the cranial morphology of specimens from Makapansgat (MP), Sterkfontein (STS/W), and Bolt's Farm (BF) shows more variation than expected for a single species. Thirty-seven three-dimensional landmar...

Is plasticity in joint shape observed with different substrate use? The current study examines the appositional articular morphology (AAM) of the talo‐crural joint across catarrhine primates. Matched tibiae and tali from 245 adults and 163 subadults from 6 hominoid and 6 cercopithecoid taxa ( H. sapiens, G. gorilla, P. troglodytes, P. paniscus, Pon...

Three fossils, a cranium of Papio, a cercopithecid frontal bone, and a mandible of juvenile Papio, have been recovered from cave deposits in the !Ncumtsa (Koanaka) Hills of western Ngamiland, Botswana. These specimens are significant because well-preserved crania of Papio are extremely rare in the fossil record outside of South Africa and because t...

The number of Sulawesi macaque species recognized by different authorities varies from one to seven. Previous studies have looked at hybrid zones, ecological variation, coloration, and behavior; to determine the number of possible species. This study uses landmark-based geometric morphometrics and various multivariate analyses to examine this quest...

The Manyara Beds in the area of Makuyuni Village in the Lake Manyara Basin, Tanzania have been studied for nearly a century, but interpretations of their age have ranged from Middle Pleistocene to Late Pliocene. New geological, paleontological and archeological fieldwork was conducted at the site and has provided siginificant new evidence, includin...

The ∼25 m-thick Manyara Beds section near Makuyuni, northern Tanzania, contain abundant Acheulean lithics and vertebrate fossils, including possible Homo erectus remains. However, the age of the unit (and its most productive fossil and archaeological localities) has been provisional. To address this we measured 20 new stratigraphic sections and col...

Old World monkeys, or cercopithecoids, are a diverse and widespread group of primates found throughout Africa and Asia. They are characterised by their specialised molar teeth, quadrupedal running behaviour, often spending more time on the ground than other primates, as well as their often large and complex social groups. They survive in the widest...

This article uses data on the dental eruption pattern and life history of Tarsius to test the utility of Schultz's rule. Schultz's rule claims a relationship between the relative pattern of eruption and the absolute pace of dental development and life history and may be useful in reconstructing life histories in extinct primates. Here, we document...

The proximal component of the talo-crural joint, the tibia, was compared, using geometric morphometrics, in 240 specimens from 10 extant taxa to identify differences in shape and the factors influencing them. The specimens were laser scanned, digitally reconstructed, and landmarked. Regression analysis was used to evaluate tibial shape, and signifi...

Old World monkeys are some of the most common and visible components of the modern mammalian fauna of Africa, and are the dominant nonhuman primates in Africa today with respect to the overall numbers of species present and the number of ecological zones inhabited. What is rarely appreciated is that Old World monkeys have risen to a position of eco...

This volume is a comprehensive review of the African mammalian fossil record over the past 65 million years. The book includes current taxonomic and systematic revisions of all African mammal taxa, detailed compilations of fossil site occurrences, and a wealth of information regarding paleobiology, phylogeny, and biogeography. Primates, including h...

Rungwecebus kipunji is a recently discovered, critically endangered primate endemic to southern Tanzania. Although phenetically similar to mangabeys, molecular analyses suggest it is more closely related to Papio or possibly descended from an ancient population of baboon-mangabey hybrids. At present, only a single kipunji specimen, an M1-stage juve...

During several transgression and regression cycles the Pleistocene Lake Manyara (North Tanzania) deposited a lacustrine sequence which is exposed to the south, north and east of the present lake. The lower member of the Makuyuni Beds is best exposed south of the town of Makuyuni where it yielded both a rich mammal fauna and Palaeolithic stone artef...

Rungwecebus kipunji is a recently discovered, critically endangered primate endemic to southern Tanzania. Although phenetically similar to mangabeys, molecular analyses suggest it is more closely related to Papio or possibly descended from an ancient population of baboon-mangabey hybrids. At present, only a single kipunji specimen, an M1-stage juve...

A diverse assemblage of large mammals is spatially and stratigraphically associated with Ardipithecus ramidus at Aramis. The most common species are tragelaphine antelope and colobine monkeys. Analyses of their postcranial remains situate them in a closed habitat. Assessment of dental mesowear, microwear, and stable isotopes from these and a wider...

The Middle Awash Research Project has collected a large sample of fossil cercopithecids from the Aramis, Kuseralee, and Sagantole drainages in the Middle Awash paleoanthropological study area of Ethiopia. These sites have been securely dated to 4.4 Ma. The craniodental material from this assemblage supports the diagnoses of two distinct new genera...

Localized Components Analysis (LoCA) is a new method for describing surface shape variation in an ensemble of objects using a linear subspace of spatially localized shape components. In contrast to earlier methods, LoCA optimizes explicitly for localized components and allows a flexible trade-off between localized and concise representations, and t...

This study conducts a phylogenetic analysis of extant African papionin craniodental morphology, including both quantitative and qualitative characters. We use two different methods to control for allometry: the previously described narrow allometric coding method, and the general allometric coding method, introduced herein. The results of this stud...

There are a total of 16 fossil cercopithecid specimens, representing at least 10 individuals, from the Chiwondo Beds of northern Malawi. The majority of this material is derived from the Middle Pliocene Unit 3A, but one specimen is from the Early Pliocene Unit 2. This latter specimen is from a papionin of indeterminate genus similar in size to Para...

Fred Szalay is a polymath of evolutionary morphology. From the mid-1960s (Szalay, 1968) to at least the mid-1980s (Szalay et al., 1987), he was acknowledged as the leading researcher on non-anthropoid fossil primates, complementing the anthropoid expertise of Elwyn Simons who had just laid the foundations for paleoprimatology as a distinct field th...

Ardipithecus fossils found in late Miocene and early Pliocene deposits in the Afar region of Ethiopia, along with Sahelanthropus tchadensis from Chad and Orrorin tugenensis from Kenya, are among the earliest known human ancestors and are considered to be the predecessors to the subsequent australopithecines (Australopithecus anamensis and Australop...