The pectoral girdle of StW 573 ('Little Foot') and its implications for shoulder evolution in the Hominina.

The ca. 3.67 Ma adult skeleton known as 'Little Foot' (StW 573), recovered from Sterkfontein Member 2 breccia in the Silberberg Grotto, is remarkable for its morphology and completeness. Preservation of clavicles and scapulae, including essentially complete right-side elements, offers opportunities to assess morphological and functional aspects of a nearly complete Australopithecus pectoral girdle. Here we describe the StW 573 pectoral girdle and offer quantitative comparisons to those of extant hominoids and selected homininans. The StW 573 pectoral girdle combines features intermediate between those of humans and other apes: a long and curved clavicle, suggesting a relatively dorsally positioned scapula; an enlarged and uniquely proportioned supraspinous fossa; a relatively cranially oriented glenoid fossa; and ape-like reinforcement of the axillary margin by a stout ventral bar. StW 573 scapulae are as follows: smaller than those of some homininans (i.e., KSD-VP-1/1 and KNM-ER 47000A), larger than others (i.e., A.L. 288-1, Sts 7, and MH2), and most similar in size to another australopith from Sterkfontein, StW 431. Moreover, StW 573 and StW 431 exhibit similar structural features along their axillary margins and inferior angles. As the StW 573 pectoral girdle (e.g., scapular configuration) has a greater affinity to that of apes-Gorilla in particular-rather than modern humans, we suggest that the StW 573 morphological pattern appears to reflect adaptations to arboreal behaviors, especially those with the hand positioned above the head, more than human-like manipulatory capabilities. When compared with less complete pectoral girdles from middle/late Miocene apes and that of the penecontemporaneous KSD-VP-1/1 (Australopithecus afarensis), and mindful of consensus views on the adaptiveness of arboreal positional behaviors soliciting abducted glenohumeral joints in early Pliocene taxa, we propose that the StW 573 pectoral girdle is a reasonable model for hypothesizing pectoral girdle configuration of the crown hominin last common ancestor.

Elevated activity levels do not influence extrinsic fiber attachment morphology on the surface of muscle-attachment sites.

Extrinsic fibers (EFs) are a type of penetrating collagenous fiber, closely related to the periodontal ligament, which help anchor soft tissue into bone. These fibers are associated with muscle attachment sites (entheses). Their size and grouping patterns are thought to be indicative of the loading history of the muscle. EFs are of particular significance in anthropology as potential tools for the reconstruction of behavior from skeletal remains and, specifically, entheses. In this study, we used a mouse model to experimentally test how activity level alters the morphology of EF insertion sites on the bone surface of a fibrocartilaginous enthesis, the biceps brachii insertion. Further, we adapted surface metrological techniques from studies of dental wear to perform automated, quantitative and non-destructive analysis of bone surface histology. Our results show that experimentally increased activity had no significant effect on the quantity or density of EF insertions at the enthesis, nor on the size of those insertions. Although EF presence does indicate muscle attachment, activity did not have an observable effect on EF morphology.

Predator-mediated effects of severe drought associated with poor reproductive success of a seabird in a cross-ecosystem cascade.

Despite the profound impacts of drought on terrestrial productivity in coastal arid ecosystems, only a few studies have addressed how drought can influence ecological cascades across ecosystem boundaries. In this study, we examine the consequences of rainfall pulses and drought that subsequently impact the breeding success of a threatened nocturnal seabird, the Scripps's Murrelet (Synthliboramphus scrippsi). On an island off the coast of southern California, the main cause of reduced nest success for one of their largest breeding colonies is egg predation by an endemic deer mouse (Peromyscus maniculatus elusus). Mice on the island have an opportunistic diet of primarily terrestrial sources, but drastic declines in terrestrial productivity from drought might be expected to increase their reliance on marine resources, including murrelet eggs. We compiled data on terrestrial and marine productivity between 1983 and 2013 to determine how conditions in these ecosystems influence murrelet nest success. We found that the severity of drought had the strongest negative impact on murrelet nest success. We calculated that the reduction in fecundity during drought years due to increased egg predation by mice was substantial enough to produce a declining population growth rate. Nest success was much higher under normal or high rainfall conditions, depending on whether oceanic conditions were favorable to murrelets. Therefore, the more frequent and severe drought that is projected for this region could lead to an increased risk of murrelet population decline on this island. Our study highlights the need for understanding how species interactions will change through the effects of increasing drought and altered rainfall regimes under global change.

Humeral anatomy of the KNM-ER 47000 upper limb skeleton from Ileret, Kenya: Implications for taxonomic identification.

KNM-ER 47000 is a fossil hominin upper limb skeleton from the Koobi Fora Formation, Kenya (FwJj14E, Area 1A) that includes portions of the scapula, humerus, ulna, and hand. Dated to ∼1.52 Ma, the skeleton could potentially belong to one of multiple hominin species that have been documented in the Turkana Basin during this time, including Homo habilis, Homo erectus, and Paranthropus boisei. Although the skeleton lacks associated craniodental material, the partial humerus (described here) preserves anatomical regions (i.e., distal diaphysis, elbow joint) that are informative for taxonomic identification among early Pleistocene hominins. In this study, we analyze distal diaphyseal morphology and the shape of the elbow region to determine whether KNM-ER 47000 can be confidently attributed to a particular species. The morphology of the KNM-ER 47000 humerus (designated KNM-ER 47000B) is compared to that of other early Pleistocene hominin fossil humeri via the application of multivariate ordination techniques to both two-dimensional landmark data (diaphysis) and scale-free linear shape data (elbow). Distance metrics reflecting shape dissimilarity between KNM-ER 47000B and other fossils (and species average shapes) are assessed in the context of intraspecific variation within modern hominid species (Homo sapiens, Pan troglodytes, Gorilla gorilla, Pongo pygmaeus). Our comparative analyses strongly support attribution of KNM-ER 47000 to P. boisei. Compared to four other partial skeletons that have (justifiably or not) been attributed to P. boisei, KNM-ER 47000 provides the most complete picture of upper limb anatomy in a single individual. The taxonomic identification of KNM-ER 47000 makes the skeleton an important resource for testing future hypotheses related to P. boisei upper limb function and the taxonomy of isolated early Pleistocene hominin remains.

Cross-sectional properties of the humeral diaphysis of Paranthropus boisei: Implications for upper limb function.

A ∼1.52 Ma adult upper limb skeleton of Paranthropus boisei (KNM-ER 47000) recovered from the Koobi Fora Formation, Kenya (FwJj14E, Area 1A) includes most of the distal half of a right humerus (designated KNM-ER 47000B). Natural transverse fractures through the diaphysis of KNM-ER 470000B provide unobstructed views of cortical bone at two sections typically used for analyzing cross-sectional properties of hominids (i.e., 35% and 50% of humerus length from the distal end). Here we assess cross-sectional properties of KNM-ER 47000B and two other P. boisei humeri (OH 80-10, KNM-ER 739). Cross-sectional properties for P. boisei associated with bending/torsional strength (section moduli) and relative cortical thickness (%CA; percent cortical area) are compared to those reported for nonhuman hominids, AL 288-1 (Australopithecus afarensis), and multiple species of fossil and modern Homo. Polar section moduli (Zp) are assessed relative to a mechanically relevant measure of body size (i.e., the product of mass [M] and humerus length [HL]). At both diaphyseal sections, P. boisei exhibits %CA that is high among extant hominids (both human and nonhuman) and similar to that observed among specimens of Pleistocene Homo. High values for Zp relative to size (M × HL) indicate that P. boisei had humeral bending strength greater than that of modern humans and Neanderthals and similar to that of great apes, A. afarensis, and Homo habilis. Such high humeral strength is consistent with other skeletal features of P. boisei (reviewed here) that suggest routine use of powerful upper limbs for arboreal climbing.

El Niño/Southern Oscillation-driven rainfall pulse amplifies predation by owls on seabirds via apparent competition with mice.

Most approaches for assessing species vulnerability to climate change have focused on direct impacts via abiotic changes rather than indirect impacts mediated by changes in species interactions. Changes in rainfall regimes may influence species interactions from the bottom-up by increasing primary productivity in arid environments, but subsequently lead to less predictable top-down effects. Our study demonstrates how the effects of an EL Niño/Southern Oscillation (ENSO)-driven rainfall pulse ricochets along a chain of interactions between marine and terrestrial food webs, leading to enhanced predation of a vulnerable marine predator on its island breeding grounds. On Santa Barbara Island, barn owls (Tyto alba) are the main predator of a nocturnal seabird, the Scripps's murrelet (Synthliboramphus scrippsi), as well as an endemic deer mouse. We followed the links between rainfall, normalized difference vegetation index and subsequent peaks in mouse and owl abundance. After the mouse population declined steeply, there was approximately 15-fold increase in the number of murrelets killed by owls. We also simulated these dynamics with a mathematical model and demonstrate that bottom-up resource pulses can lead to subsequent declines in alternative prey. Our study highlights the need for understanding how species interactions will change with shifting rainfall patterns through the effects of ENSO under global change.

Scapular anatomy of Paranthropus boisei from Ileret, Kenya.

KNM-ER 47000A is a new 1.52 Ma hominin scapular fossil belonging to an associated partial skeleton from the Koobi Fora Formation, Kenya (FwJj14E, Area 1A). This fossil effectively doubles the record of Early Pleistocene scapulae from East Africa, with KNM-WT 15000 (early African Homo erectus) preserving the only other known scapula to date. KNM-ER 47000A consists of a complete glenoid cavity preserving a portion of the scapular spine and neck, the proximal half of the acromion, and a majority of the axillary border. A sufficient amount of anatomy is preserved to compare KNM-ER 47000A with scapulae of several Australopithecus species, extinct Homo, and living hominoids. The glenohumeral joint of KNM-ER 47000A is more laterally oriented than those of great apes and Australopithecus, aligning it closely with KNM-WT 15000 and modern humans. While this morphology does not imply a strong commitment to arboreality, its scapular spine is obliquely oriented-as in gorillas and some Australopithecus fossils-particularly when compared to the more horizontal orientation seen in KNM-WT 15000 and modern humans. Such a spine orientation suggests a narrow yet long infraspinous region, a feature that has been attributed to suspensory taxa. Accordingly, the morphology of KNM-ER 47000A presents conflicting behavioral implications. Nonetheless, a multivariate consideration of the available scapular traits aligns KNM-ER 47000A and Australopithecus with great apes, whereas KNM-WT 15000 resembles modern humans. The scapular morphology of KNM-ER 47000A is unique among fossil and extant hominoids and its morphological differences from KNM-WT 15000 strengthen the attribution of KNM-ER 47000 to Paranthropus boisei as opposed to early Homo. As the first evidence of scapular morphology in P. boisei, KNM-ER 47000A provides important new information on variation in hominin shoulder and upper limb anatomy from this critical period of hominin evolutionary history.

The upper limb of Homo naledi.

The evolutionary transition from an ape-like to human-like upper extremity occurred in the context of a behavioral shift from an upper limb predominantly involved in locomotion to one adapted for manipulation. Selection for overarm throwing and endurance running is thought to have further shaped modern human shoulder girdle morphology and its position about the thorax. Homo naledi (Dinaledi Chamber, Rising Star Cave, Cradle of Humankind, South Africa) combines an australopith-like cranial capacity with dental characteristics akin to early Homo. Although the hand, foot, and lower limb display many derived morphologies, the upper limb retains many primitive traits. Here, we describe the H. naledi upper extremity (excluding the hand) in detail and in a comparative context to evaluate the diversity of clavicular, scapular, humeral, radial, and ulnar morphology among early hominins and later Homo. Homo naledi had a scapula with a markedly cranially-oriented glenoid, a humerus with extremely low torsion, and an australopith-like clavicle. These traits indicate that the H. naledi scapula was situated superiorly and laterally on the thorax. This shoulder girdle configuration is more similar to that of Australopithecus and distinct from that of modern humans, whose scapulae are positioned low and dorsally about the thorax. Although early Homo erectus maintains many primitive clavicular and humeral features, its derived scapular morphology suggests a loss of climbing adaptations. In contrast, the H. naledi upper limb is markedly primitive, retaining morphology conducive to climbing while lacking many of the derived features related to effective throwing or running purported to characterize other members of early Homo.

Hominin track assemblages from Okote Member deposits near Ileret, Kenya, and their implications for understanding fossil hominin paleobiology at 1.5 Ma.

Tracks can provide unique, direct records of behaviors of fossil organisms moving across their landscapes millions of years ago. While track discoveries have been rare in the human fossil record, over the last decade our team has uncovered multiple sediment surfaces within the Okote Member of the Koobi Fora Formation near Ileret, Kenya that contain large assemblages of ∼1.5 Ma fossil hominin tracks. Here, we provide detailed information on the context and nature of each of these discoveries, and we outline the specific data that are preserved on the Ileret hominin track surfaces. We analyze previously unpublished data to refine and expand upon earlier hypotheses regarding implications for hominin anatomy and social behavior. While each of the track surfaces discovered at Ileret preserves a different amount of data that must be handled in particular ways, general patterns are evident. Overall, the analyses presented here support earlier interpretations of the ∼1.5 Ma Ileret track assemblages, providing further evidence of large, human-like body sizes and possibly evidence of a group composition that could support the emergence of certain human-like patterns of social behavior. These data, used in concert with other forms of paleontological and archaeological evidence that are deposited on different temporal scales, offer unique windows through which we can broaden our understanding of the paleobiology of hominins living in East Africa at ∼1.5 Ma.

Wind conditions on migration influence the annual survival of a neotropical migrant, the western yellow-breasted chat (Icteria virens auricollis).

BACKGROUND: Long-distance migratory birds in North America have undergone precipitous declines over the past half-century. Although the trend is clear, for many migrating species underpinning the exact causes poses a challenge to conservation due to the numerous stressors that they encounter. Climate conditions during all phases of their annual cycle can have important consequences for their survival. Here, using 15 years of capture-recapture dataset, we determined the effects of various climate factors during the breeding, wintering, and migrating stages on the annual survival of a western yellow-breasted chat (Icteria virens auricollis) population breeding in southwestern Canada. RESULTS: El Niño effects over the entire annual cycle had little influence on the annual apparent survival of yellow-breasted chats. However, we found evidence that wind conditions during migration, specifically average westerly wind speed or the frequency of storm events, had significant adverse effects on adult annual apparent survival. In comparison, precipitation levels on wintering ground had little to no influence on adult annual apparent survival, whereas growing degree days on the breeding ground had moderate but positive effects. CONCLUSIONS: In the face of climate change and its predicted impacts on climate processes, understanding the influence of weather conditions on the survival of migrating birds can allow appropriate conservation strategies to be adopted for chats and other declining neotropical migrants.

An assessment of exposure and effects of persistent organic pollutants in an urban Cooper's hawk (Accipiter cooperii) population.

Among the stressors confronting urban wildlife, chemical contaminants pose a particular problem for high trophic feeding species. Previous data from fortuitous carcass collections revealed surprisingly high levels of persistent organic pollutants in raptor species, including the Cooper's hawk (Accipiter cooperii), from urbanized areas of southwestern British Columbia, Canada. Thus, in 2012 and 2013, we followed up on that finding by measuring POPs in blood samples from 21 adult and 15 nestling Cooper's hawks in Vancouver, a large urban area in southwestern Canada. Reproductive success and circulating thyroid hormones were measured to assess possible toxicological effects. Model comparisons showed concentrations of polychlorinated biphenyls (ΣPCBs) were positively influenced by the level of urbanization. Total thyroxin (TT4) was negatively associated with increases in ΣPCBs. Total triiodothyronine (TT3) was negatively associated with ΣPCBs and polybrominated diphenyl ethers (ΣPBDEs). The legacy insecticide, dieldrin, appeared to have some negative influence on reproductive success. There is some evidence of biochemical perturbation by PBDEs and lingering impact of legacy POPs which have not been used for at least 40 years, but overall Cooper's hawks have successfully populated this urban environment.

What's New in Dentine Bonding?: Universal Adhesives.

The ability to bond restorations to dentine successfully is central to minimally invasive restorative dentistry. While dentine-bonding agents have gone through a variety of 'generations', it is the purpose of this paper to describe the latest dentine-bonding agents, the Universal Bonding Agents. These materials may be considered 'Universal' insofar as they may be considered to be capable of being used for direct and indirect dentistry, as well as being suitable for use in whichever etching modality the clinician considers appropriate, namely self-etch, etch and rinse or selective enamel etch. Laboratory investigations and initial clinical studies hold the promise that Universal Bonding Agents are a forward step in the quest for the ultimate bond to tooth substance. Clinical relevance: New Universal Bonding Agents appear to present a promising advance in bonding to dentine.

Cascading effects of predation risk determine how marine predators become terrestrial prey on an oceanic island.

Apex predators can suppress the foraging activity of mesopredators, which may then result in cascading benefits for the prey of those mesopredators. We studied the interactions between a top predator, the Barn Owl (Tyto alba), and their primary prey, an island endemic deer mouse (Peromyscus maniculatus elusus), which in turn consumes the eggs of seabirds nesting on Santa Barbara Island in California. Scripps's Murrelets (Synthliboramphus scrippsi), a threatened nocturnal seabird, arrive annually to breed on this island, and whose first egg is particularly vulnerable to predation by mice. We took advantage of naturally occurring extreme variations in the density of mice and owls on the island over 3 years and predicted that (1) mouse foraging would decrease with increasing predation risk from owls and moonlight and (2) these decreases in foraging would reduce predation on murrelet eggs. We measured the giving up densities of mice with experimental foraging stations and found that mice were sensitive to predation risk and foraged less when owls were more abundant and less during the full moon compared to the new moon. We also monitored the fates of 151 murrelet eggs, and found that murrelet egg predation declined as owl abundance increased, and was lower during the full moon compared to the new moon. Moreover, high owl abundance suppressed egg predation even when mice were extremely abundant. We conclude that there is a behaviorally mediated cascade such that owls on the island had a positive indirect effect on murrelet egg survival. Our study adds to the wider recognition of the strength of risk effects to structure food webs, as well as highlighting the complex ways that marine and terrestrial food webs can intersect.

Scapular shape of extant hominoids and the African ape/modern human last common ancestor.

Newly discovered early hominin fossil scapulae have bolstered investigations of scapular shape, which have long been used to interpret behavioral variation among primates. However, unexpected similarities between Pongo and Homo - particularly in scapular spine orientation - have raised questions about the functional utility of scapular morphology and its phylogenetic context in the hominin lineage. Not surprisingly, significant disagreement surrounds disparate morphological reconstructions of the modern human/African ape last common ancestor (LCA). Our study utilizes geometric morphometric (GM) approaches - two employing homologous, anatomical landmarks and a "spine-free" alternative using 98 sliding semilandmarks along the boundary of the subscapular fossa. The landmark-based "wireframe" GM analysis principally sorted groups by spine orientation: Homo and Pongo were similar to one another with more transversely-oriented spines as compared to Hylobates and the African apes. In contrast, Homo and Gorilla clustered together in our semilandmark analysis with superoinferiorly broad blades. Pan scapulae were similar, but had more mediolaterally compressed blades and laterally-positioned superior angles. Hylobates was superoinferiorly narrow, yet obliquely expanded relative to the vertebral border. Pongo scapulae were unique among hominoids in being nearly as broad as they were long. Previously documented 'convergence' of Homo and Pongo scapulae appears to be principally driven by similarities in spine orientation, rather than overall blade shape. Therefore, we contend that it is more parsimonious to reconstruct the African ape/Homo LCA scapula as being Gorilla-like, especially in light of similar characterizations of certain fossil hominin scapulae. Accordingly, the evolution of Pan (highly oblique spine and laterally-situated superior angle) and Homo (transversely-oriented spine) scapular morphology would have involved relatively minor shifts from this ancestral condition. These results support the prevailing molecular phylogeny and provide further insight into the behavioral implications of scapular shape in the LCA and fossil hominins.

Locomotor activity influences muscle architecture and bone growth but not muscle attachment site morphology.

The ability to make behavioural inferences from skeletal remains is critical to understanding the lifestyles and activities of past human populations and extinct animals. Muscle attachment site (enthesis) morphology has long been assumed to reflect muscle strength and activity during life, but little experimental evidence exists to directly link activity patterns with muscle development and the morphology of their attachments to the skeleton. We used a mouse model to experimentally test how the level and type of activity influences forelimb muscle architecture of spinodeltoideus, acromiodeltoideus, and superficial pectoralis, bone growth rate and gross morphology of their insertion sites. Over an 11-week period, we collected data on activity levels in one control group and two experimental activity groups (running, climbing) of female wild-type mice. Our results show that both activity type and level increased bone growth rates influenced muscle architecture, including differences in potential muscular excursion (fibre length) and potential force production (physiological cross-sectional area). However, despite significant influences on muscle architecture and bone development, activity had no observable effect on enthesis morphology. These results suggest that the gross morphology of entheses is less reliable than internal bone structure for making inferences about an individual's past behaviour.

Reconciling the convergence of supraspinous fossa shape among hominoids in light of locomotor differences.

Differences in scapular morphology between modern humans and the African and lesser apes are associated with the distinct locomotor habits of these groups. However, several traits, particularly aspects of the supraspinous fossa, are convergent between Homo and Pongo-an unexpected result given their divergent locomotor habits. Many morphological assessments of the scapula rely on the limited number of static landmarks available, and traditional approaches like these tend to oversimplify scapular shape. Here, we present the results of two geometric morphometric (GM) analyses of hominoid supraspinous fossa shape-one employing five homologous landmarks and another with 83 sliding semilandmarks-alongside those of traditional methods to evaluate if three-dimensional considerations of fossa shape afford more comprehensive insights into scapular shape and functional morphology. Traditional measures aligned Pongo and Homo with narrow and transversely oriented supraspinous fossae, whereas African ape and Hylobates fossae are broader and more obliquely situated. However, our GM results highlight that much of the convergence between Homo and Pongo is reflective of their more medially positioned superior angles. These approaches offered a more complete assessment of supraspinous shape and revealed that the Homo fossa, with an intermediate superior angle position and moderate superoinferior expansion, is actually reminiscent of the African ape shape. Additionally, both Pongo and Hylobates were shown to have more compressed fossae, something that has not previously been identified through traditional analyses. Thus, the total morphological pattern of the Pongo supraspinous fossa is unique among hominoids, and possibly indicative of its distinctive locomotor habits.

Individual quality explains association between plumage colouration, arrival dates and mate acquisition in yellow warblers (Setophaga petechia).

BACKGROUND: In many bird species colour traits influence social dominance and breeding success. In our study we first evaluated whether the colour of the basic plumage (tail feathers grown at the end of the breeding season), that provides an index of individual quality, influenced winter habitat use by yellow warblers. We then evaluated whether winter habitat use (inferred using δ13C and δ15N signatures of winter grown greater-coverts) influenced alternate plumage colouration, after controlling for individual quality using basic plumage colouration. Finally, we investigated whether basic and alternate plumage colouration influenced arrival dates, mate acquisition, breeding phenology and reproductive success of yellow warblers breeding in southern (Revelstoke, B.C.) and arctic (Inuvik, N.W.T.) Canada. RESULTS: The colour (chroma and hue) of tail feathers, grown on the breeding grounds, was not related to subsequent winter habitat use. Greater covert and tail feather colour (chroma and hue) were correlated, suggesting genetics and/or individual quality played a role in pigment deposition. After controlling for individual difference in tail colour, δ13C values did not explain any variation in greater covert colour, but birds with high δ15N signatures had greater coverts with higher chroma. Male arrival dates varied with tail chroma in Revelstoke and tail hue in Inuvik. Males that arrived early paired with older and/or more colourful mates that initiated clutches earlier, and at one site (Revelstoke) were more likely to fledge young. In addition, in Revelstoke (but not Inuvik) males with high tail hue also acquired more colourful mates. In contrast, after controlling for individual differences in tail colour, greater covert colour did not affect male arrival date, the quality of the mate obtained or reproductive success in either population. CONCLUSIONS: Our results suggest that plumage colour effects on breeding phenology and mate acquisition result from differences in the intrinsic quality of individuals rather than a carry-over effect of winter habitat use.

Using computational approaches to enhance the interpretation of missense variants in the PAX6 gene.

The PAX6 gene encodes a highly-conserved transcription factor involved in eye development. Heterozygous loss-of-function variants in PAX6 can cause a range of ophthalmic disorders including aniridia. A key molecular diagnostic challenge is that many PAX6 missense changes are presently classified as variants of uncertain significance. While computational tools can be used to assess the effect of genetic alterations, the accuracy of their predictions varies. Here, we evaluated and optimised the performance of computational prediction tools in relation to PAX6 missense variants. Through inspection of publicly available resources (including HGMD, ClinVar, LOVD and gnomAD), we identified 241 PAX6 missense variants that were used for model training and evaluation. The performance of ten commonly used computational tools was assessed and a threshold optimization approach was utilized to determine optimal cut-off values. Validation studies were subsequently undertaken using PAX6 variants from a local database. AlphaMissense, SIFT4G and REVEL emerged as the best-performing predictors; the optimized thresholds of these tools were 0.967, 0.025, and 0.772, respectively. Combining the prediction from these top-three tools resulted in lower performance compared to using AlphaMissense alone. Tailoring the use of computational tools by employing optimized thresholds specific to PAX6 can enhance algorithmic performance. Our findings have implications for PAX6 variant interpretation in clinical settings.

Ontogeny of the hominoid scapula: The influence of locomotion on morphology.

Primate shoulder morphology has been linked with locomotor habits, oftentimes irrespective of phylogenetic heritage. Among hominoids, juvenile African apes are known to climb more frequently than adults, while orangutans and gibbons maintain an arboreal lifestyle throughout ontogeny. This study examined if these ontogenetic locomotor differences carry a morphological signal, which should be evident in the scapulae of chimpanzees and gorillas but absent in taxa that do not display ontogenetic behavioral shifts. The scapular morphology of five hominoid primates and one catarrhine outgroup was examined throughout ontogeny to evaluate if scapular traits linked with arboreal activities are modified in response to ontogenetic behavioral shifts away from climbing. Specifically, the following questions were addressed: 1) which scapular characteristics distinguish taxa with different locomotor habits; and 2) do these traits show associated changes during development in taxa known to modify their behavioral patterns? Several traits characterized suspensory taxa from nonsuspensory forms, such as cranially oriented glenohumeral joints, obliquely oriented scapular spines, relatively narrow infraspinous fossae, and inferolaterally expanded subscapularis fossae. The relative shape of the dorsal scapular fossae changed in Pan, Gorilla, and also Macaca in line with predictions based on reported ontogenetic changes in locomotor behavior. These morphological changes were mostly distinct from those seen in Pongo, Hylobates, and Homo and imply a unique developmental pattern, possibly related to ontogenetic locomotor shifts. Accordingly, features that sorted taxa by locomotor habits and changed in concert with ontogenetic behavioral patterns should be particularly useful for reconstructing the locomotor habits of fossil forms.