Evolution of facial muscle anatomy in dogs

Domestication shaped wolves into dogs and transformed both their behavior and their anatomy. Here we show that, in only 33,000 y, domestication transformed the facial muscle anatomy of dogs specifically for facial communication with humans. Based on dissections of dog and wolf heads, we show that the levator anguli oculi medialis, a muscle responsible for raising the inner eyebrow intensely, is uniformly present in dogs but not in wolves. Behavioral data, collected from dogs and wolves, show that dogs produce the eyebrow movement significantly more often and with higher intensity than wolves do, with highest-intensity movements produced exclusively by dogs. Interestingly, this movement increases paedomorphism and resembles an expression that humans produce when sad, so its production in dogs may trigger a nurturing response in humans. We hypothesize that dogs with expressive eyebrows had a selection advantage and that "puppy dog eyes" are the result of selection based on humans' preferences

Children's and adolescents’ evaluations of wealth‐related STEM inequality

This is the final version. Available on open access from Wiley via the DOI in this recordThe fields of science, technology, engineering, and mathematics (STEM) are rife with inequalities and under-representation that have their roots in childhood. While researchers have focused on gender and race/ethnicity as two key dimensions of inequality, less attention has been paid to wealth. To this end, and drawing from the Social Reasoning Development approach, we examined children's and adolescents’ perceptions of STEM ability and access to opportunities as a function of wealth, as well as their desire to rectify such inequalities. Participants (n = 234: early childhood, n = 70, mean age = 6.33, SD =.79; middle childhood, n = 92, mean age = 8.90, SD =.83 and early adolescence, n = 62, mean age = 12.00; SD = 1.16) in the U.K. (64% White British) and U.S. (40% White/European American) read about two characters, one high-wealth and one low-wealth. In early childhood, participants reported that the high-wealth character would have greater STEM ability and were just as likely to invite either character to take part in a STEM opportunity. By middle childhood, participants were more likely to report equal STEM abilities for both characters and to seek to rectify inequalities by inviting the low-wealth character to take part in a STEM opportunity. However, older participants reported that peers would still prefer to invite the high-wealth character. These findings also varied by ethnic group status, with minority status participants rectifying inequalities at a younger age than majority status participants. Together these findings document that children are aware of STEM inequalities based on wealth and, with age, will increasingly seek to rectify these inequalities.National Science Foundation (NSF)Wellcome TrustEconomic and Social Research Council (ESRC

Promoting Diverse Youth's Career Development through Informal Science Learning: The Role of Inclusivity and Belonging

This is the final version. Available on open access from Springer via the DOI in this recordLittle research has examined the associations between perceived inclusivity within informal science learning sites, youth program belonging and perceptions of program career preparation. This study explored relations between these factors at three timepoints (T1 = start of program, T2 = 3 months and T3 = 12 months after start). Participants were a diverse sample of 209 adolescents participating in STEM youth programs within informal science learning sites situated in the United States and United Kingdom (70% females: M age = 15.27, SD age = 1.60), with 53.1% British and 64.1% non-White. Path analysis revealed that only perceptions of inclusivity for own social identity group (i.e., gender, ethnicity) at T1 were associated with T2 STEM youth program belonging. There was a significant indirect effect of T1 perceptions of inclusivity for one's own social identity groups on T3 perceptions of program career preparation via T2 program belonging. This study highlights that, over time, perceptions of inclusivity around youth's own social identity groups (i.e., gender and ethnicity/culture) are related to a sense of youth program belonging, which in turn is later associated with perceptions of program career preparation.National Science Foundation (NSF)Wellcome TrustEconomic and Social Research Council (ESRC

Reciprocal Associations Between Science Efficacy, STEM Identity and Scientist Career Interest Among Adolescent Girls within the Context of Informal Science Learning

This is the final version. Available on open access from Springer via the DOI in this recordLimited research has explored the longitudinal pathway to youth career interests via identity and efficacy together. This study examined the longitudinal associations between science efficacy, STEM (science, technology, engineering and math) identity, and scientist career interest among girls who are historically considered as an underrepresented group among scientists. The sample included 308 girls (M age = 15.22, SD age = 1.66; 42.8% White) from six STEM youth programs, each at a different informal science learning site within the U.K. and the U.S. Longitudinal structural equation modelling demonstrated that science efficacy consistently predicted STEM identity and scientist career interest, and similarly, STEM identity consistently predicted science efficacy over a two-year period. Scientist career interest at 12 months predicted science efficacy at 24 months. The coefficients of efficacy predicting STEM identity and scientist career interest were significantly larger compared to STEM identity and scientist career interest in predicting science efficacy from 12 months to 24 months. Further mediation analysis supported a significant pathway from STEM identity at 3 months to scientist career interest at 24 months via 12-month science efficacy. The findings highlight that science efficacy and STEM identity for girls relate to their scientist career interest and these longitudinal associations are reciprocal. This study suggests that science efficacy and STEM identity mutually influence each other, and enhancing science efficacy and STEM identity is key to promoting adolescents' interest in being a scientist.Wellcome TrustNational Science Foundation (NSF)Economic and Social Research Council (ESRC

Anyone with a Long-Face? Craniofacial Evolutionary Allometry (CREA) in a Family of Short-Faced Mammals, the Felidae

Among adults of closely related species, a trend in craniofacial evolutionary allometry (CREA) for larger taxa to be long-faced and smaller ones to have paedomorphic aspects, such as proportionally smaller snouts and larger braincases, has been demonstrated in some mammals and two bird lineages. Nevertheless, whether this may represent a ‘rule’ with few exceptions is still an open question. In this context, Felidae is a particularly interesting family to study because, although its members are short-faced, previous research did suggest relative facial elongation in larger living representatives. Using geometric morphometrics, based on two sets of anatomical landmarks, and traditional morphometrics, for comparing relative lengths of the palate and basicranium, we performed a series of standard and comparative allometric regressions in the Felidae and its two subfamilies. All analyses consistently supported the CREA pattern, with only one minor exception in the geometric morphometric analysis of Pantherinae: the genus Neofelis. With its unusually long canines, Neofelis species seem to have a relatively narrow cranium and long face, despite being smaller than other big cats. In spite of this, overall, our findings strengthen the possibility that the CREA pattern might indeed be a ‘rule’ among mammals, raising questions on the processes behind it and suggesting future directions for its study

Scaling of forearm muscle weights in primates

Among primates, it has been proposed that the differential development of the forearm flexor compartment is connected to substrate use. Likewise, the projection of the medial epicondyle is thought to reflect this differential development. We examined the scaling properties of forearm muscle wet weights to test the hypothesis that the total masses of various muscle compartments are differentially developed among primates. The forearms of six strepsirrhine (Eulemur fulvus, Lemur catta, Varecia rubra, Hapalemur griseus, Galago senegalensis, Nycticebus coucang) and seven haplorhine (Callithrix jacchus, Macaca sp., Papio sp., Erythrocebus patas, Hylobates lar, Gorilla gorilla, Pan troglodytes) primate specimens were dissected. Distal humerus dimensions and muscle wet weights were measured. Scaling properties of each muscle compartment within the forearm were examined via ordinary least squares regression. The total mass of the flexor and extensor compartments were both found to scale isometrically on total forearm muscle mass, with little unexplained variance (p\0.0001, r250.99). Likewise, the mass of the wrist flexors and digital flexors both scale isometrically to total forearm muscle mass (p\0.0001, r250.98). The mass of the total flexor compartment and the mass of the digital flexors both fail to significantly explain the variance in medial epicondyle projection, when body size is taken into account. It is concluded that the relative masses of the wrist and digital flexors do not predictably vary with substrate use. Locomotor differences in epicondyle development likely serve to reorient the muscles around the joint, rather than reflect any differential development of muscle mass

Correlation of forearm muscle architecture and locomotion patterns in primates

We measured wet mass (MM), linear dimensions, and fiber length (FL) for each antebrachial muscle and calculated physiological cross sectional area (PCSA) for six strepsirrhines, six platyrrhines and seven catarrhines spanning nearly the entire primate body size range (from Galago to Gorilla). These variables were studied for each muscle and across muscles groups (flexors, extensors, and “others” – i.e., supinator, pronators, etc.) using RMA regression (alpha = 0.05). Total forearm (TFor) PCSA is tightly correlated with TFor MM across the whole sample and within each suborder and is slightly positively allometric across the whole sample and within strepsirrhines and catarrhines (but not platyrrhines). Similar correlations and allometry between MM and PCSA are found within the flexor and extensor compartments. However, FL is not highly correlated with total MM variables and instead correlates with locomotor patterns. Thus primate forearm muscles have relatively consistent (though slightly positively allometric) crossections, but vary according to FL, suggesting locomotor adaptations in stretch and flexibility, but not force production. Therefore the variation in the anatomy of the epicondyle likely relates to adaptations for mechanical advantage and not muscle force as has been previously hypothesized