DomArchive: a century of published dominance data

Dominance behaviours have been collected for many groups of animals since 1922 and serve as a foundation for research on social behaviour and social structure. Despite a wealth of data from the last century of research on dominance hierarchies, these data are only rarely used for comparative insight. Here, we aim to facilitate comparative studies of the structure and function of dominance hierarchies by compiling published dominance interaction datasets from the last 100 years of work. This compiled archive includes 436 datasets from 190 studies of 367 unique groups (mean group size 13.8, s.d. = 13.4) of 135 different species, totalling over 243 000 interactions. These data are presented in an R package alongside relevant metadata and a tool for subsetting the archive based on biological or methodological criteria. In this paper, we explain how to use the archive, discuss potential limitations of the data, and reflect on best practices in publishing dominance data based on our experience in assembling this dataset. This archive will serve as an important resource for future comparative studies and will promote the development of general unifying theories of dominance in behavioural ecology that can be grounded in testing with empirical data. This article is part of the theme issue ‘The centennial of the pecking order: current state and future prospects for the study of dominance hierarchies’

Social connections predict brain structure in a multidimensional free-ranging primate society

Reproduction and survival in most primate species reflects management of both competitive and cooperative relationships. Here, we investigated the links between neuroanatomy and sociality in free-ranging rhesus macaques. In adults, the number of social partners predicted the volume of the mid–superior temporal sulcus and ventral-dysgranular insula, implicated in social decision-making and empathy, respectively. We found no link between brain structure and other key social variables such as social status or indirect connectedness in adults, nor between maternal social networks or status and dependent infant brain structure. Our findings demonstrate that the size of specific brain structures varies with the number of direct affiliative social connections and suggest that this relationship may arise during development. These results reinforce proposed links between social network size, biological success, and the expansion of specific brain circuits

Social connections predict brain structure in a multidimensional free-ranging primate society

This is the final version. Available on open access from the American Association for the Advancement of Science via the DOI in this recordData and materials availability: All data, code, and materials used in this study are available on the Open Science Framework platform (osf.io). Link: https://osf.io/xfz3r/?view_only=66633a9490e649038330a98788a0cca3. Original brain tissue samples can be provided by the University of Pennsylvania pending scientific review and a completed material transfer agreement. Requests for brain tissues should be submitted to: [email protected] and survival in most primate species reflects management of both competitive and cooperative relationships. Here, we investigated the links between neuroanatomy and sociality in free-ranging rhesus macaques. In adults, the number of social partners predicted the volume of the mid-superior temporal sulcus and ventral-dysgranular insula, implicated in social decision-making and empathy, respectively. We found no link between brain structure and other key social variables such as social status or indirect connectedness in adults, nor between maternal social networks or status and dependent infant brain structure. Our findings demonstrate that the size of specific brain structures varies with the number of direct affiliative social connections and suggest that this relationship may arise during development. These results reinforce proposed links between social network size, biological success, and the expansion of specific brain circuits

Cognitive performance is linked to group size and affects fitness in Australian magpies

This is the author accepted manuscript. The final version is available from Springer Nature via the DOI in this recordThe social intelligence hypothesis states that the demands of social life drive cognitive evolution. This idea receives support from comparative studies that link variation in group size or mating systems with cognitive and neuroanatomical differences across species, but findings are contradictory and contentious. To understand the cognitive consequences of sociality, it is also important to investigate social variation within species. Here we show that in wild, cooperatively breeding Australian magpies, individuals that live in large groups show increased cognitive performance, which is linked to increased reproductive success. Individual performance was highly correlated across four cognitive tasks, indicating a 'general intelligence factor' that underlies cognitive performance. Repeated cognitive testing of juveniles at different ages showed that the correlation between group size and cognition emerged in early life, suggesting that living in larger groups promotes cognitive development. Furthermore, we found a positive association between the task performance of females and three indicators of reproductive success, thus identifying a selective benefit of greater cognitive performance. Together, these results provide intraspecific evidence that sociality can shape cognitive development and evolution.This work was funded by an ARC Discovery grant awarded to A.R.R., A.T. and M. B. V. Bell, and a University of Western Australia International Postgraduate Research Scholarship and Endeavour Research Fellowship awarded to B.J.A. A.T. received additional support from a BBSRC David Phillips Fellowship (BB/H021817/1)

Perspective: Measuring Sweetness in Foods, Beverages, and Diets: Toward Understanding the Role of Sweetness in Health.

Various global public health agencies recommend minimizing exposure to sweet-tasting foods or beverages. The underlying rationale is that reducing exposure to the perception of sweet tastes, without regard to the source of sweetness, may reduce preferences for sweetness, added sugar intake, caloric intake, and body weight. However, the veracity of this sequence of outcomes has yet to be documented, as revealed by findings from recent systematic reviews on the topic. Efforts to examine and document the effects of sweetness exposure are needed to support evidence-based recommendations. They require a generally agreed-upon methodology for measuring sweetness in foods, beverages, and the overall diet. Although well-established sensory evaluation techniques exist for individual foods in laboratory settings, they are expensive and time-consuming, and agreement on the optimal approach for measuring the sweetness of the total diet is lacking. If such a measure could be developed, it would permit researchers to combine data from different studies and populations and facilitate the design and conduct of new studies to address unresolved research questions about dietary sweetness. This narrative review includes an overview of available sensory techniques, their strengths and limitations, recent efforts to measure the sweetness of foods and diets across countries and cultures, and a proposed future direction for improving methods for measuring sweetness toward developing the data required to support evidence-based recommendations around dietary sweetness

Greater variability in rhesus macaque (Macaca mulatta) endocranial volume among males

The greater male variability hypothesis posits that males exhibit more physical and behavioral variability than females. This pattern is observed across mammalian species and is especially pronounced in sexually selected traits. Greater variability in males likely reflects some combination of evolutionary mechanisms (e.g. balancing or disruptive selection) and developmental mechanisms (e.g. sexually dimorphic developmental schedules) that produce and maintain inter-individual variability. However, research investigating this phenomenon in brain size and structure is almost exclusive to humans. To address this gap in knowledge, we investigate sex differences in variability and heritability of relative and absolute endocranial volume (ECV) in a pedigreed sample of 542 (300F/242M) rhesus macaques using generalized linear mixed models that control for pairwise relatedness (i.e. an ‘animal model’). We found that males display more variable relative ECVs (phenotypic variance: male mean=0.646 [0.578,0.693], female mean=0.503 [0.457,0.540]) and absolute ECVs (phenotypic variance: male mean=0.670 [0.598,0.717], female mean=0.533 [0.481,0.568]). These findings are consistent with research in humans and chimpanzees. However, males do not display significantly lower heritability estimates and sex differences in phenotypic variance are not driven by environmental variance for relative (heritability: female mean=0.658 [0.568,0.778], male mean=0.626 [0.522,0.809]; environmental: female mean=0.171 [0.109,0.211], male mean=0.241 [0.119,0.302]) or absolute (heritability: female mean=0.683 [0.613,0.806], male mean=0.667 [0.578,0.827]; environmental: female mean=0.168 [0.112,0.210], male mean=0.223 [0.115,0.283]) ECV. These results suggest that, in rhesus macaques, greater male variability in brain size is likely driven by balancing or disruptive selection, rather than greater susceptibility to environmental effects during their relatively extended development.Othe

Understanding the human brain: insights from comparative biology

Human brains are exceptionally large, support distinctive cognitive processes, and evolved by natural selection to mediate adaptive behavior. Comparative biology situates the human brain in evolutionary context to illuminate how it has been shaped by selection and how its structure relates to evolutionary function, while identifying the developmental and molecular changes that were involved. Recent applications of powerful phylogenetic methods have made new findings, some of which overturn conventional wisdom about how brains evolve. Here, we focus on four long-standing claims about brain evolution, and discuss how new work has either contradicted them or shown them to be much more complicated than previously appreciated. Throughout, we emphasize studies of nonhuman primates and hominins, our recent ancestors and close relatives

Evolution_DeCasien et al_Supplementary Data

This excel file contains all data used in the manuscript "Encephalization and longevity evolved in a correlated fashion in Euarchontoglires but not in other mammals". Specifically, this data set contains maximum lifespans, species average brain weights, and species average body weights for more than 600 mammalian species, including 151 carnivorans (Carnivora), 77 even-toed ungulates (Artiodactyla), 37 cetaceans (Cetacea), and 54 chiropterans (Chiroptera) among Laurasiatheria, and 168 rodents (Rodentia), 10 lagomorphs (Lagomorpha), 3 tree shrews (Scandentia), and 144 primates (Primates) among Euarchontoglires

Data from: Encephalization and longevity evolved in a correlated fashion in Euarchontoglires but not in other mammals

Across mammals, encephalization and longevity show a strong correlation. It is not clear, however, whether these traits evolved in a correlated fashion within mammalian orders, or when they do, whether one trait drives changes in the other. Here, we compare independent and correlated evolutionary models to identify instances of correlated evolution within six mammalian orders. In cases of correlated evolution, we subsequently examined transition patterns between small/large relative brain size and short/long lifespan. In four mammalian orders, these traits evolved independently. This may reflect constraints related to energy allocation, predation avoidance tactics, and reproductive strategies. Within both primates and rodents, and their parent clade Euarchontoglires, we found evidence for correlated evolution. In primates, transition patterns suggest relatively larger brains likely facilitated the evolution of long lifespans. Because larger brains prolong development and reduce fertility rates, they may be compensated for with longer lifespans. Furthermore, encephalization may enable cognitively-complex strategies that reduce extrinsic mortality. Rodents show an inverse pattern of correlated evolution, whereby long lifespans appear to have facilitated the evolution of relatively larger brains. This may be because longer-lived organisms have more to gain from investment in encephalization. Together, our results provide evidence for the correlated evolution of encephalization and longevity, but only in some mammalian orders